AI Trajectory

null

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_fill_write_pages",
    "fuse_notify_store",
    "iomap_folio_mark_uptodate"
  ],
  "Reasoning": "The patch modifies page uptodate handling in FUSE write and notify paths, and introduces a new iomap helper. These are functional changes in filesystem logic that can be triggered by user-space via FUSE.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit f51937a5457a7f1a589c1f897d2000044299a84d\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Jul 8 08:47:16 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/fs/fuse/file.c b/fs/fuse/file.c\nindex ceada75310b880..da5859e8159d4f 100644\n--- a/fs/fuse/file.c\n+++ b/fs/fuse/file.c\n@@ -1219,8 +1219,7 @@ static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,\n \tstruct file *file = iocb-\u003eki_filp;\n \tstruct fuse_file *ff = file-\u003eprivate_data;\n \tstruct fuse_mount *fm = ff-\u003efm;\n-\tunsigned int offset, i;\n-\tbool short_write;\n+\tunsigned int i;\n \tint err;\n \n \tfor (i = 0; i \u003c ap-\u003enum_folios; i++)\n@@ -1235,24 +1234,9 @@ static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,\n \tif (!err \u0026\u0026 ia-\u003ewrite.out.size \u003e count)\n \t\terr = -EIO;\n \n-\tshort_write = ia-\u003ewrite.out.size \u003c count;\n-\toffset = ap-\u003edescs[0].offset;\n-\tcount = ia-\u003ewrite.out.size;\n \tfor (i = 0; i \u003c ap-\u003enum_folios; i++) {\n \t\tstruct folio *folio = ap-\u003efolios[i];\n \n-\t\tif (err) {\n-\t\t\tfolio_clear_uptodate(folio);\n-\t\t} else {\n-\t\t\tif (count \u003e= folio_size(folio) - offset)\n-\t\t\t\tcount -= folio_size(folio) - offset;\n-\t\t\telse {\n-\t\t\t\tif (short_write)\n-\t\t\t\t\tfolio_clear_uptodate(folio);\n-\t\t\t\tcount = 0;\n-\t\t\t}\n-\t\t\toffset = 0;\n-\t\t}\n \t\tif (ia-\u003ewrite.folio_locked \u0026\u0026 (i == ap-\u003enum_folios - 1))\n \t\t\tfolio_unlock(folio);\n \t\tfolio_put(folio);\n@@ -1327,7 +1311,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,\n \n \t\t/* If we copied full folio, mark it uptodate */\n \t\tif (tmp == folio_size(folio))\n-\t\t\tfolio_mark_uptodate(folio);\n+\t\t\tiomap_folio_mark_uptodate(folio);\n \n \t\tif (folio_test_uptodate(folio)) {\n \t\t\tfolio_unlock(folio);\ndiff --git a/fs/fuse/notify.c b/fs/fuse/notify.c\nindex 29578104ae6cd6..1ba763705d9119 100644\n--- a/fs/fuse/notify.c\n+++ b/fs/fuse/notify.c\n@@ -2,6 +2,8 @@\n \n #include \"dev.h\"\n #include \"fuse_i.h\"\n+\n+#include \u003clinux/iomap.h\u003e\n #include \u003clinux/pagemap.h\u003e\n \n static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,\n@@ -192,7 +194,7 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,\n \t\tif (!folio_test_uptodate(folio) \u0026\u0026 !err \u0026\u0026 folio_offset == 0 \u0026\u0026\n \t\t    (nr_bytes == folio_size(folio) || file_size == end)) {\n \t\t\tfolio_zero_segment(folio, nr_bytes, folio_size(folio));\n-\t\t\tfolio_mark_uptodate(folio);\n+\t\t\tiomap_folio_mark_uptodate(folio);\n \t\t}\n \t\tfolio_unlock(folio);\n \t\tfolio_put(folio);\ndiff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c\nindex 276720bc18dc52..af415293e2651f 100644\n--- a/fs/iomap/buffered-io.c\n+++ b/fs/iomap/buffered-io.c\n@@ -105,6 +105,12 @@ static void iomap_set_range_uptodate(struct folio *folio, size_t off,\n \t\tfolio_mark_uptodate(folio);\n }\n \n+void iomap_folio_mark_uptodate(struct folio *folio)\n+{\n+\tiomap_set_range_uptodate(folio, 0, folio_size(folio));\n+}\n+EXPORT_SYMBOL_GPL(iomap_folio_mark_uptodate);\n+\n /*\n  * Find the next dirty block in the folio. end_blk is inclusive.\n  * If no dirty block is found, this will return end_blk + 1.\ndiff --git a/include/linux/iomap.h b/include/linux/iomap.h\nindex 56b43d594e6e29..40aa3476a351d2 100644\n--- a/include/linux/iomap.h\n+++ b/include/linux/iomap.h\n@@ -365,6 +365,7 @@ struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len);\n bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags);\n void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len);\n bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio);\n+void iomap_folio_mark_uptodate(struct folio *folio);\n int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,\n \t\tconst struct iomap_ops *ops,\n \t\tconst struct iomap_write_ops *write_ops);\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_fill_write_pages",
    "fuse_notify_store",
    "iomap_folio_mark_uptodate"
  ],
  "Reasoning": "The patch modifies page uptodate handling in FUSE write and notify paths, and introduces a new iomap helper. These are functional changes in filesystem logic that can be triggered by user-space via FUSE.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. List them in the EnableConfigs output array,
   and DO NOT add a '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.

