AI Trajectory

null

{
  "EnableConfigs": [
    "AFFS_FS"
  ],
  "FocusSymbols": [
    "affs_grow_extcache",
    "affs_evict_inode"
  ],
  "Reasoning": "The patch changes the memory allocator used for the extension cache in the AFFS filesystem from the page allocator to the slab allocator. This is a functional change that affects memory management and should be fuzzed to ensure no memory leaks or corruption occur.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 55fded7345507add74aba15d82311fa706083170\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Tue Jul 14 09:21:59 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/fs/affs/file.c b/fs/affs/file.c\nindex 144b17482d12da..b8da8c54e0d748 100644\n--- a/fs/affs/file.c\n+++ b/fs/affs/file.c\n@@ -56,11 +56,13 @@ affs_grow_extcache(struct inode *inode, u32 lc_idx)\n \tint i, j, key;\n \n \tif (!AFFS_I(inode)-\u003ei_lc) {\n-\t\tchar *ptr = (char *)get_zeroed_page(GFP_NOFS);\n-\t\tif (!ptr)\n+\t\tu32 *lc;\n+\n+\t\tlc = kzalloc(AFFS_CACHE_SIZE, GFP_NOFS);\n+\t\tif (!lc)\n \t\t\treturn -ENOMEM;\n-\t\tAFFS_I(inode)-\u003ei_lc = (u32 *)ptr;\n-\t\tAFFS_I(inode)-\u003ei_ac = (struct affs_ext_key *)(ptr + AFFS_CACHE_SIZE / 2);\n+\t\tAFFS_I(inode)-\u003ei_lc = lc;\n+\t\tAFFS_I(inode)-\u003ei_ac = (struct affs_ext_key *)(lc + AFFS_LC_SIZE);\n \t}\n \n \tlc_max = AFFS_LC_SIZE \u003c\u003c AFFS_I(inode)-\u003ei_lc_shift;\ndiff --git a/fs/affs/inode.c b/fs/affs/inode.c\nindex 5dd1b016bcb00a..07c3a6376aaa1b 100644\n--- a/fs/affs/inode.c\n+++ b/fs/affs/inode.c\n@@ -258,7 +258,7 @@ affs_setattr(struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *attr)\n void\n affs_evict_inode(struct inode *inode)\n {\n-\tunsigned long cache_page;\n+\tu32 *lc;\n \tpr_debug(\"evict_inode(ino=%llu, nlink=%u)\\n\",\n \t\t inode-\u003ei_ino, inode-\u003ei_nlink);\n \ttruncate_inode_pages_final(\u0026inode-\u003ei_data);\n@@ -273,12 +273,12 @@ affs_evict_inode(struct inode *inode)\n \tmmb_invalidate(\u0026AFFS_I(inode)-\u003ei_metadata_bhs);\n \tclear_inode(inode);\n \taffs_free_prealloc(inode);\n-\tcache_page = (unsigned long)AFFS_I(inode)-\u003ei_lc;\n-\tif (cache_page) {\n+\tlc = AFFS_I(inode)-\u003ei_lc;\n+\tif (lc) {\n \t\tpr_debug(\"freeing ext cache\\n\");\n \t\tAFFS_I(inode)-\u003ei_lc = NULL;\n \t\tAFFS_I(inode)-\u003ei_ac = NULL;\n-\t\tfree_page(cache_page);\n+\t\tkfree(lc);\n \t}\n \taffs_brelse(AFFS_I(inode)-\u003ei_ext_bh);\n \tAFFS_I(inode)-\u003ei_ext_last = ~1;\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "AFFS_FS"
  ],
  "FocusSymbols": [
    "affs_grow_extcache",
    "affs_evict_inode"
  ],
  "Reasoning": "The patch changes the memory allocator used for the extension cache in the AFFS filesystem from the page allocator to the slab allocator. This is a functional change that affects memory management and should be fuzzed to ensure no memory leaks or corruption occur.",
  "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 55fded7345507add74aba15d82311fa706083170
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Jul 14 09:21:59 2026 +0000

