AI Trajectory

null

{
  "EnableConfigs": [
    "BLOCK"
  ],
  "FocusSymbols": [
    "blkdev_fallocate",
    "blkdev_issue_zeroout",
    "bio_submit_or_kill"
  ],
  "KMSANReasoning": "The patch modifies `blkdev_fallocate` in `block/fops.c` to include the `BLKDEV_ZERO_KILLABLE` flag when calling `blkdev_issue_zeroout()`. This allows zeroing operations on block devices to be interrupted by fatal signals.\n\nThe modification only alters an integer flags parameter passed into an existing function. It does not introduce, allocate, or modify any buffers, structures, padding, or data copied to userspace, nor does it affect any bounds checks or logic dealing with uninitialized memory. Therefore, there is no risk of uninitialized memory reads or info-leaks, and a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch modifies blkdev_fallocate() to include the BLKDEV_ZERO_KILLABLE flag when issuing zeroouts on block devices. This alters control flow and bio submission handling when fatal signals are pending, making the operation interruptible. This affects reachable core block layer functionality exerciseable via the fallocate syscall on block devices.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit ee9c5db58bfed74ccd756b49c26190ff92f6a18f\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Mon Sep 28 10:59:23 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/block/fops.c b/block/fops.c\nindex 2ce7c6c4714e4..a2fe27d8ceff1 100644\n--- a/block/fops.c\n+++ b/block/fops.c\n@@ -909,7 +909,8 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,\n \t\tgoto fail;\n \n \terror = blkdev_issue_zeroout(bdev, start \u003e\u003e SECTOR_SHIFT,\n-\t\t\t\t     len \u003e\u003e SECTOR_SHIFT, GFP_KERNEL, flags);\n+\t\t\t\t     len \u003e\u003e SECTOR_SHIFT, GFP_KERNEL,\n+\t\t\t\t     flags | BLKDEV_ZERO_KILLABLE);\n  fail:\n \tfilemap_invalidate_unlock(inode-\u003ei_mapping);\n \tinode_unlock(inode);\n"
}

core

null

{
  "EnableConfigs": [
    "BLOCK"
  ],
  "FocusSymbols": [
    "blkdev_fallocate",
    "blkdev_issue_zeroout",
    "bio_submit_or_kill"
  ],
  "Reasoning": "The patch modifies blkdev_fallocate() to include the BLKDEV_ZERO_KILLABLE flag when issuing zeroouts on block devices. This alters control flow and bio submission handling when fatal signals are pending, making the operation interruptible. This affects reachable core block layer functionality exerciseable via the fallocate syscall on block devices.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer and security engineer.
Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on internal assumptions. You must actively use your code access
tools to inspect the actual source code, callers, and surrounding context.

================================================================================
1. CORE TRIAGE PHILOSOPHY
================================================================================
The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs,
and newly triggered assertions introduced by the patch series.

- REACHABILITY IS THE PRIMARY GATE:
  Fuzzing can only discover bugs in code that can actually execute in standard virtualized
  environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap).
  If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed,
  regardless of whether it adds assertions or complex logic.

- DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS:
  Patch authors routinely label changes as "cleanups", "refactorings", or state
  "No functional change intended". Do NOT take these claims at face value.
  Code refactorings that rearrange logic, introduce helper functions, or alter state management
  in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs.
  If reachable executable code is modified or refactored, it MUST be fuzzed.

- NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED:
  When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON*, VM_WARN_ON*,
  BUG_ON*, lockdep_assert*) in reachable code paths, it enforces new or stricter invariants.
  Even if the author believes the invariant always holds, fuzzing is essential to verify whether
  an unusual sequence of operations can violate it.

================================================================================
2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA)
================================================================================
Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories:

- Non-kernel and non-executable changes:
  * Modifications to Documentation/, comments, or spelling fixes.
  * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/)
    that do not affect the compiled kernel image (vmlinux) or kernel modules.
  * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints
    that do not alter control flow or data structures.
  * Build system or Kconfig changes that do not alter compiled C logic.
- Structurally unreachable hardware:
  * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed,
    ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU.
- Unreachable execution paths:
  * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during
    physical PCI hot-unplug or manual sysfs driver unbinding.
  * Code paths exclusive to architectures other than the target architecture.

================================================================================
3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA)
================================================================================
Return WorthFuzzing=true whenever the patch touches reachable executable code, including:
- Core Subsystems:
  * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/),
    BPF, scheduler, core networking, VFS, or syscall handling.
- Refactorings and Code Cleanups:
  * Any restructuring of reachable data structures, helper abstractions, or algorithm flows.
- Runtime Assertions and Defensive Checks:
  * Any introduction or alteration of assertions (WARN_ON*, VM_WARN_ON*, BUG_ON*, etc.) in reachable paths.
- Reachable Drivers and Protocols:
  * Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.).

================================================================================
4. EXTRACTING FocusSymbols (PREVENTING DILUTION)
================================================================================
When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer:

- AVOID UBIQUITOUS LIFECYCLE HOT-PATHS:
  Do NOT list generic, ubiquitous functions called by almost every program in the corpus
  (including, but not limited to: general memory allocators and deallocators, page fault
  and trap handlers, or core synchronization primitives; this is not an exhaustive list).
  Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused",
  which severely dilutes fuzzing effort away from the actual changes.

- TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS:
  List functions that specifically implement the logic being added or altered, or direct API entrypoints
  for the subsystem feature under review.

- HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h):
  Compiler-inlined static functions (such as static inlines in mm/*.h or include/linux/*.h) lack
  distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters.
  If the changes are primarily in static inline helpers, identify non-static, feature-specific caller
  functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers).

================================================================================
5. IDENTIFYING EnableConfigs
================================================================================
Identify any specific CONFIG_ options required to properly compile and reach the modified code:
- Inspect Kconfig files and #ifdef guards; do not make assumptions.
- Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed.
- Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit ee9c5db58bfed74ccd756b49c26190ff92f6a18f
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Sep 28 10:59:23 2026 +0000

    syz-cluster: applied patch under review

diff --git a/block/fops.c b/block/fops.c
index 2ce7c6c4714e4..a2fe27d8ceff1 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -909,7 +909,8 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 		goto fail;
 
 	error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
-				     len >> SECTOR_SHIFT, GFP_KERNEL, flags);
+				     len >> SECTOR_SHIFT, GFP_KERNEL,
+				     flags | BLKDEV_ZERO_KILLABLE);
  fail:
 	filemap_invalidate_unlock(inode->i_mapping);
 	inode_unlock(inode);

gemini-3.8-flash

null

null

							input: 2876
							output: 34
							thoughts: 265
						

**Analyzing a Block Device Fallocate Patch**

Okay, let's dive into this patch. My initial assessment is that it looks like a targeted fix within `block/fops.c`, specifically concerning the `blkdev_fallocate` function. It seems to be related to handling the `fallocate` system call, which is used for preallocating disk space and potentially zeroing it out.

The `diff` output is clear. The key change is on line 909, where `blkdev_issue_zeroout` is being called. Previously, the `flags` parameter passed to this function was simply `GFP_KERNEL`. Now, the patch modifies this to `flags | BLKDEV_ZERO_KILLABLE`.

My immediate thought is, what exactly does `BLKDEV_ZERO_KILLABLE` signify? I need to understand the implications of this bit being set. Is it a safety mechanism? Does it make the zeroing operation interruptible, or allow it to be killed under certain conditions? What are the performance trade-offs? Does this introduce any potential for data corruption if interrupted?

To properly contextualize this, I need to read the code surrounding this change and potentially trace back through the `blkdev_issue_zeroout` function to understand how the new flag impacts its behavior. I’ll need to examine how the `flags` parameter is used within that function and whether `BLKDEV_ZERO_KILLABLE` is handled consistently across different block device drivers. I'll probably start with a quick `read-file` or `grepper` inspection of `block/fops.c` around line 909, and then trace from there to clarify the logic.