For your convenience, here is the diff of the changes:
commit f51937a5457a7f1a589c1f897d2000044299a84d
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Jul 8 08:47:16 2026 +0000

    syz-cluster: applied patch under review

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index ceada75310b880..da5859e8159d4f 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1219,8 +1219,7 @@ static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,
 	struct file *file = iocb->ki_filp;
 	struct fuse_file *ff = file->private_data;
 	struct fuse_mount *fm = ff->fm;
-	unsigned int offset, i;
-	bool short_write;
+	unsigned int i;
 	int err;
 
 	for (i = 0; i < ap->num_folios; i++)
@@ -1235,24 +1234,9 @@ static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,
 	if (!err && ia->write.out.size > count)
 		err = -EIO;
 
-	short_write = ia->write.out.size < count;
-	offset = ap->descs[0].offset;
-	count = ia->write.out.size;
 	for (i = 0; i < ap->num_folios; i++) {
 		struct folio *folio = ap->folios[i];
 
-		if (err) {
-			folio_clear_uptodate(folio);
-		} else {
-			if (count >= folio_size(folio) - offset)
-				count -= folio_size(folio) - offset;
-			else {
-				if (short_write)
-					folio_clear_uptodate(folio);
-				count = 0;
-			}
-			offset = 0;
-		}
 		if (ia->write.folio_locked && (i == ap->num_folios - 1))
 			folio_unlock(folio);
 		folio_put(folio);
@@ -1327,7 +1311,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 
 		/* If we copied full folio, mark it uptodate */
 		if (tmp == folio_size(folio))
-			folio_mark_uptodate(folio);
+			iomap_folio_mark_uptodate(folio);
 
 		if (folio_test_uptodate(folio)) {
 			folio_unlock(folio);
diff --git a/fs/fuse/notify.c b/fs/fuse/notify.c
index 29578104ae6cd6..1ba763705d9119 100644
--- a/fs/fuse/notify.c
+++ b/fs/fuse/notify.c
@@ -2,6 +2,8 @@
 
 #include "dev.h"
 #include "fuse_i.h"
+
+#include <linux/iomap.h>
 #include <linux/pagemap.h>
 
 static int fuse_notify_poll(struct fuse_conn *fc, unsigned int size,
@@ -192,7 +194,7 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
 		if (!folio_test_uptodate(folio) && !err && folio_offset == 0 &&
 		    (nr_bytes == folio_size(folio) || file_size == end)) {
 			folio_zero_segment(folio, nr_bytes, folio_size(folio));
-			folio_mark_uptodate(folio);
+			iomap_folio_mark_uptodate(folio);
 		}
 		folio_unlock(folio);
 		folio_put(folio);
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 276720bc18dc52..af415293e2651f 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -105,6 +105,12 @@ static void iomap_set_range_uptodate(struct folio *folio, size_t off,
 		folio_mark_uptodate(folio);
 }
 
