AI Trajectory

null

{
  "EnableConfigs": [
    "EXFAT_FS"
  ],
  "FocusSymbols": [
    "__exfat_cache_inval_inode",
    "exfat_file_write_iter",
    "__exfat_iomap_begin",
    "exfat_iomap_valid",
    "exfat_writeback_range"
  ],
  "Reasoning": "The patch modifies the exfat filesystem's iomap and caching logic, specifically introducing a validity cookie for iomaps and changing how the cache validity ID is incremented. These changes are functional and reachable from userspace via file write and writeback operations.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 27522b3586de807fe95bc86e883a95cde8d02328\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Jul 1 06:48:28 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/fs/exfat/cache.c b/fs/exfat/cache.c\nindex 7c8b4182f5de7b..71631bab182cd1 100644\n--- a/fs/exfat/cache.c\n+++ b/fs/exfat/cache.c\n@@ -228,9 +228,10 @@ static void __exfat_cache_inval_inode(struct inode *inode)\n \t\texfat_cache_free(cache);\n \t}\n \t/* Update. The copy of caches before this id is discarded. */\n-\tei-\u003ecache_valid_id++;\n-\tif (ei-\u003ecache_valid_id == EXFAT_CACHE_VALID)\n-\t\tei-\u003ecache_valid_id++;\n+\tif (ei-\u003ecache_valid_id + 1 == EXFAT_CACHE_VALID)\n+\t\tei-\u003ecache_valid_id = EXFAT_CACHE_VALID + 1;\n+\telse\n+\t\tei-\u003ecache_valid_id = ei-\u003ecache_valid_id + 1;\n }\n \n void exfat_cache_inval_inode(struct inode *inode)\ndiff --git a/fs/exfat/file.c b/fs/exfat/file.c\nindex 5fc13378d35f72..4258398ca641f0 100644\n--- a/fs/exfat/file.c\n+++ b/fs/exfat/file.c\n@@ -772,8 +772,8 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)\n \tif (iocb-\u003eki_flags \u0026 IOCB_DIRECT)\n \t\tret = exfat_dio_write_iter(iocb, iter);\n \telse\n-\t\tret = iomap_file_buffered_write(iocb, iter,\n-\t\t\t\t\u0026exfat_write_iomap_ops, NULL, NULL);\n+\t\tret = iomap_file_buffered_write(iocb, iter, \u0026exfat_write_iomap_ops,\n+\t\t\t\t\t\t\u0026exfat_iomap_write_ops, NULL);\n \tif (ret \u003c 0)\n \t\tgoto unlock;\n \ndiff --git a/fs/exfat/iomap.c b/fs/exfat/iomap.c\nindex 1aac38e63fe6f0..efced320a5efba 100644\n--- a/fs/exfat/iomap.c\n+++ b/fs/exfat/iomap.c\n@@ -56,6 +56,7 @@ static int __exfat_iomap_begin(struct inode *inode, loff_t offset, loff_t length\n \t\t\tiomap-\u003eaddr = IOMAP_NULL_ADDR;\n \t\t\tiomap-\u003eoffset = offset;\n \t\t\tiomap-\u003elength = length;\n+\t\t\tiomap-\u003evalidity_cookie = ei-\u003ecache_valid_id;\n \t\t\treturn 0;\n \t\t}\n \n@@ -133,7 +134,7 @@ static int __exfat_iomap_begin(struct inode *inode, loff_t offset, loff_t length\n \t\t}\n \t}\n \n-\tiomap-\u003eflags |= IOMAP_F_MERGED;\n+\tiomap-\u003evalidity_cookie = ei-\u003ecache_valid_id;\n out:\n \tmutex_unlock(\u0026sbi-\u003es_lock);\n \treturn err;\n@@ -155,6 +156,15 @@ const struct iomap_ops exfat_iomap_ops = {\n \t.iomap_begin = exfat_iomap_begin,\n };\n \n+static bool exfat_iomap_valid(struct inode *inode, const struct iomap *iomap)\n+{\n+\treturn EXFAT_I(inode)-\u003ecache_valid_id == iomap-\u003evalidity_cookie;\n+}\n+\n+const struct iomap_write_ops exfat_iomap_write_ops = {\n+\t.iomap_valid = exfat_iomap_valid,\n+};\n+\n /*\n  * exfat_write_iomap_end - Update the state after write\n  *\n@@ -201,7 +211,8 @@ static ssize_t exfat_writeback_range(struct iomap_writepage_ctx *wpc,\n \t\tstruct folio *folio, u64 offset, unsigned int len, u64 end_pos)\n {\n \tif (offset \u003c wpc-\u003eiomap.offset ||\n-\t    offset \u003e= wpc-\u003eiomap.offset + wpc-\u003eiomap.length) {\n+\t    offset \u003e= wpc-\u003eiomap.offset + wpc-\u003eiomap.length ||\n+\t    !exfat_iomap_valid(wpc-\u003einode, \u0026wpc-\u003eiomap)) {\n \t\tint error;\n \n \t\terror = __exfat_iomap_begin(wpc-\u003einode, offset, len,\ndiff --git a/fs/exfat/iomap.h b/fs/exfat/iomap.h\nindex fd8a913f779460..39c93f8cd7904d 100644\n--- a/fs/exfat/iomap.h\n+++ b/fs/exfat/iomap.h\n@@ -9,6 +9,7 @@\n extern const struct iomap_dio_ops exfat_write_dio_ops;\n extern const struct iomap_ops exfat_iomap_ops;\n extern const struct iomap_ops exfat_write_iomap_ops;\n+extern const struct iomap_write_ops exfat_iomap_write_ops;\n extern const struct iomap_writeback_ops exfat_writeback_ops;\n extern const struct iomap_read_ops exfat_iomap_bio_read_ops;\n \n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "EXFAT_FS"
  ],
  "FocusSymbols": [
    "__exfat_cache_inval_inode",
    "exfat_file_write_iter",
    "__exfat_iomap_begin",
    "exfat_iomap_valid",
    "exfat_writeback_range"
  ],
  "Reasoning": "The patch modifies the exfat filesystem's iomap and caching logic, specifically introducing a validity cookie for iomaps and changing how the cache validity ID is incremented. These changes are functional and reachable from userspace via file write and writeback operations.",
  "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 27522b3586de807fe95bc86e883a95cde8d02328
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Jul 1 06:48:28 2026 +0000