{
  "File": "block/fops.c",
  "FirstLine": 880,
  "LineCount": 50
}

{
  "Contents": " 880:\t\t */\n 881:\t\tif ((start | len) \u0026 (bdev_logical_block_size(bdev) - 1))\n 882:\t\t\treturn -EINVAL;\n 883:\t\n 884:\t\tinode_lock(inode);\n 885:\t\tfilemap_invalidate_lock(inode-\u003ei_mapping);\n 886:\t\n 887:\t\tswitch (mode) {\n 888:\t\tcase FALLOC_FL_ZERO_RANGE:\n 889:\t\tcase FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:\n 890:\t\t\tflags = BLKDEV_ZERO_NOUNMAP;\n 891:\t\t\tbreak;\n 892:\t\tcase FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:\n 893:\t\t\tflags = BLKDEV_ZERO_NOFALLBACK;\n 894:\t\t\tbreak;\n 895:\t\tcase FALLOC_FL_WRITE_ZEROES:\n 896:\t\t\tflags = 0;\n 897:\t\t\tbreak;\n 898:\t\tdefault:\n 899:\t\t\terror = -EOPNOTSUPP;\n 900:\t\t\tgoto fail;\n 901:\t\t}\n 902:\t\n 903:\t\t/*\n 904:\t\t * Invalidate the page cache, including dirty pages, for valid\n 905:\t\t * de-allocate mode calls to fallocate().\n 906:\t\t */\n 907:\t\terror = truncate_bdev_range(bdev, file_to_blk_mode(file), start, end);\n 908:\t\tif (error)\n 909:\t\t\tgoto fail;\n 910:\t\n 911:\t\terror = blkdev_issue_zeroout(bdev, start \u003e\u003e SECTOR_SHIFT,\n 912:\t\t\t\t\t     len \u003e\u003e SECTOR_SHIFT, GFP_KERNEL,\n 913:\t\t\t\t\t     flags | BLKDEV_ZERO_KILLABLE);\n 914:\t fail:\n 915:\t\tfilemap_invalidate_unlock(inode-\u003ei_mapping);\n 916:\t\tinode_unlock(inode);\n 917:\t\treturn error;\n 918:\t}\n 919:\t\n 920:\tstatic int blkdev_mmap_prepare(struct vm_area_desc *desc)\n 921:\t{\n 922:\t\tstruct file *file = desc-\u003efile;\n 923:\t\n 924:\t\tif (bdev_read_only(I_BDEV(bdev_file_inode(file))))\n 925:\t\t\treturn generic_file_readonly_mmap_prepare(desc);\n 926:\t\n 927:\t\treturn generic_file_mmap_prepare(desc);\n 928:\t}\n 929:\t\n"
}

gemini-3.8-flash

null

null

							input: 4266
							output: 21
							thoughts: 162
						

**Analyzing the `blkdev_fallocate` Path and the Impact of `BLKDEV_ZERO_KILLABLE`**

Okay, so I'm digging into `blkdev_fallocate` in `block/fops.c`. Right, this is the function handling `fallocate()` for block devices – things like `/dev/loop0`, `/dev/nullb0`, `/dev/ram0`, and so on. It's the standard call sequence: `vfs_fallocate` hits `file->f_op->fallocate`, and that gets me here.

What's grabbing my attention is how `blkdev_issue_zeroout` is being called within `blkdev_fallocate`. Specifically, that `flags` are being passed, but now with `| BLKDEV_ZERO_KILLABLE` added in. That addition is key. I need to understand what that flag does.

The crucial next step is to trace how `BLKDEV_ZERO_KILLABLE` is actually handled within `blkdev_issue_zeroout`. That's where the real impact of this change will become clear. I need to see what's being modified, what conditional paths are being taken, and how the zeroing operation is actually behaving with this new flag enabled.

{
  "Expression": "BLKDEV_ZERO_KILLABLE"
}

{
  "Output": "block/bio.c=1613=int bio_submit_or_kill(struct bio *bio, unsigned int flags)\nblock/bio.c-1614-{\nblock/bio.c:1615:\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026 fatal_signal_pending(current)) {\nblock/bio.c-1616-\t\tbio_await(bio, NULL, bio_endio_cb);\n--\nblock/blk-lib.c=119=static void __blkdev_issue_write_zeroes(struct block_device *bdev,\n--\nblock/blk-lib.c-127-\nblock/blk-lib.c:128:\t\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026\nblock/blk-lib.c-129-\t\t    fatal_signal_pending(current))\n--\nblock/blk-lib.c=187=static void __blkdev_issue_zero_pages(struct block_device *bdev,\n--\nblock/blk-lib.c-196-\nblock/blk-lib.c:197:\t\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026\nblock/blk-lib.c-198-\t\t    fatal_signal_pending(current))\n--\nblock/fops.c=845=static long blkdev_fallocate(struct file *file, int mode, loff_t start,\n--\nblock/fops.c-912-\t\t\t\t     len \u003e\u003e SECTOR_SHIFT, GFP_KERNEL,\nblock/fops.c:913:\t\t\t\t     flags | BLKDEV_ZERO_KILLABLE);\nblock/fops.c-914- fail:\n--\nblock/ioctl.c=122=static int blk_ioctl_discard(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-164-\tif (prev) {\nblock/ioctl.c:165:\t\terr = bio_submit_or_kill(prev, BLKDEV_ZERO_KILLABLE);\nblock/ioctl.c-166-\t\tif (err == -EOPNOTSUPP)\n--\nblock/ioctl.c=211=static int blk_ioctl_zeroout(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-244-\terr = blkdev_issue_zeroout(bdev, start \u003e\u003e 9, len \u003e\u003e 9, GFP_KERNEL,\nblock/ioctl.c:245:\t\t\t\t   BLKDEV_ZERO_NOUNMAP | BLKDEV_ZERO_KILLABLE);\nblock/ioctl.c-246-\n--\ninclude/linux/blkdev.h=1191=int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector,\n--\ninclude/linux/blkdev.h-1195-#define BLKDEV_ZERO_NOFALLBACK\t(1 \u003c\u003c 1)  /* don't write explicit zeroes */\ninclude/linux/blkdev.h:1196:#define BLKDEV_ZERO_KILLABLE\t(1 \u003c\u003c 2)  /* interruptible by fatal signals */\ninclude/linux/blkdev.h-1197-\n"
}

gemini-3.8-flash

null

null

							input: 5515
							output: 35
							thoughts: 426
						

**Analyzing a Patch: A Quick Deep Dive**

Okay, so I need to understand what this patch does. My initial instinct is to quickly check the commit message using `git log -1` to get a high-level view, or at least look at the HEAD commit's message. Wait, I can't run `git log` directly, but the commit info is right here in the prompt! That saves me a step. The commit message tells me it's a "syz-cluster: applied patch under review". Not super informative on its own, but it's a starting point.

Looking at the diff itself, the change is adding `BLKDEV_ZERO_KILLABLE` to the `blkdev_issue_zeroout` call in `block/fops.c`. Specifically, it's modifying the `fallocate` implementation. My next step? I need to understand what this flag actually *does*. I'll need to dig into the surrounding code to determine how `BLKDEV_ZERO_KILLABLE` impacts the behavior of `blkdev_issue_zeroout`. I'm going to check `block/bio.c` around line 1613 and `block/blk-lib.c` around lines 120 and 187, as that seems like a likely location for the flag's definition and usage to determine how this affects the zeroing operation, especially in the context of `fallocate`. I'm expecting to see how this flag interacts with potential error handling or cancellation scenarios.

{
  "File": "block/blk-lib.c",
  "FirstLine": 115,
  "LineCount": 50
}

{
  "Contents": " 115:\t * to media. As a result, write_zeroes is enabled by default and will be\n 116:\t * disabled if a zeroing operation subsequently fails. This means that this\n 117:\t * queue limit is likely to change at runtime.\n 118:\t */\n 119:\tstatic void __blkdev_issue_write_zeroes(struct block_device *bdev,\n 120:\t\t\tsector_t sector, sector_t nr_sects, gfp_t gfp_mask,\n 121:\t\t\tstruct bio **biop, unsigned flags, sector_t limit)\n 122:\t{\n 123:\t\n 124:\t\twhile (nr_sects) {\n 125:\t\t\tunsigned int len = min(nr_sects, limit);\n 126:\t\t\tstruct bio *bio;\n 127:\t\n 128:\t\t\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026\n 129:\t\t\t    fatal_signal_pending(current))\n 130:\t\t\t\tbreak;\n 131:\t\n 132:\t\t\tbio = bio_alloc(bdev, 0, REQ_OP_WRITE_ZEROES, gfp_mask);\n 133:\t\t\tbio-\u003ebi_iter.bi_sector = sector;\n 134:\t\t\tif (flags \u0026 BLKDEV_ZERO_NOUNMAP)\n 135:\t\t\t\tbio-\u003ebi_opf |= REQ_NOUNMAP;\n 136:\t\n 137:\t\t\tbio-\u003ebi_iter.bi_size = len \u003c\u003c SECTOR_SHIFT;\n 138:\t\t\t*biop = bio_chain_and_submit(*biop, bio);\n 139:\t\n 140:\t\t\tnr_sects -= len;\n 141:\t\t\tsector += len;\n 142:\t\t\tcond_resched();\n 143:\t\t}\n 144:\t}\n 145:\t\n 146:\tstatic int blkdev_issue_write_zeroes(struct block_device *bdev, sector_t sector,\n 147:\t\t\tsector_t nr_sects, gfp_t gfp, unsigned flags)\n 148:\t{\n 149:\t\tsector_t limit = bio_write_zeroes_limit(bdev);\n 150:\t\tstruct bio *bio = NULL;\n 151:\t\tstruct blk_plug plug;\n 152:\t\tint ret = 0;\n 153:\t\n 154:\t\tblk_start_plug(\u0026plug);\n 155:\t\t__blkdev_issue_write_zeroes(bdev, sector, nr_sects, gfp, \u0026bio,\n 156:\t\t\t\tflags, limit);\n 157:\t\tif (bio) {\n 158:\t\t\tret = bio_submit_or_kill(bio, flags);\n 159:\t\t\tbio_put(bio);\n 160:\t\t}\n 161:\t\tblk_finish_plug(\u0026plug);\n 162:\t\n 163:\t\t/*\n 164:\t\t * For some devices there is no non-destructive way to verify whether\n"
}