+void iomap_folio_mark_uptodate(struct folio *folio)
+{
+	iomap_set_range_uptodate(folio, 0, folio_size(folio));
+}
+EXPORT_SYMBOL_GPL(iomap_folio_mark_uptodate);
+
 /*
  * Find the next dirty block in the folio. end_blk is inclusive.
  * If no dirty block is found, this will return end_blk + 1.
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 56b43d594e6e29..40aa3476a351d2 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -365,6 +365,7 @@ struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len);
 bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags);
 void iomap_invalidate_folio(struct folio *folio, size_t offset, size_t len);
 bool iomap_dirty_folio(struct address_space *mapping, struct folio *folio);
+void iomap_folio_mark_uptodate(struct folio *folio);
 int iomap_file_unshare(struct inode *inode, loff_t pos, loff_t len,
 		const struct iomap_ops *ops,
 		const struct iomap_write_ops *write_ops);

gemini-3.1-pro-preview

null

null

							input: 3132
							output: 31
							thoughts: 304
						

**Analyzing a FUSE/IOMAP Patch for Fuzzing Potential**

Okay, so I've got a patch in front of me that touches some pretty fundamental areas: `fs/fuse/file.c`, `fs/fuse/notify.c`, `fs/iomap/buffered-io.c`, and `include/linux/iomap.h`. Immediately, my spidey-sense is tingling. This isn't just a minor tweak; we're talking about core FUSE and IOMAP logic, and that's *always* worth a closer look from a fuzzing perspective.

Essentially, the patch introduces this new `iomap_folio_mark_uptodate(struct folio *folio)` function, which seems to centralize the marking of folios as up-to-date. It's calling the IOMAP-specific function to mark the entire folio, replacing the more generic `folio_mark_uptodate` calls in `fuse_fill_write_pages` and `fuse_notify_store`. On top of that, it removes some existing error handling/short write handling from `fuse_send_write_pages` which clears the up-to-date flag, which, by itself, is interesting. This looks like a simplification and potential optimization, but that always introduces a new vector for attack.

My initial gut feeling is that this *is* fuzzable, and *should* be fuzzed, as there's a good probability that there are functional areas, and that these areas are reachable, and the changes are significant enough to warrant investigation.

Specifically, I'll want to focus on: `fuse_send_write_pages`, `fuse_fill_write_pages`, `fuse_notify_store`, and now, critically, the new `iomap_folio_mark_uptodate` function. These are the key symbols impacted by the patch.

Now, I need to make sure I'm building this with the right configurations. Clearly, `FUSE_FS` is required. I'll also need `FS_IOMAP`. Since IOMAP is often enabled as a dependency of other filesystems, I need to double-check that this is a configurable option.

I'll check the `fs/fuse/Kconfig` and `fs/iomap/Kconfig` files just to be absolutely certain. The sooner I build the fuzzing build, the sooner I can start actually digging into this.

{
  "Expression": "config FUSE_FS",
  "PathPrefix": "fs/fuse/Kconfig"
}

{
  "Output": "fs/fuse/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/fuse/Kconfig:2:config FUSE_FS\nfs/fuse/Kconfig-3-\ttristate \"FUSE (Filesystem in Userspace) support\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 4071
							output: 34
							thoughts: 17
						

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Investigating a Potential I/O Mapping Issue**

Alright, the user's probably encountering a problem related to file I/O mapping. My immediate instinct is to dive into the kernel configuration files, specifically anything dealing with I/O mapping. Let's see... a good starting point would be `fs/iomap/Kconfig` or something similar within the file system core. That's usually where the knobs and features related to how file systems handle direct I/O, buffered I/O, and related optimizations are defined. Chances are, the relevant configuration options are documented there, alongside the dependencies that impact their availability or behavior. I'll need to understand the implications of different settings to diagnose the user's issue effectively.

no matches

{
  "Expression": "config FS_IOMAP",
  "PathPrefix": "fs/iomap/Kconfig"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 4311
							output: 30
							thoughts: 15
						

Okay, let's dive into this. Here's my thought process on this:

**Locating the Definition of `FS_IOMAP`**

Alright, so I need to find the definition of `FS_IOMAP`. This is a pretty straightforward starting point. I understand the importance of knowing where this particular macro or symbol is defined. Is it in the kernel headers, in a specific library, or maybe even in a userspace include file? It could be anywhere, really. But to effectively work with or analyze anything related to `FS_IOMAP`, locating its declaration is absolutely essential. That's my initial goal. Knowing the definition is the foundation for understanding its purpose and how it's used within a system.

