AI Trajectory

null

{
  "EnableConfigs": [
    "SWAP"
  ],
  "FocusSymbols": [
    "do_swap_page",
    "get_swap_device",
    "read_swap_cache_async",
    "swap_retry_table_alloc",
    "swp_swapcount",
    "swap_put_entries_direct"
  ],
  "KMSANReasoning": "The patch modifies the error handling of `get_swap_device()` to return `ERR_PTR(-EIO)` for bad swap entries instead of just `NULL`, and updates all callers to check for `IS_ERR_OR_NULL(si)`. In `do_swap_page()`, it translates the error into a `VM_FAULT_SIGBUS`. These changes are purely related to control flow and error propagation in the memory management subsystem (swap handling). They do not introduce any new allocations, do not expose kernel structures to user space, and do not involve any uninitialized memory risks. Therefore, a dedicated KMSAN fuzzing session is not necessary, as standard KASAN and other bug detectors are sufficient to catch any potential memory corruption or logic bugs in this area.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch modifies `get_swap_device()` to return `ERR_PTR(-EIO)` instead of `NULL` for bad swap entries, and updates multiple callers across the memory management subsystem (including `do_swap_page`, `shmem_swapin_folio`, `read_swap_cache_async`, etc.) to handle this new error return via `IS_ERR_OR_NULL`. This is a functional change in core swap logic that directly affects page fault handling and swap operations, making it highly relevant for fuzzing.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 93d12fdc6d180508294b1a036ed911bdbe96dfbb\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Tue Aug 18 10:50:03 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/mm/memory.c b/mm/memory.c\nindex 4134ac607ee0f..be980bb2e3347 100644\n--- a/mm/memory.c\n+++ b/mm/memory.c\n@@ -4954,10 +4954,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)\n \t\tgoto out;\n \t}\n \n-\t/* Prevent swapoff from happening to us. */\n+\t/* Prevent swapoff from happening to us, and reject a bad entry. */\n \tsi = get_swap_device(entry);\n-\tif (unlikely(!si))\n+\tif (IS_ERR_OR_NULL(si)) {\n+\t\tif (IS_ERR(si))\n+\t\t\tret = VM_FAULT_SIGBUS;\n \t\tgoto out;\n+\t}\n \n \tfolio = swap_cache_get_folio(entry);\n \tif (folio)\n@@ -5266,7 +5269,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)\n \tif (vmf-\u003epte)\n \t\tpte_unmap_unlock(vmf-\u003epte, vmf-\u003eptl);\n out:\n-\tif (si)\n+\tif (!IS_ERR_OR_NULL(si))\n \t\tput_swap_device(si);\n \treturn ret;\n out_nomap:\ndiff --git a/mm/mincore.c b/mm/mincore.c\nindex ff4ac82817683..c086836bc4bcc 100644\n--- a/mm/mincore.c\n+++ b/mm/mincore.c\n@@ -71,7 +71,7 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem)\n \t */\n \tif (shmem) {\n \t\tsi = get_swap_device(entry);\n-\t\tif (!si)\n+\t\tif (IS_ERR_OR_NULL(si))\n \t\t\treturn 0;\n \t}\n \tfolio = swap_cache_get_folio(entry);\ndiff --git a/mm/shmem.c b/mm/shmem.c\nindex 599665a3d6e7b..553c95d3341d2 100644\n--- a/mm/shmem.c\n+++ b/mm/shmem.c\n@@ -2277,7 +2277,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,\n \n \tsi = get_swap_device(index_entry);\n \torder = shmem_confirm_swap(mapping, index, index_entry);\n-\tif (unlikely(!si)) {\n+\tif (IS_ERR_OR_NULL(si)) {\n \t\tif (order \u003c 0)\n \t\t\treturn -EEXIST;\n \t\telse\ndiff --git a/mm/swap_state.c b/mm/swap_state.c\nindex b76eb3d876fd7..2edbd2aafd669 100644\n--- a/mm/swap_state.c\n+++ b/mm/swap_state.c\n@@ -716,7 +716,7 @@ struct folio *read_swap_cache_async(struct swap_io_ctx *ctx, swp_entry_t entry,\n \tstruct folio *folio;\n \n \tsi = get_swap_device(entry);\n-\tif (!si)\n+\tif (IS_ERR_OR_NULL(si))\n \t\treturn NULL;\n \n \tmpol = get_vma_policy(vma, addr, 0, \u0026ilx);\n@@ -952,7 +952,7 @@ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,\n \t\t */\n \t\tif (swp_type(entry) != swp_type(targ_entry)) {\n \t\t\tsi = get_swap_device(entry);\n-\t\t\tif (!si)\n+\t\t\tif (IS_ERR_OR_NULL(si))\n \t\t\t\tcontinue;\n \t\t}\n \t\tfolio = swap_cache_read_folio(\u0026ctx, entry, gfp_mask, mpol, ilx,\ndiff --git a/mm/swapfile.c b/mm/swapfile.c\nindex f5dfc7e59191e..806c048ab6f7e 100644\n--- a/mm/swapfile.c\n+++ b/mm/swapfile.c\n@@ -1504,7 +1504,7 @@ int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp)\n \tunsigned long offset = swp_offset(entry);\n \n \tsi = get_swap_device(entry);\n-\tif (!si)\n+\tif (IS_ERR_OR_NULL(si))\n \t\treturn 0;\n \n \tci = __swap_offset_to_cluster(si, offset);\n@@ -1859,7 +1859,10 @@ void folio_put_swap(struct folio *folio, struct page *page)\n  * Check whether swap entry is valid in the swap device.  If so,\n  * return pointer to swap_info_struct, and keep the swap entry valid\n  * via preventing the swap device from being swapoff, until\n- * put_swap_device() is called.  Otherwise return NULL.\n+ * put_swap_device() is called.  Return NULL for an empty entry or a\n+ * device that is going away, and ERR_PTR(-EIO) if the entry's type\n+ * names no swap device or its offset is past the end of one. These EIOs\n+ * are preceded by pr_err().\n  *\n  * Notice that swapoff or swapoff+swapon can still happen before the\n  * percpu_ref_tryget_live() in get_swap_device() or after the\n@@ -1900,12 +1903,13 @@ struct swap_info_struct *get_swap_device(swp_entry_t entry)\n \treturn si;\n bad_nofile:\n \tpr_err(\"%s: %s%08lx\\n\", __func__, Bad_file, entry.val);\n+\treturn ERR_PTR(-EIO);\n out:\n \treturn NULL;\n put_out:\n \tpr_err(\"%s: %s%08lx\\n\", __func__, Bad_offset, entry.val);\n \tpercpu_ref_put(\u0026si-\u003eusers);\n-\treturn NULL;\n+\treturn ERR_PTR(-EIO);\n }\n \n /*\n@@ -2001,7 +2005,7 @@ int swp_swapcount(swp_entry_t entry)\n \tint count;\n \n \tsi = get_swap_device(entry);\n-\tif (!si)\n+\tif (IS_ERR_OR_NULL(si))\n \t\treturn 0;\n \n \tci = swap_cluster_lock(si, swp_offset(entry));\n@@ -2127,7 +2131,7 @@ void swap_put_entries_direct(swp_entry_t entry, int nr)\n \tstruct swap_info_struct *si;\n \n \tsi = get_swap_device(entry);\n-\tif (WARN_ON_ONCE(!si))\n+\tif (WARN_ON_ONCE(IS_ERR_OR_NULL(si)))\n \t\treturn;\n \tif (WARN_ON_ONCE(end_offset \u003e si-\u003emax))\n \t\tgoto out;\ndiff --git a/mm/userfaultfd.c b/mm/userfaultfd.c\nindex 23fb68fce000e..878e27f571638 100644\n--- a/mm/userfaultfd.c\n+++ b/mm/userfaultfd.c\n@@ -1700,7 +1700,7 @@ static long move_pages_ptes(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd\n \t\t}\n \n \t\tsi = get_swap_device(entry);\n-\t\tif (unlikely(!si)) {\n+\t\tif (IS_ERR_OR_NULL(si)) {\n \t\t\tret = -EAGAIN;\n \t\t\tgoto out;\n \t\t}\n@@ -1757,7 +1757,7 @@ static long move_pages_ptes(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd\n \tif (dst_pte)\n \t\tpte_unmap(dst_pte);\n \tmmu_notifier_invalidate_range_end(\u0026range);\n-\tif (si)\n+\tif (!IS_ERR_OR_NULL(si))\n \t\tput_swap_device(si);\n \n \treturn ret;\ndiff --git a/mm/zswap.c b/mm/zswap.c\nindex 37f34e406c8e3..1d11f350ac1e1 100644\n--- a/mm/zswap.c\n+++ b/mm/zswap.c\n@@ -997,7 +997,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,\n \n \t/* try to allocate swap cache folio */\n \tsi = get_swap_device(swpentry);\n-\tif (!si)\n+\tif (IS_ERR_OR_NULL(si))\n \t\treturn -EEXIST;\n \n \tmpol = get_task_policy(current);\n"
}