    syz-cluster: applied patch under review

diff --git a/fs/exfat/cache.c b/fs/exfat/cache.c
index 7c8b4182f5de7b..71631bab182cd1 100644
--- a/fs/exfat/cache.c
+++ b/fs/exfat/cache.c
@@ -228,9 +228,10 @@ static void __exfat_cache_inval_inode(struct inode *inode)
 		exfat_cache_free(cache);
 	}
 	/* Update. The copy of caches before this id is discarded. */
-	ei->cache_valid_id++;
-	if (ei->cache_valid_id == EXFAT_CACHE_VALID)
-		ei->cache_valid_id++;
+	if (ei->cache_valid_id + 1 == EXFAT_CACHE_VALID)
+		ei->cache_valid_id = EXFAT_CACHE_VALID + 1;
+	else
+		ei->cache_valid_id = ei->cache_valid_id + 1;
 }
 
 void exfat_cache_inval_inode(struct inode *inode)
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 5fc13378d35f72..4258398ca641f0 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -772,8 +772,8 @@ static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	if (iocb->ki_flags & IOCB_DIRECT)
 		ret = exfat_dio_write_iter(iocb, iter);
 	else
-		ret = iomap_file_buffered_write(iocb, iter,
-				&exfat_write_iomap_ops, NULL, NULL);
+		ret = iomap_file_buffered_write(iocb, iter, &exfat_write_iomap_ops,
+						&exfat_iomap_write_ops, NULL);
 	if (ret < 0)
 		goto unlock;
 
diff --git a/fs/exfat/iomap.c b/fs/exfat/iomap.c
index 1aac38e63fe6f0..efced320a5efba 100644
--- a/fs/exfat/iomap.c
+++ b/fs/exfat/iomap.c
@@ -56,6 +56,7 @@ static int __exfat_iomap_begin(struct inode *inode, loff_t offset, loff_t length
 			iomap->addr = IOMAP_NULL_ADDR;
 			iomap->offset = offset;
 			iomap->length = length;
+			iomap->validity_cookie = ei->cache_valid_id;
 			return 0;
 		}
 
@@ -133,7 +134,7 @@ static int __exfat_iomap_begin(struct inode *inode, loff_t offset, loff_t length
 		}
 	}
 
-	iomap->flags |= IOMAP_F_MERGED;
+	iomap->validity_cookie = ei->cache_valid_id;
 out:
 	mutex_unlock(&sbi->s_lock);
 	return err;
@@ -155,6 +156,15 @@ const struct iomap_ops exfat_iomap_ops = {
 	.iomap_begin = exfat_iomap_begin,
 };
 