gemini-3.8-flash

null

null

							input: 7096
							output: 34
							thoughts: 21
						

Okay, let's dive into this. Here's my understanding, presented as a personal thought process, given my expertise:

**Examining `bio_submit_or_kill` in `block/bio.c`**

Right, so I need to understand how the block layer handles BIO submission and potential failure scenarios, and `bio_submit_or_kill` seems like a key function for this. I immediately think: "Okay, `bio_submit_or_kill`. The name itself is fairly descriptive, suggesting a critical decision point." My expertise tells me that this function probably sits at the heart of the block I/O path, possibly determining whether a BIO is successfully dispatched to the underlying storage or, in the case of some error, discarded or requeued, potentially with some kind of error handling. I'll need to look closely at what criteria trigger a "kill" versus a "submit." I'm mentally parsing the name, imagining the control flow - is it a simple if/else, or is there more involved logic? The "or" in the name suggests that there's a fork in the path. I'll need to dissect the code to understand the branching conditions, particularly any checks for device health, resource availability, or other error indicators. What are the specific failure scenarios handled here? Is this the function where timeouts are managed? Are there subtle race conditions or concurrency issues that might lead to dropped BIOs? I'll probably be focusing on the arguments passed to it, the internal state it updates, and the functions it calls to understand the intricacies of how errors are managed at this level. Let's see what's in there...

{
  "File": "block/bio.c",
  "FirstLine": 1610,
  "LineCount": 25
}

{
  "Contents": "1610:\t * Submit @bio synchronously, or call bio_endio on it if the current process\n1611:\t * is being killed.\n1612:\t */\n1613:\tint bio_submit_or_kill(struct bio *bio, unsigned int flags)\n1614:\t{\n1615:\t\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026 fatal_signal_pending(current)) {\n1616:\t\t\tbio_await(bio, NULL, bio_endio_cb);\n1617:\t\t\treturn -EINTR;\n1618:\t\t}\n1619:\t\n1620:\t\treturn submit_bio_wait(bio);\n1621:\t}\n1622:\t\n1623:\t/**\n1624:\t * bdev_rw_virt - synchronously read into / write from kernel mapping\n1625:\t * @bdev:\tblock device to access\n1626:\t * @sector:\tsector to access\n1627:\t * @data:\tdata to read/write\n1628:\t * @len:\tlength in byte to read/write\n1629:\t * @op:\t\toperation (e.g. REQ_OP_READ/REQ_OP_WRITE)\n1630:\t *\n1631:\t * Performs synchronous I/O to @bdev for @data/@len.  @data must be in\n1632:\t * the kernel direct mapping and not a vmalloc address.\n1633:\t */\n1634:\tint bdev_rw_virt(struct block_device *bdev, sector_t sector, void *data,\n"
}

gemini-3.8-flash

null

null

							input: 7923
							output: 24
							thoughts: 628
						

**My Fuzzing Assessment**

Okay, time to make a decision. Let's run through the triage criteria again. The primary goal is to find crashes, regressions, and exposed bugs. Reachability is the core concept. If it's not executable in a standard environment, it's out. "No Functional Change" claims and refactorings require careful scrutiny. New or modified assertions in reachable code *must* be fuzzed.

Now, let's apply this to the patch at hand. It's touching `block/fops.c`, specifically `blkdev_fallocate()`.  The key question: is `blkdev_fallocate` reachable in the standard environments we are using, like QEMU or GCE? Absolutely, yes! Any block device – virtio-blk, loop, even a ramdisk or null block device – that is opened and used with `fallocate()` will exercise it.

Does the patch modify *executable* code? Yes, it does. It's now passing `BLKDEV_ZERO_KILLABLE` to `blkdev_issue_zeroout()`.  This changes control flow when a fatal signal is pending during zeroing out of a block device.  This changes how the system interacts with signals, potential early aborts, interaction with bio submissions and unlocks, etc.

Considering the changes, this touches a core subsystem: the block layer, specifically the VFS block device file operations.

Therefore, following the criteria, `WorthFuzzing` is unequivocally `true`.  Now, just to be thorough and to double-check that this file is included, I will consult the `block/Makefile`.