best-expensive

null

{
  "EnableConfigs": [
    "SWAP"
  ],
  "FocusSymbols": [
    "do_swap_page",
    "get_swap_device",
    "read_swap_cache_async",
    "swap_retry_table_alloc",
    "swp_swapcount",
    "swap_put_entries_direct"
  ],
  "Reasoning": "The patch modifies `get_swap_device()` to return `ERR_PTR(-EIO)` instead of `NULL` for bad swap entries, and updates multiple callers across the memory management subsystem (including `do_swap_page`, `shmem_swapin_folio`, `read_swap_cache_async`, etc.) to handle this new error return via `IS_ERR_OR_NULL`. This is a functional change in core swap logic that directly affects page fault handling and swap operations, making it highly relevant for fuzzing.",
  "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).
- Code in vendor-specific PCIe switch, SmartNIC, or GPU drivers (e.g., mlxsw, pds_core, qed,
  ionic, amdgpu) that require physical PCIe hardware cards not emulated in standard QEMU.
- Driver .remove, .shutdown, or pci_unregister_driver teardown callbacks (e.g., igb_remove)
  that are executed only during PCI hot-unplug or sysfs driver unbind operations.

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.
   Prefer non-static, non-inlined API entrypoint functions over internal static helper functions
   (which are inlined by the compiler and do not have distinct symbol addresses).
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.
   Also check "depends on" lines in Kconfig to include any non-standard parent subsystem configs
   needed for Kbuild to compile the code statically into vmlinux. 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 93d12fdc6d180508294b1a036ed911bdbe96dfbb
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Aug 18 10:50:03 2026 +0000

    syz-cluster: applied patch under review

diff --git a/mm/memory.c b/mm/memory.c
index 4134ac607ee0f..be980bb2e3347 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4954,10 +4954,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		goto out;
 	}
 
-	/* Prevent swapoff from happening to us. */
+	/* Prevent swapoff from happening to us, and reject a bad entry. */
 	si = get_swap_device(entry);
-	if (unlikely(!si))
+	if (IS_ERR_OR_NULL(si)) {
+		if (IS_ERR(si))
+			ret = VM_FAULT_SIGBUS;
 		goto out;
+	}
 
 	folio = swap_cache_get_folio(entry);
 	if (folio)
@@ -5266,7 +5269,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	if (vmf->pte)
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
 out:
-	if (si)
+	if (!IS_ERR_OR_NULL(si))
 		put_swap_device(si);
 	return ret;
 out_nomap:
diff --git a/mm/mincore.c b/mm/mincore.c
index ff4ac82817683..c086836bc4bcc 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -71,7 +71,7 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem)
 	 */
 	if (shmem) {
 		si = get_swap_device(entry);
-		if (!si)
+		if (IS_ERR_OR_NULL(si))
 			return 0;
 	}
 	folio = swap_cache_get_folio(entry);
diff --git a/mm/shmem.c b/mm/shmem.c
index 599665a3d6e7b..553c95d3341d2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2277,7 +2277,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 
 	si = get_swap_device(index_entry);
 	order = shmem_confirm_swap(mapping, index, index_entry);
-	if (unlikely(!si)) {
+	if (IS_ERR_OR_NULL(si)) {
 		if (order < 0)
 			return -EEXIST;
 		else
diff --git a/mm/swap_state.c b/mm/swap_state.c
index b76eb3d876fd7..2edbd2aafd669 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -716,7 +716,7 @@ struct folio *read_swap_cache_async(struct swap_io_ctx *ctx, swp_entry_t entry,
 	struct folio *folio;
 
