AI Trajectory

null

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_perform_write"
  ],
  "Reasoning": "The patch modifies the logic for handling write pages in FUSE, specifically removing the short write and folio uptodate clearing logic in `fuse_send_write_pages`. This is a functional change in the FUSE filesystem core logic.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 97118d4267595aa3eb659d0108ee22283307bfb4\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Fri Jun 26 11:43:23 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/fs/fuse/file.c b/fs/fuse/file.c\nindex cb8da4c06d17e0..c4ae4009a423d2 100644\n--- a/fs/fuse/file.c\n+++ b/fs/fuse/file.c\n@@ -1227,8 +1227,7 @@ 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@@ -1243,24 +1242,9 @@ 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"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_perform_write"
  ],
  "Reasoning": "The patch modifies the logic for handling write pages in FUSE, specifically removing the short write and folio uptodate clearing logic in `fuse_send_write_pages`. This is a functional change in the FUSE filesystem core logic.",
  "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 97118d4267595aa3eb659d0108ee22283307bfb4
Author: syz-cluster <triage@syzkaller.com>
Date:   Fri Jun 26 11:43:23 2026 +0000

    syz-cluster: applied patch under review

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index cb8da4c06d17e0..c4ae4009a423d2 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1227,8 +1227,7 @@ 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++)
@@ -1243,24 +1242,9 @@ 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);

gemini-3.1-pro-preview

null

null

							input: 2139
							output: 34
							thoughts: 104
						

**Analyzing a FUSE Filesystem Patch**

Okay, so I've got a patch here affecting `fs/fuse/file.c`, specifically around `fuse_send_write_pages`. I see that some code is being removed, and it's all clustered around how the function handles `short_write`, `offset`, and `count`. It looks like we're losing the `folio_clear_uptodate(folio)` calls, which is interesting - that's a key function for maintaining data consistency, so I'll need to understand the implications of removing it. We're also dropping the tracking of the `count` variable. This is definitely a functional change in the FUSE filesystem behavior. Time to delve into `fuse_send_write_pages` itself and figure out *why* this change is happening and, more importantly, *what* the consequences are. This requires an in-depth code review to fully appreciate the impact of these deletions.

{
  "Expression": "fuse_send_write_pages",
  "PathPrefix": "fs/fuse/file.c"
}

{
  "Output": "fs/fuse/file.c=1203=bool fuse_write_update_attr(struct inode *inode, loff_t pos, ssize_t written)\n--\nfs/fuse/file.c-1221-\nfs/fuse/file.c:1222:static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,\nfs/fuse/file.c-1223-\t\t\t\t     struct kiocb *iocb, struct inode *inode,\n--\nfs/fuse/file.c=1348=static ssize_t fuse_perform_write(struct kiocb *iocb, struct iov_iter *ii)\n--\nfs/fuse/file.c-1377-\t\t} else {\nfs/fuse/file.c:1378:\t\t\terr = fuse_send_write_pages(\u0026ia, iocb, inode,\nfs/fuse/file.c-1379-\t\t\t\t\t\t    pos, count);\n"
}

gemini-3.1-pro-preview

null

null

							input: 2726
							output: 29
							thoughts: 102
						

**FUSE Write Page Function Analysis**

Okay, so `fuse_send_write_pages` is called by `fuse_perform_write`, which means it's pretty central to how FUSE handles write operations. That alone makes it a prime candidate for fuzzing; any functional changes in FUSE deserve a good look. We need to understand its behavior thoroughly. Let's dig into `fuse_send_write_pages` to get a handle on what it's actually doing and decide if we are going to dive in.

Given that FUSE is known to be reachable and testable, this looks like a worthwhile pursuit.

Before we dedicate more time, I'll quickly check `fs/fuse/Kconfig`. There might be some specific configurations or build options that affect this particular function, which could be useful to know before starting.

{
  "Expression": "config FUSE",
  "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--\nfs/fuse/Kconfig=32=config VIRTIO_FS\n--\nfs/fuse/Kconfig-42-\nfs/fuse/Kconfig:43:config FUSE_DAX\nfs/fuse/Kconfig-44-\tbool \"Virtio Filesystem Direct Host Memory Access support\"\n--\nfs/fuse/Kconfig-56-\nfs/fuse/Kconfig:57:config FUSE_PASSTHROUGH\nfs/fuse/Kconfig-58-\tbool \"FUSE passthrough operations support\"\n--\nfs/fuse/Kconfig-67-\nfs/fuse/Kconfig:68:config FUSE_IO_URING\nfs/fuse/Kconfig-69-\tbool \"FUSE communication over io-uring\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 3290
							output: 102
							thoughts: 104
						

**Analyzing the FUSE File System Configuration**

Okay, so the primary configuration involved here is `FUSE_FS`. My initial focus is on the `fuse_send_write_pages` function, as the patch seems to center around it. I need to understand the implications of this change. To that end, I should also look at the `fuse_perform_write` function; it seems a likely point of interaction.

Let's quickly verify that `FUSE_FS` is the *only* significant configuration variable driving this change. It would be detrimental to miss a related variable.

Now, with this information established, I can go ahead and `set-results`. I have enough to begin forming a deeper understanding of the code.

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_perform_write"
  ],
  "Reasoning": "The patch modifies the logic for handling write pages in FUSE, specifically removing the short write and folio uptodate clearing logic in `fuse_send_write_pages`. This is a functional change in the FUSE filesystem core logic.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "FUSE_FS"
  ],
  "FocusSymbols": [
    "fuse_send_write_pages",
    "fuse_perform_write"
  ],
  "Reasoning": "The patch modifies the logic for handling write pages in FUSE, specifically removing the short write and folio uptodate clearing logic in `fuse_send_write_pages`. This is a functional change in the FUSE filesystem core logic.",
  "WorthFuzzing": true
}