{
  "Expression": "fops",
  "PathPrefix": "block/"
}

{
  "Output": "block/Makefile=6=CONTEXT_ANALYSIS := y\nblock/Makefile-7-\nblock/Makefile:8:obj-y\t\t:= bdev.o fops.o bio.o elevator.o blk-core.o blk-sysfs.o \\\nblock/Makefile-9-\t\t\tblk-flush.o blk-settings.o blk-ioc.o blk-map.o \\\n--\nblock/bdev.c=761=static void blkdev_put_whole(struct block_device *bdev)\n--\nblock/bdev.c-764-\t\tblkdev_flush_mapping(bdev);\nblock/bdev.c:765:\tif (bdev-\u003ebd_disk-\u003efops-\u003erelease)\nblock/bdev.c:766:\t\tbdev-\u003ebd_disk-\u003efops-\u003erelease(bdev-\u003ebd_disk);\nblock/bdev.c-767-}\n--\nblock/bdev.c=769=static int blkdev_get_whole(struct block_device *bdev, blk_mode_t mode)\n--\nblock/bdev.c-773-\nblock/bdev.c:774:\tif (disk-\u003efops-\u003eopen) {\nblock/bdev.c:775:\t\tret = disk-\u003efops-\u003eopen(disk, mode);\nblock/bdev.c-776-\t\tif (ret) {\n--\nblock/bdev.c=971=int bdev_open(struct block_device *bdev, blk_mode_t mode, void *holder,\n--\nblock/bdev.c-993-\t\tgoto abort_claiming;\nblock/bdev.c:994:\tif (!try_module_get(disk-\u003efops-\u003eowner))\nblock/bdev.c-995-\t\tgoto abort_claiming;\n--\nblock/bdev.c-1039-put_module:\nblock/bdev.c:1040:\tmodule_put(disk-\u003efops-\u003eowner);\nblock/bdev.c-1041-abort_claiming:\n--\nblock/bdev.c=1079=struct file *bdev_file_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,\n--\nblock/bdev.c-1096-\tbdev_file = alloc_file_pseudo_noaccount(BD_INODE(bdev),\nblock/bdev.c:1097:\t\t\tblockdev_mnt, \"\", flags | O_LARGEFILE, \u0026def_blk_fops);\nblock/bdev.c-1098-\tif (IS_ERR(bdev_file)) {\n--\nblock/bdev.c=1153=void bdev_release(struct file *bdev_file)\n--\nblock/bdev.c-1191-\nblock/bdev.c:1192:\tmodule_put(disk-\u003efops-\u003eowner);\nblock/bdev.c-1193-put_no_open:\n--\nblock/bdev.c=1238=void bdev_fput(struct file *bdev_file)\nblock/bdev.c-1239-{\nblock/bdev.c:1240:\tif (WARN_ON_ONCE(bdev_file-\u003ef_op != \u0026def_blk_fops))\nblock/bdev.c-1241-\t\treturn;\n--\nblock/blk-core.c=670=static void __submit_bio(struct bio *bio)\n--\nblock/blk-core.c-680-\t\telse\nblock/blk-core.c:681:\t\t\tdisk-\u003efops-\u003esubmit_bio(bio);\nblock/blk-core.c-682-\t\tblk_queue_exit(disk-\u003equeue);\n--\nblock/blk-core.c=982=int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags)\n--\nblock/blk-core.c-1015-\t\tif ((q-\u003elimits.features \u0026 BLK_FEAT_POLL) \u0026\u0026 disk \u0026\u0026\nblock/blk-core.c:1016:\t\t    disk-\u003efops-\u003epoll_bio)\nblock/blk-core.c:1017:\t\t\tret = disk-\u003efops-\u003epoll_bio(bio, iob, flags);\nblock/blk-core.c-1018-\t}\n--\nblock/blk-mq-debugfs.c=583=static int blk_mq_debugfs_release(struct inode *inode, struct file *file)\n--\nblock/blk-mq-debugfs.c-592-\nblock/blk-mq-debugfs.c:593:static const struct file_operations blk_mq_debugfs_fops = {\nblock/blk-mq-debugfs.c-594-\t.open\t\t= blk_mq_debugfs_open,\n--\nblock/blk-mq-debugfs.c=624=static void debugfs_create_files(struct request_queue *q, struct dentry *parent,\n--\nblock/blk-mq-debugfs.c-640-\t\tdebugfs_create_file_aux(attr-\u003ename, attr-\u003emode, parent,\nblock/blk-mq-debugfs.c:641:\t\t\t\t    (void *)attr, data, \u0026blk_mq_debugfs_fops);\nblock/blk-mq-debugfs.c-642-}\n--\nblock/blk-zoned.c=227=static int blkdev_do_report_zones(struct block_device *bdev, sector_t sector,\n--\nblock/blk-zoned.c-232-\nblock/blk-zoned.c:233:\tif (!bdev_is_zoned(bdev) || WARN_ON_ONCE(!disk-\u003efops-\u003ereport_zones))\nblock/blk-zoned.c-234-\t\treturn -EOPNOTSUPP;\n--\nblock/blk-zoned.c-238-\nblock/blk-zoned.c:239:\treturn disk-\u003efops-\u003ereport_zones(disk, sector, nr_zones, args);\nblock/blk-zoned.c-240-}\n--\nblock/blk-zoned.c=1043=int blkdev_report_zones_cached(struct block_device *bdev, sector_t sector,\n--\nblock/blk-zoned.c-1053-\tif (!cb || !bdev_is_zoned(bdev) ||\nblock/blk-zoned.c:1054:\t    WARN_ON_ONCE(!disk-\u003efops-\u003ereport_zones))\nblock/blk-zoned.c-1055-\t\treturn -EOPNOTSUPP;\n--\nblock/blk-zoned.c=1741=static bool disk_zone_wplug_submit_bio(struct gendisk *disk,\n--\nblock/blk-zoned.c-1782-\tif (bdev_test_flag(bdev, BD_HAS_SUBMIT_BIO)) {\nblock/blk-zoned.c:1783:\t\tbdev-\u003ebd_disk-\u003efops-\u003esubmit_bio(bio);\nblock/blk-zoned.c-1784-\t\tblk_queue_exit(bdev-\u003ebd_disk-\u003equeue);\n--\nblock/blk-zoned.c=2314=int blk_revalidate_disk_zones(struct gendisk *disk)\n--\nblock/blk-zoned.c-2353-\nblock/blk-zoned.c:2354:\tret = disk-\u003efops-\u003ereport_zones(disk, 0, UINT_MAX, \u0026rep_args);\nblock/blk-zoned.c-2355-\tif (!ret) {\n--\nblock/blk-zoned.c=2405=int blk_zone_issue_zeroout(struct block_device *bdev, sector_t sector,\n--\nblock/blk-zoned.c-2423-\t */\nblock/blk-zoned.c:2424:\tret = disk-\u003efops-\u003ereport_zones(disk, sector, 1, NULL);\nblock/blk-zoned.c-2425-\tif (ret != 1)\n--\nblock/bsg.c=172=static int bsg_uring_cmd(struct io_uring_cmd *ioucmd, unsigned int issue_flags)\n--\nblock/bsg.c-188-\nblock/bsg.c:189:static const struct file_operations bsg_fops = {\nblock/bsg.c-190-\t.open\t\t=\tbsg_open,\n--\nblock/bsg.c=218=struct bsg_device *bsg_register_queue(struct request_queue *q,\n--\nblock/bsg.c-247-\nblock/bsg.c:248:\tcdev_init(\u0026bd-\u003ecdev, \u0026bsg_fops);\nblock/bsg.c-249-\tbd-\u003ecdev.owner = THIS_MODULE;\n--\nblock/disk-events.c=184=static void disk_check_events(struct disk_events *ev,\n--\nblock/disk-events.c-192-\t/* check events */\nblock/disk-events.c:193:\tevents = disk-\u003efops-\u003echeck_events(disk, clearing);\nblock/disk-events.c-194-\n--\nblock/disk-events.c=433=int disk_alloc_events(struct gendisk *disk)\n--\nblock/disk-events.c-436-\nblock/disk-events.c:437:\tif (!disk-\u003efops-\u003echeck_events || !disk-\u003eevents)\nblock/disk-events.c-438-\t\treturn 0;\n--\nblock/error-injection.c=294=static int blk_error_injection_release(struct inode *inode, struct file *file)\n--\nblock/error-injection.c-298-\nblock/error-injection.c:299:static const struct file_operations blk_error_injection_fops = {\nblock/error-injection.c-300-\t.owner\t\t= THIS_MODULE,\n--\nblock/error-injection.c=307=void blk_error_injection_init(struct gendisk *disk)\n--\nblock/error-injection.c-309-\tdebugfs_create_file(\"error_injection\", 0600, disk-\u003equeue-\u003edebugfs_dir,\nblock/error-injection.c:310:\t\t\tdisk, \u0026blk_error_injection_fops);\nblock/error-injection.c-311-}\n--\nblock/fops.c=920=static int blkdev_mmap_prepare(struct vm_area_desc *desc)\n--\nblock/fops.c-929-\nblock/fops.c:930:const struct file_operations def_blk_fops = {\nblock/fops.c-931-\t.open\t\t= blkdev_open,\n--\nblock/genhd.c=427=static int __add_disk(struct device *parent, struct gendisk *disk,\n--\nblock/genhd.c-441-\t\t */\nblock/genhd.c:442:\t\tif (disk-\u003efops-\u003esubmit_bio || disk-\u003efops-\u003epoll_bio)\nblock/genhd.c-443-\t\t\treturn -EINVAL;\nblock/genhd.c-444-\t} else {\nblock/genhd.c:445:\t\tif (!disk-\u003efops-\u003esubmit_bio)\nblock/genhd.c-446-\t\t\treturn -EINVAL;\n--\nblock/genhd.c=1280=static void disk_release(struct device *dev)\n--\nblock/genhd.c-1317-\nblock/genhd.c:1318:\tif (test_bit(GD_ADDED, \u0026disk-\u003estate) \u0026\u0026 disk-\u003efops-\u003efree_disk)\nblock/genhd.c:1319:\t\tdisk-\u003efops-\u003efree_disk(disk);\nblock/genhd.c-1320-\n--\nblock/genhd.c=1336=static char *block_devnode(const struct device *dev, umode_t *mode,\n--\nblock/genhd.c-1340-\nblock/genhd.c:1341:\tif (disk-\u003efops-\u003edevnode)\nblock/genhd.c:1342:\t\treturn disk-\u003efops-\u003edevnode(disk, mode);\nblock/genhd.c-1343-\treturn NULL;\n--\nblock/ioctl.c=301=int blkdev_compat_ptr_ioctl(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-305-\nblock/ioctl.c:306:\tif (disk-\u003efops-\u003eioctl)\nblock/ioctl.c:307:\t\treturn disk-\u003efops-\u003eioctl(bdev, mode, cmd,\nblock/ioctl.c-308-\t\t\t\t\t (unsigned long)compat_ptr(arg));\n--\nblock/ioctl.c=342=static int blkdev_pr_register(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-344-{\nblock/ioctl.c:345:\tconst struct pr_ops *ops = bdev-\u003ebd_disk-\u003efops-\u003epr_ops;\nblock/ioctl.c-346-\tstruct pr_registration reg;\n--\nblock/ioctl.c=360=static int blkdev_pr_reserve(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-362-{\nblock/ioctl.c:363:\tconst struct pr_ops *ops = bdev-\u003ebd_disk-\u003efops-\u003epr_ops;\nblock/ioctl.c-364-\tstruct pr_reservation rsv;\n--\nblock/ioctl.c=378=static int blkdev_pr_release(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-380-{\nblock/ioctl.c:381:\tconst struct pr_ops *ops = bdev-\u003ebd_disk-\u003efops-\u003epr_ops;\nblock/ioctl.c-382-\tstruct pr_reservation rsv;\n--\nblock/ioctl.c=396=static int blkdev_pr_preempt(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-398-{\nblock/ioctl.c:399:\tconst struct pr_ops *ops = bdev-\u003ebd_disk-\u003efops-\u003epr_ops;\nblock/ioctl.c-400-\tstruct pr_preempt p;\n--\nblock/ioctl.c=414=static int blkdev_pr_clear(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-416-{\nblock/ioctl.c:417:\tconst struct pr_ops *ops = bdev-\u003ebd_disk-\u003efops-\u003epr_ops;\nblock/ioctl.c-418-\tstruct pr_clear c;\n--\nblock/ioctl.c=432=static int blkdev_pr_read_keys(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-434-{\nblock/ioctl.c:435:\tconst struct pr_ops *ops = bdev-\u003ebd_disk-\u003efops-\u003epr_ops;\nblock/ioctl.c-436-\tstruct pr_keys *keys_info;\n--\nblock/ioctl.c=487=static int blkdev_pr_read_reservation(struct block_device *bdev,\n--\nblock/ioctl.c-489-{\nblock/ioctl.c:490:\tconst struct pr_ops *ops = bdev-\u003ebd_disk-\u003efops-\u003epr_ops;\nblock/ioctl.c-491-\tstruct pr_held_reservation rsv = {};\n--\nblock/ioctl.c=531=static int blkdev_roset(struct block_device *bdev, unsigned cmd,\n--\nblock/ioctl.c-540-\t\treturn -EFAULT;\nblock/ioctl.c:541:\tif (bdev-\u003ebd_disk-\u003efops-\u003eset_read_only) {\nblock/ioctl.c:542:\t\tret = bdev-\u003ebd_disk-\u003efops-\u003eset_read_only(bdev, n);\nblock/ioctl.c-543-\t\tif (ret)\n--\nblock/ioctl.c=553=static int blkdev_getgeo(struct block_device *bdev,\n--\nblock/ioctl.c-561-\t\treturn -EINVAL;\nblock/ioctl.c:562:\tif (!disk-\u003efops-\u003egetgeo)\nblock/ioctl.c-563-\t\treturn -ENOTTY;\n--\nblock/ioctl.c-570-\tgeo.start = get_start_sect(bdev);\nblock/ioctl.c:571:\tret = disk-\u003efops-\u003egetgeo(disk, \u0026geo);\nblock/ioctl.c-572-\tif (ret)\n--\nblock/ioctl.c=587=static int compat_hdio_getgeo(struct block_device *bdev,\n--\nblock/ioctl.c-595-\t\treturn -EINVAL;\nblock/ioctl.c:596:\tif (!disk-\u003efops-\u003egetgeo)\nblock/ioctl.c-597-\t\treturn -ENOTTY;\n--\nblock/ioctl.c-604-\tgeo.start = get_start_sect(bdev);\nblock/ioctl.c:605:\tret = disk-\u003efops-\u003egetgeo(disk, \u0026geo);\nblock/ioctl.c-606-\tif (ret)\n--\nblock/ioctl.c=750=long blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)\n--\nblock/ioctl.c-795-\nblock/ioctl.c:796:\tif (!bdev-\u003ebd_disk-\u003efops-\u003eioctl)\nblock/ioctl.c-797-\t\treturn -ENOTTY;\nblock/ioctl.c:798:\treturn bdev-\u003ebd_disk-\u003efops-\u003eioctl(bdev, mode, cmd, arg);\nblock/ioctl.c-799-}\n--\nblock/ioctl.c=810=long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)\n--\nblock/ioctl.c-852-\tret = blkdev_common_ioctl(bdev, mode, cmd, arg, argp);\nblock/ioctl.c:853:\tif (ret == -ENOIOCTLCMD \u0026\u0026 disk-\u003efops-\u003ecompat_ioctl)\nblock/ioctl.c:854:\t\tret = disk-\u003efops-\u003ecompat_ioctl(bdev, mode, cmd, arg);\nblock/ioctl.c-855-\n--\nblock/partitions/core.c=518=static bool disk_unlock_native_capacity(struct gendisk *disk)\nblock/partitions/core.c-519-{\nblock/partitions/core.c:520:\tif (!disk-\u003efops-\u003eunlock_native_capacity ||\nblock/partitions/core.c-521-\t    test_and_set_bit(GD_NATIVE_CAPACITY, \u0026disk-\u003estate)) {\n--\nblock/partitions/core.c-526-\tprintk(KERN_CONT \"enabling native capacity\\n\");\nblock/partitions/core.c:527:\tdisk-\u003efops-\u003eunlock_native_capacity(disk);\nblock/partitions/core.c-528-\treturn true;\n--\nblock/partitions/efi.c=580=static int find_valid_gpt(struct parsed_partitions *state, gpt_header **gpt,\n--\nblock/partitions/efi.c-587-\tstruct gendisk *disk = state-\u003edisk;\nblock/partitions/efi.c:588:\tconst struct block_device_operations *fops = disk-\u003efops;\nblock/partitions/efi.c-589-\tsector_t total_sectors = get_capacity(state-\u003edisk);\n--\nblock/partitions/efi.c-622-\nblock/partitions/efi.c:623:\tif (!good_agpt \u0026\u0026 force_gpt \u0026\u0026 fops-\u003ealternative_gpt_sector) {\nblock/partitions/efi.c-624-\t\tsector_t agpt_sector;\n--\nblock/partitions/efi.c-626-\nblock/partitions/efi.c:627:\t\terr = fops-\u003ealternative_gpt_sector(disk, \u0026agpt_sector);\nblock/partitions/efi.c-628-\t\tif (!err)\n--\nblock/partitions/ibm.c=318=int ibm_partition(struct parsed_partitions *state)\n--\nblock/partitions/ibm.c-333-\tres = 0;\nblock/partitions/ibm.c:334:\tif (!disk-\u003efops-\u003egetgeo)\nblock/partitions/ibm.c-335-\t\tgoto out_exit;\n--\nblock/partitions/ibm.c-353-\tgeo-\u003estart = get_start_sect(bdev);\nblock/partitions/ibm.c:354:\tif (disk-\u003efops-\u003egetgeo(disk, geo))\nblock/partitions/ibm.c-355-\t\tgoto out_freeall;\n"
}