 	si = get_swap_device(entry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return NULL;
 
 	mpol = get_vma_policy(vma, addr, 0, &ilx);
@@ -952,7 +952,7 @@ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
 		 */
 		if (swp_type(entry) != swp_type(targ_entry)) {
 			si = get_swap_device(entry);
-			if (!si)
+			if (IS_ERR_OR_NULL(si))
 				continue;
 		}
 		folio = swap_cache_read_folio(&ctx, entry, gfp_mask, mpol, ilx,
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f5dfc7e59191e..806c048ab6f7e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1504,7 +1504,7 @@ int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp)
 	unsigned long offset = swp_offset(entry);
 
 	si = get_swap_device(entry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return 0;
 
 	ci = __swap_offset_to_cluster(si, offset);
@@ -1859,7 +1859,10 @@ void folio_put_swap(struct folio *folio, struct page *page)
  * Check whether swap entry is valid in the swap device.  If so,
  * return pointer to swap_info_struct, and keep the swap entry valid
  * via preventing the swap device from being swapoff, until
- * put_swap_device() is called.  Otherwise return NULL.
+ * put_swap_device() is called.  Return NULL for an empty entry or a
+ * device that is going away, and ERR_PTR(-EIO) if the entry's type
+ * names no swap device or its offset is past the end of one. These EIOs
+ * are preceded by pr_err().
  *
  * Notice that swapoff or swapoff+swapon can still happen before the
  * percpu_ref_tryget_live() in get_swap_device() or after the
@@ -1900,12 +1903,13 @@ struct swap_info_struct *get_swap_device(swp_entry_t entry)
 	return si;
 bad_nofile:
 	pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
+	return ERR_PTR(-EIO);
 out:
 	return NULL;
 put_out:
 	pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
 	percpu_ref_put(&si->users);
-	return NULL;
+	return ERR_PTR(-EIO);
 }
 
 /*
@@ -2001,7 +2005,7 @@ int swp_swapcount(swp_entry_t entry)
 	int count;
 
 	si = get_swap_device(entry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return 0;
 
 	ci = swap_cluster_lock(si, swp_offset(entry));
@@ -2127,7 +2131,7 @@ void swap_put_entries_direct(swp_entry_t entry, int nr)
 	struct swap_info_struct *si;
 
 	si = get_swap_device(entry);
-	if (WARN_ON_ONCE(!si))
+	if (WARN_ON_ONCE(IS_ERR_OR_NULL(si)))
 		return;
 	if (WARN_ON_ONCE(end_offset > si->max))
 		goto out;
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 23fb68fce000e..878e27f571638 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1700,7 +1700,7 @@ static long move_pages_ptes(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd
 		}
 
 		si = get_swap_device(entry);
-		if (unlikely(!si)) {
+		if (IS_ERR_OR_NULL(si)) {
 			ret = -EAGAIN;
 			goto out;
 		}
@@ -1757,7 +1757,7 @@ static long move_pages_ptes(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd
 	if (dst_pte)
 		pte_unmap(dst_pte);
 	mmu_notifier_invalidate_range_end(&range);
-	if (si)
+	if (!IS_ERR_OR_NULL(si))
 		put_swap_device(si);
 
 	return ret;
diff --git a/mm/zswap.c b/mm/zswap.c
index 37f34e406c8e3..1d11f350ac1e1 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -997,7 +997,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 
 	/* try to allocate swap cache folio */
 	si = get_swap_device(swpentry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return -EEXIST;
 
 	mpol = get_task_policy(current);

gemini-3.1-pro-preview

null

null

							input: 4192
							output: 81
							thoughts: 712
						

**Analyzing a Critical Swap Subsystem Change**

Okay, so I'm looking at a patch that's touched quite a few files within the memory management subsystem: `mm/memory.c`, `mm/mincore.c`, `mm/shmem.c`, `mm/swap_state.c`, `mm/swapfile.c`, `mm/userfaultfd.c`, and `mm/zswap.c`. My initial reaction is that this warrants some serious attention – these are core components we're dealing with. The key change seems to be in `get_swap_device()`. It's now returning `ERR_PTR(-EIO)` instead of `NULL` when it encounters a bad file or offset, which is then leading to updated checks using `IS_ERR_OR_NULL(si)` instead of the previous `!si`.