{
  "Expression": "config FS_IOMAP",
  "PathPrefix": "fs/Kconfig"
}

{
  "Output": "fs/Kconfig=12=config VALIDATE_FS_PARSER\n--\nfs/Kconfig-17-\nfs/Kconfig:18:config FS_IOMAP\nfs/Kconfig-19-\tbool\n"
}

gemini-3.1-pro-preview

null

null

							input: 4577
							output: 32
							thoughts: 438
						

**FUSE Write Path Analysis**

Okay, so I'm looking at this patch and my initial thought is, `FS_IOMAP` is a boolean. Usually, I see other filesystems setting this, so let's check for other configs. The primary relevant one here seems to be `FUSE_FS`.

Alright, let's zero in on the key symbols involved. I see `fuse_send_write_pages`, `fuse_fill_write_pages`, `fuse_notify_store`, and `iomap_folio_mark_uptodate` as the key functions to watch. I should figure out if each are static or exported. 

`fuse_send_write_pages` and `fuse_fill_write_pages` are static and found in `fs/fuse/file.c`, and `fuse_notify_store` is also static in `fs/fuse/notify.c`, while `iomap_folio_mark_uptodate` is exported from `fs/iomap/buffered-io.c`.

Now, is `fuse_send_write_pages` a hot path? Given its name, it's called during write pages, and that's an obvious candidate for fuzzing in FUSE! Good.

Let's quickly verify the metadata. Yep, `WorthFuzzing` is `true`. The reasoning makes perfect sense: it touches page uptodate handling in FUSE write and notification paths, and introduces an iomap helper, and all these things are functional changes user-space can trigger via FUSE. The `FocusSymbols` are spot on, and `FUSE_FS` is the required `EnableConfig`.

Just to be absolutely sure, I'll double-check if `FS_IOMAP` requires explicit enabling. Since it's a `bool` without a prompt, it's selected by other configs, not directly enabled via menuconfig. So does FUSE select it? Let's check `fs/fuse/Kconfig` to be sure.

{
  "Expression": "select FS_IOMAP",
  "PathPrefix": "fs/fuse/Kconfig"
}

{
  "Output": "fs/fuse/Kconfig=2=config FUSE_FS\n--\nfs/fuse/Kconfig-4-\tselect FS_POSIX_ACL\nfs/fuse/Kconfig:5:\tselect FS_IOMAP\nfs/fuse/Kconfig-6-\thelp\n"
}

gemini-3.1-pro-preview

null

null

							input: 5559
							output: 122
							thoughts: 34
						

Okay, here's my interpretation of those thoughts, summarized in the first person, assuming the context is file system design and the user is an expert:

**File System Feature Enablement**

Right, so `FUSE_FS` automatically triggers the use of `FS_IOMAP`. That's efficient. It makes the dependency clear. Essentially, by enabling `FUSE_FS`, I'm implicitly activating the I/O mapping strategy. That's good; it simplifies the configuration and avoids redundancy in feature settings. No need to explicitly enable both. It's a nice, clean architectural design choice.

Therefore, the next step is straightforward: I will configure the relevant settings based on this new understanding and set the results accordingly, knowing that everything is as it should be.

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_fill_write_pages",
    "fuse_notify_store",
    "iomap_folio_mark_uptodate"
  ],
  "Reasoning": "The patch modifies page uptodate handling in FUSE write and notify paths, and introduces a new iomap helper. These are functional changes in filesystem logic that can be triggered by user-space via FUSE.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_fill_write_pages",
    "fuse_notify_store",
    "iomap_folio_mark_uptodate"
  ],
  "Reasoning": "The patch modifies page uptodate handling in FUSE write and notify paths, and introduces a new iomap helper. These are functional changes in filesystem logic that can be triggered by user-space via FUSE.",
  "WorthFuzzing": true
}