gemini-3.8-flash

null

null

							input: 14230
							output: 24
							thoughts: 62
						

Here's my summary, as though I'm thinking through this process:

**Diving into the Block Layer Build System**

Okay, so I'm looking at the `block/Makefile` and immediately see the `obj-y` assignment. Right, these are the object files that are going to be compiled into the block device driver. I spot `bdev.o`, `fops.o`, `bio.o`, `elevator.o`, `blk-core.o`, `blk-sysfs.o`... a comprehensive list, seems like. Now, before I go any further, I want to make sure I understand the conditional compilation. I'm going to quickly check `block/Kconfig` – I bet the inclusion of this whole block layer is controlled by a `BLOCK` config option. I need to make sure this is enabled so I don't waste time tracing the code if it is not compiled in.

{
  "Expression": "config BLOCK",
  "PathPrefix": "block/"
}

{
  "Output": "block/Kconfig-4-#\nblock/Kconfig:5:menuconfig BLOCK\nblock/Kconfig-6-       bool \"Enable the block layer\" if EXPERT\n--\nblock/Kconfig=27=if BLOCK\nblock/Kconfig-28-\nblock/Kconfig:29:config BLOCK_LEGACY_AUTOLOAD\nblock/Kconfig-30-\tbool \"Legacy autoloading support\"\n--\nblock/Kconfig=214=config BLK_PM\n--\nblock/Kconfig-217-# do not use in new code\nblock/Kconfig:218:config BLOCK_HOLDER_DEPRECATED\nblock/Kconfig-219-\tbool\n"
}

gemini-3.8-flash

null

null

							input: 14686
							output: 29
							thoughts: 799
						

**Analyzing `BLKDEV_ZERO_KILLABLE` and `fallocate` in the Block Layer**

Okay, so I'm thinking about how `BLOCK` enables the block layer, and I'm also considering how `BLKDEV_ZERO_KILLABLE` and the `fallocate` system call relate to that.  I want to understand the specifics.  My first instinct is to zero in on `BLKDEV_ZERO_KILLABLE` to understand its behavior. Let's start with `block/fops.c` and how `blkdev_fallocate` is implemented there.  I see it's the `fallocate` method of `def_blk_fops`.

```c
const struct file_operations def_blk_fops = {
	...
	.fallocate	= blkdev_fallocate,
	...
};
```

That's the entry point. Next, I want to confirm how `BLKDEV_ZERO_KILLABLE` is defined. I'll look into `include/linux/blkdev.h`. And there it is: it's a simple macro definition.

```c
#define BLKDEV_ZERO_KILLABLE	(1 << 2)  /* interruptible by fatal signals */
```

Excellent. No conditional compilation based on other configuration options. `BLKDEV_ZERO_KILLABLE` is available if the block layer is enabled.  And, oh yeah, `BLOCK` is the config flag. It's a fundamental part of the configuration. So, with the block layer enabled, this feature is available.