+static bool exfat_iomap_valid(struct inode *inode, const struct iomap *iomap)
+{
+	return EXFAT_I(inode)->cache_valid_id == iomap->validity_cookie;
+}
+
+const struct iomap_write_ops exfat_iomap_write_ops = {
+	.iomap_valid = exfat_iomap_valid,
+};
+
 /*
  * exfat_write_iomap_end - Update the state after write
  *
@@ -201,7 +211,8 @@ static ssize_t exfat_writeback_range(struct iomap_writepage_ctx *wpc,
 		struct folio *folio, u64 offset, unsigned int len, u64 end_pos)
 {
 	if (offset < wpc->iomap.offset ||
-	    offset >= wpc->iomap.offset + wpc->iomap.length) {
+	    offset >= wpc->iomap.offset + wpc->iomap.length ||
+	    !exfat_iomap_valid(wpc->inode, &wpc->iomap)) {
 		int error;
 
 		error = __exfat_iomap_begin(wpc->inode, offset, len,
diff --git a/fs/exfat/iomap.h b/fs/exfat/iomap.h
index fd8a913f779460..39c93f8cd7904d 100644
--- a/fs/exfat/iomap.h
+++ b/fs/exfat/iomap.h
@@ -9,6 +9,7 @@
 extern const struct iomap_dio_ops exfat_write_dio_ops;
 extern const struct iomap_ops exfat_iomap_ops;
 extern const struct iomap_ops exfat_write_iomap_ops;
+extern const struct iomap_write_ops exfat_iomap_write_ops;
 extern const struct iomap_writeback_ops exfat_writeback_ops;
 extern const struct iomap_read_ops exfat_iomap_bio_read_ops;
 

gemini-3.1-pro-preview

null

null

							input: 3103
							output: 32
							thoughts: 287
						

**Analyzing a Proposed ExFAT Patch**

Okay, so I'm looking at this patch for the exFAT filesystem, and it's touching a few key areas: `cache.c`, `file.c`, `iomap.c`, and `iomap.h`. That immediately tells me this is something substantial, likely a functional change, not just a bug fix.

The core of the change seems to revolve around how `cache_valid_id` is handled, specifically within `__exfat_cache_inval_inode`.  They're incrementing it there, and then setting `iomap->validity_cookie` to that new value in `__exfat_iomap_begin`.  A new function, `exfat_iomap_valid`, is introduced, which I assume checks for the validity of the cached data based on comparing `EXFAT_I(inode)->cache_valid_id` with that cookie. This implies some form of cache invalidation or tracking.

I see that `&exfat_iomap_write_ops` is now passed to `iomap_file_buffered_write`. That's an interesting hook; it must be related to how the write operation is performed, possibly dealing with buffered writes or I/O mapping. And then there's a check for `!exfat_iomap_valid` inside `exfat_writeback_range`. This is definitely a crucial area to understand in context of this modification.

Given these changes, especially the manipulation of the `cache_valid_id` and the introduction of a new validity check, this screams "fuzzing target" to me. There are several interesting states that could be uncovered here. Any change that deals with caching and I/O mapping is very likely to have some interesting edge cases, race conditions, or other potential bugs that can be revealed via fuzzing.

My next step is to find the relevant configuration option for exFAT. I'll use `grepper` and look for `EXFAT_FS` in `fs/exfat/Kconfig` to determine how to enable/disable it and ensure it's properly configured for testing.

{
  "Expression": "config EXFAT_FS",
  "PathPrefix": "fs/exfat/Kconfig"
}

{
  "Output": "fs/exfat/Kconfig-2-\nfs/exfat/Kconfig:3:config EXFAT_FS\nfs/exfat/Kconfig-4-\ttristate \"exFAT filesystem support\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 3946
							output: 207
							thoughts: 261
						

**Analyzing the Recent EXFAT Changes**

Okay, so the configuration is definitely targeting `EXFAT_FS`. My focus now is on the recent modifications, specifically these functions: `__exfat_cache_inval_inode`, `exfat_file_write_iter`, `__exfat_iomap_begin`, `exfat_iomap_valid`, and `exfat_writeback_range`. I'm already seeing some patterns. `__exfat_cache_inval_inode` is static, called by `exfat_cache_inval_inode`, I'll keep that in mind. `exfat_file_write_iter` is the file write iterator, that makes sense. `__exfat_iomap_begin` is the iomap begin, which, I suppose could be interesting. And the `exfat_iomap_valid` and `exfat_writeback_range` functions are there too.