    syz-cluster: applied patch under review

diff --git a/fs/affs/file.c b/fs/affs/file.c
index 144b17482d12da..b8da8c54e0d748 100644
--- a/fs/affs/file.c
+++ b/fs/affs/file.c
@@ -56,11 +56,13 @@ affs_grow_extcache(struct inode *inode, u32 lc_idx)
 	int i, j, key;
 
 	if (!AFFS_I(inode)->i_lc) {
-		char *ptr = (char *)get_zeroed_page(GFP_NOFS);
-		if (!ptr)
+		u32 *lc;
+
+		lc = kzalloc(AFFS_CACHE_SIZE, GFP_NOFS);
+		if (!lc)
 			return -ENOMEM;
-		AFFS_I(inode)->i_lc = (u32 *)ptr;
-		AFFS_I(inode)->i_ac = (struct affs_ext_key *)(ptr + AFFS_CACHE_SIZE / 2);
+		AFFS_I(inode)->i_lc = lc;
+		AFFS_I(inode)->i_ac = (struct affs_ext_key *)(lc + AFFS_LC_SIZE);
 	}
 
 	lc_max = AFFS_LC_SIZE << AFFS_I(inode)->i_lc_shift;
diff --git a/fs/affs/inode.c b/fs/affs/inode.c
index 5dd1b016bcb00a..07c3a6376aaa1b 100644
--- a/fs/affs/inode.c
+++ b/fs/affs/inode.c
@@ -258,7 +258,7 @@ affs_setattr(struct mnt_idmap *idmap, struct dentry *dentry, struct iattr *attr)
 void
 affs_evict_inode(struct inode *inode)
 {
-	unsigned long cache_page;
+	u32 *lc;
 	pr_debug("evict_inode(ino=%llu, nlink=%u)\n",
 		 inode->i_ino, inode->i_nlink);
 	truncate_inode_pages_final(&inode->i_data);
@@ -273,12 +273,12 @@ affs_evict_inode(struct inode *inode)
 	mmb_invalidate(&AFFS_I(inode)->i_metadata_bhs);
 	clear_inode(inode);
 	affs_free_prealloc(inode);
-	cache_page = (unsigned long)AFFS_I(inode)->i_lc;
-	if (cache_page) {
+	lc = AFFS_I(inode)->i_lc;
+	if (lc) {
 		pr_debug("freeing ext cache\n");
 		AFFS_I(inode)->i_lc = NULL;
 		AFFS_I(inode)->i_ac = NULL;
-		free_page(cache_page);
+		kfree(lc);
 	}
 	affs_brelse(AFFS_I(inode)->i_ext_bh);
 	AFFS_I(inode)->i_ext_last = ~1;

gemini-3.1-pro-preview

null

null

							input: 2443
							output: 31
							thoughts: 81
						

**Analyzing the AFFS Filesystem Patch**

Okay, so this patch is clearly messing with the `affs` filesystem, which is interesting. The core of the change seems to be around how the extension cache is allocated. Specifically, it's switching from using `get_zeroed_page` to `kzalloc`. This immediately makes me think about memory allocation strategies and potential performance implications. `kzalloc` zeroes the allocated memory, unlike `get_zeroed_page` which just maps a page and potentially could include stale data. This is good for security, potentially preventing information leaks.

The size of this cache, `AFFS_CACHE_SIZE`, is the key factor. I need to understand its size to appreciate the magnitude of this change and whether or not performance would be impacted by clearing the memory with `kzalloc`. I'll need to go digging in `fs/affs/affs.h` to confirm the value of `AFFS_CACHE_SIZE`. I'm hoping it isn't too large, or this could impact performance.

{
  "Expression": "AFFS_CACHE_SIZE",
  "PathPrefix": "fs/affs/"
}

{
  "Output": "fs/affs/affs.h-25-\nfs/affs/affs.h:26:#define AFFS_CACHE_SIZE\t\tPAGE_SIZE\nfs/affs/affs.h-27-\nfs/affs/affs.h:28:#define AFFS_LC_SIZE\t\t(AFFS_CACHE_SIZE/sizeof(u32)/2)\nfs/affs/affs.h:29:#define AFFS_AC_SIZE\t\t(AFFS_CACHE_SIZE/sizeof(struct affs_ext_key)/2)\nfs/affs/affs.h-30-#define AFFS_AC_MASK\t\t(AFFS_AC_SIZE-1)\n--\nfs/affs/file.c=51=affs_grow_extcache(struct inode *inode, u32 lc_idx)\n--\nfs/affs/file.c-60-\nfs/affs/file.c:61:\t\tlc = kzalloc(AFFS_CACHE_SIZE, GFP_NOFS);\nfs/affs/file.c-62-\t\tif (!lc)\n"
}