Now I need to refine my focus. I'm going to look at the symbols that are involved in this code path. So based on what I have seen, the functions that are modified are `blkdev_fallocate`. And the functions directly involved in handling `BLKDEV_ZERO_KILLABLE` are `blkdev_fallocate`, `blkdev_issue_zeroout`, `__blkdev_issue_write_zeroes`, `__blkdev_issue_zero_pages`, and `bio_submit_or_kill`.

Let me think. I know `blkdev_fallocate` is declared as a static function in `block/fops.c`. But since its address is taken (`.fallocate = blkdev_fallocate,`) in the `file_operations` structure, the compiler MUST generate an out-of-line function for it, and therefore it *will* have a symbol in vmlinux. Good, I can trace it. What about `blkdev_issue_zeroout`? That's going to be in `block/blk-lib.c`. I will have to look at `block/blk-lib.c`.

{
  "Expression": "blkdev_issue_zeroout",
  "PathPrefix": "block/"
}

{
  "Output": "block/blk-lib.c=220=static int blkdev_issue_zero_pages(struct block_device *bdev, sector_t sector,\n--\nblock/blk-lib.c-241-/**\nblock/blk-lib.c:242: * __blkdev_issue_zeroout - generate number of zero filed write bios\nblock/blk-lib.c-243- * @bdev:\tblockdev to issue\n--\nblock/blk-lib.c-259- */\nblock/blk-lib.c:260:int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,\nblock/blk-lib.c-261-\t\tsector_t nr_sects, gfp_t gfp_mask, struct bio **biop,\n--\nblock/blk-lib.c-279-}\nblock/blk-lib.c:280:EXPORT_SYMBOL(__blkdev_issue_zeroout);\nblock/blk-lib.c-281-\nblock/blk-lib.c-282-/**\nblock/blk-lib.c:283: * blkdev_issue_zeroout - zero-fill a block range\nblock/blk-lib.c-284- * @bdev:\tblockdev to write\n--\nblock/blk-lib.c-291- *  Zero-fill a block range, either using hardware offload or by explicitly\nblock/blk-lib.c:292: *  writing zeroes to the device.  See __blkdev_issue_zeroout() for the\nblock/blk-lib.c-293- *  valid values for %flags.\nblock/blk-lib.c-294- */\nblock/blk-lib.c:295:int blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,\nblock/blk-lib.c-296-\t\tsector_t nr_sects, gfp_t gfp_mask, unsigned flags)\n--\nblock/blk-lib.c-313-}\nblock/blk-lib.c:314:EXPORT_SYMBOL(blkdev_issue_zeroout);\nblock/blk-lib.c-315-\n--\nblock/blk-zoned.c=2391=EXPORT_SYMBOL_GPL(blk_revalidate_disk_zones);\n--\nblock/blk-zoned.c-2402- *  pointer), handling potential errors due to the (initially unknown) lack of\nblock/blk-zoned.c:2403: *  hardware offload (See blkdev_issue_zeroout()).\nblock/blk-zoned.c-2404- */\nblock/blk-zoned.c=2405=int blk_zone_issue_zeroout(struct block_device *bdev, sector_t sector,\n--\nblock/blk-zoned.c-2413-\nblock/blk-zoned.c:2414:\tret = blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask,\nblock/blk-zoned.c-2415-\t\t\t\t   BLKDEV_ZERO_NOFALLBACK);\n--\nblock/blk-zoned.c-2419-\t/*\nblock/blk-zoned.c:2420:\t * The failed call to blkdev_issue_zeroout() advanced the zone write\nblock/blk-zoned.c-2421-\t * pointer. Undo this using a report zone to update the zone write\n--\nblock/blk-zoned.c-2431-\t */\nblock/blk-zoned.c:2432:\treturn blkdev_issue_zeroout(bdev, sector, nr_sects, gfp_mask, 0);\nblock/blk-zoned.c-2433-}\n--\nblock/fops.c=845=static long blkdev_fallocate(struct file *file, int mode, loff_t start,\n--\nblock/fops.c-910-\nblock/fops.c:911:\terror = blkdev_issue_zeroout(bdev, start \u003e\u003e SECTOR_SHIFT,\nblock/fops.c-912-\t\t\t\t     len \u003e\u003e SECTOR_SHIFT, GFP_KERNEL,\n--\nblock/ioctl.c=211=static int blk_ioctl_zeroout(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-243-\nblock/ioctl.c:244:\terr = blkdev_issue_zeroout(bdev, start \u003e\u003e 9, len \u003e\u003e 9, GFP_KERNEL,\nblock/ioctl.c-245-\t\t\t\t   BLKDEV_ZERO_NOUNMAP | BLKDEV_ZERO_KILLABLE);\n"
}

gemini-3.8-flash

null

null

							input: 17266
							output: 29
							thoughts: 58
						

Okay, here's my interpretation of these thoughts, formatted as you requested:

**Navigating Block Device Interaction**

Alright, so `blkdev_issue_zeroout` is an exported symbol, which means it's designed to be used externally, that's good to know. Now, I see `bio_submit_or_kill` is also exported, and it resides in `block/bio.c`.  That's my starting point. I need to understand *how* it's implemented. I'm going to dig into the source code for that function within `block/bio.c` to understand its operation and how it interfaces with the lower layers. I want to see how these exported symbols interact to ensure proper block device handling. I need to see what `bio_submit_or_kill` actually does in relation to the bio structure itself, as well as the 'kill' aspect of the function.

{
  "Expression": "bio_submit_or_kill",
  "PathPrefix": "block/"
}

{
  "Output": "block/bio.c=1604=static void bio_endio_cb(struct bio *bio, void *priv)\n--\nblock/bio.c-1612- */\nblock/bio.c:1613:int bio_submit_or_kill(struct bio *bio, unsigned int flags)\nblock/bio.c-1614-{\n--\nblock/blk-lib.c=146=static int blkdev_issue_write_zeroes(struct block_device *bdev, sector_t sector,\n--\nblock/blk-lib.c-157-\tif (bio) {\nblock/blk-lib.c:158:\t\tret = bio_submit_or_kill(bio, flags);\nblock/blk-lib.c-159-\t\tbio_put(bio);\n--\nblock/blk-lib.c=220=static int blkdev_issue_zero_pages(struct block_device *bdev, sector_t sector,\n--\nblock/blk-lib.c-232-\tif (bio) {\nblock/blk-lib.c:233:\t\tret = bio_submit_or_kill(bio, flags);\nblock/blk-lib.c-234-\t\tbio_put(bio);\n--\nblock/blk.h=63=void submit_bio_noacct_nocheck(struct bio *bio, bool split);\nblock/blk.h:64:int bio_submit_or_kill(struct bio *bio, unsigned int flags);\nblock/blk.h-65-\n--\nblock/ioctl.c=122=static int blk_ioctl_discard(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-164-\tif (prev) {\nblock/ioctl.c:165:\t\terr = bio_submit_or_kill(prev, BLKDEV_ZERO_KILLABLE);\nblock/ioctl.c-166-\t\tif (err == -EOPNOTSUPP)\n"
}

gemini-3.8-flash

null

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							input: 18049
							output: 129
							thoughts: 746
						

**Analysis of the Block Device Fallocate Patch for Fuzzing**

Okay, let's break this down. My initial hunch about `bio_submit_or_kill`, `blkdev_fallocate`, and `blkdev_issue_zeroout` seems correct as relevant FocusSymbols, but they aren't as ubiquitous as I initially thought. They are, however, critical entrypoints and implementation details for a specific feature. This patch directly modifies `blkdev_fallocate` within `block/fops.c`, and that's the key. This makes sense; `fallocate` is the syscall we want to focus on here, particularly on block devices.