Just double-checking, I want to make sure the implementation of `exfat_iomap_valid` is static; yes, it's defined as such in `fs/exfat/iomap.c`. And now, let's also investigate `exfat_writeback_range` within the same file. I think I'll use `grepper` to locate the source definitions.

{
  "Expression": "^static void __exfat_cache_inval_inode",
  "PathPrefix": "fs/exfat/cache.c"
}

{
  "Output": "fs/exfat/cache.c=162=static void exfat_cache_add(struct inode *inode,\n--\nfs/exfat/cache.c-217- */\nfs/exfat/cache.c:218:static void __exfat_cache_inval_inode(struct inode *inode)\nfs/exfat/cache.c-219-{\n"
}

{
  "Expression": "^static ssize_t exfat_file_write_iter",
  "PathPrefix": "fs/exfat/file.c"
}

{
  "Output": "fs/exfat/file.c=708=static ssize_t exfat_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)\n--\nfs/exfat/file.c-730-\nfs/exfat/file.c:731:static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)\nfs/exfat/file.c-732-{\n"
}

{
  "Expression": "^static int __exfat_iomap_begin",
  "PathPrefix": "fs/exfat/iomap.c"
}

{
  "Output": "fs/exfat/iomap.c=37=const struct iomap_dio_ops exfat_write_dio_ops = {\n--\nfs/exfat/iomap.c-40-\nfs/exfat/iomap.c:41:static int __exfat_iomap_begin(struct inode *inode, loff_t offset, loff_t length,\nfs/exfat/iomap.c-42-\t\tunsigned int flags, struct iomap *iomap, bool may_alloc)\n"
}

{
  "Expression": "^static bool exfat_iomap_valid",
  "PathPrefix": "fs/exfat/iomap.c"
}

{
  "Output": "fs/exfat/iomap.c=155=const struct iomap_ops exfat_iomap_ops = {\n--\nfs/exfat/iomap.c-158-\nfs/exfat/iomap.c:159:static bool exfat_iomap_valid(struct inode *inode, const struct iomap *iomap)\nfs/exfat/iomap.c-160-{\n"
}

{
  "Expression": "^static ssize_t exfat_writeback_range",
  "PathPrefix": "fs/exfat/iomap.c"
}

{
  "Output": "fs/exfat/iomap.c=199=const struct iomap_ops exfat_write_iomap_ops = {\n--\nfs/exfat/iomap.c-209- */\nfs/exfat/iomap.c:210:static ssize_t exfat_writeback_range(struct iomap_writepage_ctx *wpc,\nfs/exfat/iomap.c-211-\t\tstruct folio *folio, u64 offset, unsigned int len, u64 end_pos)\n"
}

gemini-3.1-pro-preview

null

null

							input: 5337
							output: 146
							thoughts: 219
						

**Adding ExFAT I/O and Caching Functions to FocusSymbols**

Okay, so I've got these functions: `__exfat_cache_inval_inode`, `exfat_file_write_iter`, `__exfat_iomap_begin`, `exfat_iomap_valid`, and `exfat_writeback_range`. Based on the patch description, these functions are all involved in the ExFAT filesystem's iomap and caching mechanisms. This is pretty significant, and they're definitely reachable from userspace, which makes them prime candidates for inclusion in `FocusSymbols`. Essentially, it seems this patch is changing how writes and writebacks operate.

Let's quickly verify the naming. Yeah, all the function names are correct. Excellent. I'm satisfied. Now, it's time to call `set-results`.

{
  "EnableConfigs": [
    "EXFAT_FS"
  ],
  "FocusSymbols": [
    "__exfat_cache_inval_inode",
    "exfat_file_write_iter",
    "__exfat_iomap_begin",
    "exfat_iomap_valid",
    "exfat_writeback_range"
  ],
  "Reasoning": "The patch modifies the exfat filesystem's iomap and caching logic, specifically introducing a validity cookie for iomaps and changing how the cache validity ID is incremented. These changes are functional and reachable from userspace via file write and writeback operations.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "EXFAT_FS"
  ],
  "FocusSymbols": [
    "__exfat_cache_inval_inode",
    "exfat_file_write_iter",
    "__exfat_iomap_begin",
    "exfat_iomap_valid",
    "exfat_writeback_range"
  ],
  "Reasoning": "The patch modifies the exfat filesystem's iomap and caching logic, specifically introducing a validity cookie for iomaps and changing how the cache validity ID is incremented. These changes are functional and reachable from userspace via file write and writeback operations.",
  "WorthFuzzing": true
}