gemini-3.1-pro-preview

null

null

							input: 3053
							output: 30
							thoughts: 416
						

**Analyzing the AFFS Cache Allocation Change**

Okay, so this patch is switching how the AFFS filesystem allocates and frees its cache. Initially, it used `get_zeroed_page(GFP_NOFS)`, obtaining a zeroed page and casting it to a `char *`. The critical part here is that `AFFS_I(inode)->i_lc` was set to `(u32 *)ptr`, and `AFFS_I(inode)->i_ac` was set to an offset within that page. Now, the patch is swapping this for `kzalloc(AFFS_CACHE_SIZE, GFP_NOFS)`. Since `AFFS_CACHE_SIZE` *is* `PAGE_SIZE`, the allocated memory size is the same. The `lc` which is `u32 *` is being moved to point to the newly allocated memory.

The crucial detail is that the offset calculation for `i_ac` is unchanged. Previously, `i_ac` was located at `ptr + AFFS_CACHE_SIZE / 2`. Now, it’s being set to `(lc + AFFS_LC_SIZE)`. We need to be sure that the offset remains the same. Since `lc` is a `u32 *`, the offset is calculated in units of `sizeof(u32)`. `AFFS_LC_SIZE` is defined as `(AFFS_CACHE_SIZE / sizeof(u32) / 2)`. Therefore `AFFS_LC_SIZE * sizeof(u32)` becomes `AFFS_CACHE_SIZE / 2`. So, the offset for `i_ac` *is* identical, preserving the original memory layout.

The real difference is in the allocation and deallocation methods. We’re changing from `free_page(cache_page)` to `kfree(lc)`. This indicates a shift from the page allocator to the slab allocator. This is a functional change as it alters how memory is managed within the filesystem, which is likely to have performance implications.

Given that this is touching filesystem code, and particularly, the AFFS filesystem, which may have its own quirks, it's absolutely worth fuzzing this change. It's a change in how memory is allocated and freed, so there’s potential for subtle bugs. Now, before I start the fuzzing process, let me quickly double-check the configuration for AFFS.

{
  "Expression": "config AFFS_FS",
  "PathPrefix": "fs/affs/"
}

{
  "Output": "fs/affs/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/affs/Kconfig:2:config AFFS_FS\nfs/affs/Kconfig-3-\ttristate \"Amiga FFS file system support\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 4088
							output: 105
							thoughts: 117
						

**Analyzing AFFS Filesystem Configuration**

Okay, so the configuration in play here is `AFFS_FS`. Right, got it. I'm focusing in on modifications made to the `affs_grow_extcache` and `affs_evict_inode` functions. Let's start by adding both `affs_grow_extcache` and `affs_evict_inode` to the `FocusSymbols` list. I'll need to remember to check for any *other* relevant functions, just to be thorough. Now, let's see, I believe `affs_grow_extcache` is defined within `fs/affs/file.c`, and `affs_evict_inode` is in `fs/affs/inode.c`. That's where to find those.

{
  "EnableConfigs": [
    "AFFS_FS"
  ],
  "FocusSymbols": [
    "affs_grow_extcache",
    "affs_evict_inode"
  ],
  "Reasoning": "The patch changes the memory allocator used for the extension cache in the AFFS filesystem from the page allocator to the slab allocator. This is a functional change that affects memory management and should be fuzzed to ensure no memory leaks or corruption occur.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "AFFS_FS"
  ],
  "FocusSymbols": [
    "affs_grow_extcache",
    "affs_evict_inode"
  ],
  "Reasoning": "The patch changes the memory allocator used for the extension cache in the AFFS filesystem from the page allocator to the slab allocator. This is a functional change that affects memory management and should be fuzzed to ensure no memory leaks or corruption occur.",
  "WorthFuzzing": true
}