The call chain is clear: `blkdev_fallocate` is called by the `fallocate` syscall, and now it sets the `BLKDEV_ZERO_KILLABLE` flag when submitting zeroout requests through `blkdev_issue_zeroout`. This, in turn, influences behavior inside `bio_submit_or_kill`, specifically how zeroing operations are handled when a fatal signal like SIGKILL is pending. My main concern is that the original error handling, and any loops that might get interrupted, will need to be reevaluated. This potentially introduces race conditions, resource leaks, or subtle error handling problems, particularly in the block layer and bio submission paths.

Let's verify the configuration dependencies. `block/fops.c` definitely relies on `CONFIG_BLOCK`, and there are no conditional compilation blocks around the modified code. Good, that simplifies things. `CONFIG_BLOCK` is sufficient for this.

Now, does this meet the criteria for "WorthFuzzing"? Absolutely. The patch clearly modifies reachable, executable code in `blkdev_fallocate()`. It touches the block layer, and, importantly, it changes error handling and loop behavior. The addition of `BLKDEV_ZERO_KILLABLE` on the zeroout path, which makes the zeroing operation abortable, is a significant change. Furthermore, syzkaller has the perfect setup to hit this scenario. We can leverage block device fuzzing, which is already working, and we know that syzkaller frequently injects signals, precisely the kind of events that trigger the new conditional behavior.

Therefore, my conclusions are:

*   **WorthFuzzing:** `true`
*   **Reasoning:** The patch introduces a change in the fallocate implementation where zero-out operations are now abortable upon fatal signals through the newly introduced `BLKDEV_ZERO_KILLABLE` flag. This modification can lead to new edge cases and race conditions by altering error handling, loop behavior and bio submission flows in block devices. This code path is easily reachable from user-space via the `fallocate()` syscall.
*   **EnableConfigs:** `["BLOCK"]`
*   **FocusSymbols:** `["blkdev_fallocate", "blkdev_issue_zeroout", "bio_submit_or_kill"]`

I'm confident in these findings. Let's call `set-results`.

{
  "EnableConfigs": [
    "BLOCK"
  ],
  "FocusSymbols": [
    "blkdev_fallocate",
    "blkdev_issue_zeroout",
    "bio_submit_or_kill"
  ],
  "Reasoning": "The patch modifies blkdev_fallocate() to include the BLKDEV_ZERO_KILLABLE flag when issuing zeroouts on block devices. This alters control flow and bio submission handling when fatal signals are pending, making the operation interruptible. This affects reachable core block layer functionality exerciseable via the fallocate syscall on block devices.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "BLOCK"
  ],
  "FocusSymbols": [
    "blkdev_fallocate",
    "blkdev_issue_zeroout",
    "bio_submit_or_kill"
  ],
  "Reasoning": "The patch modifies blkdev_fallocate() to include the BLKDEV_ZERO_KILLABLE flag when issuing zeroouts on block devices. This alters control flow and bio submission handling when fatal signals are pending, making the operation interruptible. This affects reachable core block layer functionality exerciseable via the fallocate syscall on block devices.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

core

null

{
  "KMSANReasoning": "The patch modifies `blkdev_fallocate` in `block/fops.c` to include the `BLKDEV_ZERO_KILLABLE` flag when calling `blkdev_issue_zeroout()`. This allows zeroing operations on block devices to be interrupted by fatal signals.\n\nThe modification only alters an integer flags parameter passed into an existing function. It does not introduce, allocate, or modify any buffers, structures, padding, or data copied to userspace, nor does it affect any bounds checks or logic dealing with uninitialized memory. Therefore, there is no risk of uninitialized memory reads or info-leaks, and a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}

You are an expert Linux kernel security engineer specializing in kernel memory
error detectors (KASAN and KMSAN). Your job is to review the provided patch series and
determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer)
fuzzing session in addition to standard KASAN fuzzing.

CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN:
- Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable
  a comprehensive suite of debugging tools and sanitizers, including KASAN
  (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP
  (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks.
- KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap,
  or page allocations) and kernel-to-user memory info-leaks.

Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN,
LOCKDEP, OR OTHER STANDARD BUG DETECTORS.
A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY
set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks
that are detected ONLY by KMSAN.

Look holistically at the patch series and surrounding code. Even if no direct
uninitialized field accesses or new buffer allocations are added in the diff itself,
a patch may alter control flow, bounds checking, or data length calculations in ways
that change how the rest of the code operates on existing buffers (e.g. allowing
uninitialized stack/heap memory to be read, copied to user space, or used in control
flow). Do not hesitate to use your code access tools to inspect the surrounding code,
called functions, and callers.

Set NeedsKMSAN=true ONLY IF the patch introduces or modifies:
1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb
   attributes, ioctl output arguments, socket options, or BPF buffers) where fields
   or structure padding might not be fully initialized/zeroed.
2. Conditional logic or branching that depends on potentially uninitialized variables
   or struct fields.
3. Allocation or initialization of complex data structures where uninitialized fields
   could be read later in reachable code paths.
4. Bounds checks, lengths, or logic in a way that allows surrounding code to access
   uninitialized bytes of existing buffers.

Set NeedsKMSAN=false IF:
- The code changes primarily risk out-of-bounds access, array overflows, NULL pointer
  dereferences, locking deadlocks, or use-after-free bugs (these are already caught
  by KASAN, LOCKDEP, or standard bug detectors).
- All stack/heap structures touched or introduced by the patch are fully zeroed
  or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied.
- The patch does not introduce any risk of uninitialized memory usage or info-leaks.

Use your code access tools to inspect the surrounding code if necessary, then provide
detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch.
Prefer calling several tools at the same time to save round-trips.


Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Target architecture: amd64

For your convenience, here is the diff of the changes:
commit ee9c5db58bfed74ccd756b49c26190ff92f6a18f
Author: syz-cluster <triage@syzkaller.com>
Date:   Mon Sep 28 10:59:23 2026 +0000

    syz-cluster: applied patch under review

diff --git a/block/fops.c b/block/fops.c
index 2ce7c6c4714e4..a2fe27d8ceff1 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -909,7 +909,8 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 		goto fail;
 
 	error = blkdev_issue_zeroout(bdev, start >> SECTOR_SHIFT,
-				     len >> SECTOR_SHIFT, GFP_KERNEL, flags);
+				     len >> SECTOR_SHIFT, GFP_KERNEL,
+				     flags | BLKDEV_ZERO_KILLABLE);
  fail:
 	filemap_invalidate_unlock(inode->i_mapping);
 	inode_unlock(inode);

gemini-3.8-flash

null

null

							input: 2088
							output: 34
							thoughts: 297
						

**Evaluating the KMSAN Fuzzing Necessity**

Okay, so I need to decide if this patch series warrants spinning up a dedicated KMSAN fuzzing session. Let's dig in. Looking at the diff, it seems to be in `block/fops.c`. Specifically, it appears to be a modification within the `blkdev_fallocate` function. It looks like the addition is the `BLKDEV_ZERO_KILLABLE` flag.

My immediate thought is, let's look at the surrounding code within `block/fops.c`, specifically around line 909, to fully understand the context. I need to know what `blkdev_fallocate` does, and critically, how this new `BLKDEV_ZERO_KILLABLE` flag alters the behavior of `blkdev_issue_zeroout`. This context will be crucial in deciding if this change introduces a potential KMSAN-specific vulnerability or interesting execution path that fuzzing should explore. I'll need to figure out if this flag could lead to memory corruption or other issues under certain conditions that fuzzing might reveal.

{
  "File": "block/fops.c",
  "FirstLine": 870,
  "LineCount": 60
}

{
  "Contents": " 870:\t\tif (end \u003e= isize) {\n 871:\t\t\tif (mode \u0026 FALLOC_FL_KEEP_SIZE) {\n 872:\t\t\t\tlen = isize - start;\n 873:\t\t\t\tend = start + len - 1;\n 874:\t\t\t} else\n 875:\t\t\t\treturn -EINVAL;\n 876:\t\t}\n 877:\t\n 878:\t\t/*\n 879:\t\t * Don't allow IO that isn't aligned to logical block size.\n 880:\t\t */\n 881:\t\tif ((start | len) \u0026 (bdev_logical_block_size(bdev) - 1))\n 882:\t\t\treturn -EINVAL;\n 883:\t\n 884:\t\tinode_lock(inode);\n 885:\t\tfilemap_invalidate_lock(inode-\u003ei_mapping);\n 886:\t\n 887:\t\tswitch (mode) {\n 888:\t\tcase FALLOC_FL_ZERO_RANGE:\n 889:\t\tcase FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE:\n 890:\t\t\tflags = BLKDEV_ZERO_NOUNMAP;\n 891:\t\t\tbreak;\n 892:\t\tcase FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:\n 893:\t\t\tflags = BLKDEV_ZERO_NOFALLBACK;\n 894:\t\t\tbreak;\n 895:\t\tcase FALLOC_FL_WRITE_ZEROES:\n 896:\t\t\tflags = 0;\n 897:\t\t\tbreak;\n 898:\t\tdefault:\n 899:\t\t\terror = -EOPNOTSUPP;\n 900:\t\t\tgoto fail;\n 901:\t\t}\n 902:\t\n 903:\t\t/*\n 904:\t\t * Invalidate the page cache, including dirty pages, for valid\n 905:\t\t * de-allocate mode calls to fallocate().\n 906:\t\t */\n 907:\t\terror = truncate_bdev_range(bdev, file_to_blk_mode(file), start, end);\n 908:\t\tif (error)\n 909:\t\t\tgoto fail;\n 910:\t\n 911:\t\terror = blkdev_issue_zeroout(bdev, start \u003e\u003e SECTOR_SHIFT,\n 912:\t\t\t\t\t     len \u003e\u003e SECTOR_SHIFT, GFP_KERNEL,\n 913:\t\t\t\t\t     flags | BLKDEV_ZERO_KILLABLE);\n 914:\t fail:\n 915:\t\tfilemap_invalidate_unlock(inode-\u003ei_mapping);\n 916:\t\tinode_unlock(inode);\n 917:\t\treturn error;\n 918:\t}\n 919:\t\n 920:\tstatic int blkdev_mmap_prepare(struct vm_area_desc *desc)\n 921:\t{\n 922:\t\tstruct file *file = desc-\u003efile;\n 923:\t\n 924:\t\tif (bdev_read_only(I_BDEV(bdev_file_inode(file))))\n 925:\t\t\treturn generic_file_readonly_mmap_prepare(desc);\n 926:\t\n 927:\t\treturn generic_file_mmap_prepare(desc);\n 928:\t}\n 929:\t\n"
}

gemini-3.8-flash

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							input: 3517
							output: 21
							thoughts: 25
						

Okay, here's my summary, presented as a stream of thought:

**Diving into `BLKDEV_ZERO_KILLABLE` and `blkdev_issue_zeroout`**

Alright, let's get down to brass tacks. I'm taking a look at how `BLKDEV_ZERO_KILLABLE` actually functions within the context of `blkdev_issue_zeroout`. I know the overall goal here: the kernel is trying to efficiently zero out a block device. Now I need to understand the specifics of how `BLKDEV_ZERO_KILLABLE` influences that zeroing process. Is it a *control* parameter? A *flag*? I need to figure out exactly how it interfaces with the lower levels of the block device stack. Is it about allowing the zeroing operation to be killed if it's taking too long? Or is it something more subtle, perhaps related to error handling or resource allocation during the zeroing? My intuition says it must be important to error handling or to make sure the process can terminate, but I need to see the code to understand the semantics. Time to trace the execution path and see what's what. The finer points of this will impact how the process deals with potentially unreliable or slower-than-expected storage. Let's see how the kernel deals with that.

{
  "Expression": "BLKDEV_ZERO_KILLABLE"
}

{
  "Output": "block/bio.c=1613=int bio_submit_or_kill(struct bio *bio, unsigned int flags)\nblock/bio.c-1614-{\nblock/bio.c:1615:\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026 fatal_signal_pending(current)) {\nblock/bio.c-1616-\t\tbio_await(bio, NULL, bio_endio_cb);\n--\nblock/blk-lib.c=119=static void __blkdev_issue_write_zeroes(struct block_device *bdev,\n--\nblock/blk-lib.c-127-\nblock/blk-lib.c:128:\t\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026\nblock/blk-lib.c-129-\t\t    fatal_signal_pending(current))\n--\nblock/blk-lib.c=187=static void __blkdev_issue_zero_pages(struct block_device *bdev,\n--\nblock/blk-lib.c-196-\nblock/blk-lib.c:197:\t\tif ((flags \u0026 BLKDEV_ZERO_KILLABLE) \u0026\u0026\nblock/blk-lib.c-198-\t\t    fatal_signal_pending(current))\n--\nblock/fops.c=845=static long blkdev_fallocate(struct file *file, int mode, loff_t start,\n--\nblock/fops.c-912-\t\t\t\t     len \u003e\u003e SECTOR_SHIFT, GFP_KERNEL,\nblock/fops.c:913:\t\t\t\t     flags | BLKDEV_ZERO_KILLABLE);\nblock/fops.c-914- fail:\n--\nblock/ioctl.c=122=static int blk_ioctl_discard(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-164-\tif (prev) {\nblock/ioctl.c:165:\t\terr = bio_submit_or_kill(prev, BLKDEV_ZERO_KILLABLE);\nblock/ioctl.c-166-\t\tif (err == -EOPNOTSUPP)\n--\nblock/ioctl.c=211=static int blk_ioctl_zeroout(struct block_device *bdev, blk_mode_t mode,\n--\nblock/ioctl.c-244-\terr = blkdev_issue_zeroout(bdev, start \u003e\u003e 9, len \u003e\u003e 9, GFP_KERNEL,\nblock/ioctl.c:245:\t\t\t\t   BLKDEV_ZERO_NOUNMAP | BLKDEV_ZERO_KILLABLE);\nblock/ioctl.c-246-\n--\ninclude/linux/blkdev.h=1191=int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector,\n--\ninclude/linux/blkdev.h-1195-#define BLKDEV_ZERO_NOFALLBACK\t(1 \u003c\u003c 1)  /* don't write explicit zeroes */\ninclude/linux/blkdev.h:1196:#define BLKDEV_ZERO_KILLABLE\t(1 \u003c\u003c 2)  /* interruptible by fatal signals */\ninclude/linux/blkdev.h-1197-\n"
}

gemini-3.8-flash

null

null

							input: 4636
							output: 167
							thoughts: 515
						

**KMSAN Considerations for the Block Device Zeroout Patch**

Okay, so this patch is straightforward: it's just adding `BLKDEV_ZERO_KILLABLE` to the `blkdev_issue_zeroout` call within `blkdev_fallocate`. This is essentially enabling signal interruption for zeroout operations, mirroring the behavior of `blk_ioctl_zeroout()`.

Now, the question is, does this introduce a KMSAN risk? I need to meticulously check against the rules. Let's see... the rules are pretty clear: does the change introduce or modify kernel data structures sent to userspace, rely on uninitialized variables, involve complex data structure allocation with potential uninitialized reads, or affect bounds checks in a way that risks exposing uninitialized memory? No, no, and no.

*   This patch *only* modifies a flag passed to a function.
*   No new memory allocation. No copying to userspace. No uninitialized variables left hanging around. No alterations to buffer bounds.

The primary risks here would be signal-handling logic bugs (state inconsistency, locking, refcounting, resource leaks), but those are logic flaws, resource leaks, or handled by KASAN, LOCKDEP or other standard detection tools. There's absolutely *zero* risk of uninitialized memory *reads* or information leaks introduced by this patch.

Therefore, `NeedsKMSAN` is definitively `false`. Time to write a clear `KMSANReasoning` explanation, clearly contrasting KASAN and KMSAN.

{
  "KMSANReasoning": "The patch modifies `blkdev_fallocate` in `block/fops.c` to include the `BLKDEV_ZERO_KILLABLE` flag when calling `blkdev_issue_zeroout()`. This allows zeroing operations on block devices to be interrupted by fatal signals.\n\nThe modification only alters an integer flags parameter passed into an existing function. It does not introduce, allocate, or modify any buffers, structures, padding, or data copied to userspace, nor does it affect any bounds checks or logic dealing with uninitialized memory. Therefore, there is no risk of uninitialized memory reads or info-leaks, and a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch modifies `blkdev_fallocate` in `block/fops.c` to include the `BLKDEV_ZERO_KILLABLE` flag when calling `blkdev_issue_zeroout()`. This allows zeroing operations on block devices to be interrupted by fatal signals.\n\nThe modification only alters an integer flags parameter passed into an existing function. It does not introduce, allocate, or modify any buffers, structures, padding, or data copied to userspace, nor does it affect any bounds checks or logic dealing with uninitialized memory. Therefore, there is no risk of uninitialized memory reads or info-leaks, and a dedicated KMSAN fuzzing session is not warranted.",
  "NeedsKMSAN": false
}