Specifically, in `do_swap_page()`, a swap entry that previously might have been silently ignored or treated as empty now triggers a `VM_FAULT_SIGBUS` if `IS_ERR(si)` is true. This is a pretty significant shift; we're now explicitly signaling an error rather than implicitly handling it. I need to understand the implications of this change and how it impacts error handling and the overall behavior of the system under these swap conditions.

I'm thinking this is a prime candidate for fuzzing. To get started, I'm identifying key symbols to target. Initially, I noted `do_swap_page`, `get_swap_device`, `shmem_swapin_folio`, `read_swap_cache_async`, `swap_vma_readahead`, `swap_retry_table_alloc`, `swp_swapcount`, `swap_put_entries_direct`, `move_pages_ptes`, and `zswap_writeback_entry`.

However, the prompt is reminding me to focus on non-static, non-inlined API entrypoints to avoid inlined helpers. Based on this, I'll focus my fuzzing efforts on: `do_swap_page`, `get_swap_device`, `read_swap_cache_async`, `swap_retry_table_alloc`, `swp_swapcount`, and `swap_put_entries_direct`. These seem like the most relevant entry points that provide the needed information. I'll need to verify each of these in detail.

{
  "Expression": "^(struct folio \\*|int|void|struct swap_info_struct \\*|vm_fault_t) (do_swap_page|get_swap_device|read_swap_cache_async|swap_retry_table_alloc|swp_swapcount|swap_put_entries_direct)\\("
}

{
  "Output": "include/linux/swap.h=398=int swap_dup_entry_direct(swp_entry_t entry);\ninclude/linux/swap.h:399:void swap_put_entries_direct(swp_entry_t entry, int nr);\ninclude/linux/swap.h-400-\n--\nmm/internal.h=567=static inline vm_fault_t vmf_anon_prepare(struct vm_fault *vmf)\n--\nmm/internal.h-575-\nmm/internal.h:576:vm_fault_t do_swap_page(struct vm_fault *vmf);\nmm/internal.h-577-void folio_rotate_reclaimable(struct folio *folio);\n--\nmm/memory.c=4863=static void check_swap_exclusive(struct folio *folio, swp_entry_t entry,\n--\nmm/memory.c-4880- */\nmm/memory.c:4881:vm_fault_t do_swap_page(struct vm_fault *vmf)\nmm/memory.c-4882-{\n--\nmm/swapfile.c=1463=static int swap_extend_table_alloc(struct swap_info_struct *si,\n--\nmm/swapfile.c-1498-\nmm/swapfile.c:1499:int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp)\nmm/swapfile.c-1500-{\n--\nmm/swapfile.c=1983=bool swap_entry_swapped(struct swap_info_struct *si, swp_entry_t entry)\n--\nmm/swapfile.c-1999- */\nmm/swapfile.c:2000:int swp_swapcount(swp_entry_t entry)\nmm/swapfile.c-2001-{\n--\nmm/swapfile.c=2101=bool folio_free_swap(struct folio *folio)\n--\nmm/swapfile.c-2125- */\nmm/swapfile.c:2126:void swap_put_entries_direct(swp_entry_t entry, int nr)\nmm/swapfile.c-2127-{\n"
}

gemini-3.1-pro-preview

null

null

							input: 6065
							output: 43
							thoughts: 21
						

Here's my thought process, as though I were considering those functions:

**Analyzing Swap Device and Cache Operations**

Okay, let's dive into these functions: `get_swap_device` and `read_swap_cache_async`. I want to quickly assess their roles in the memory management scheme. `get_swap_device` is the starting point, of course; it's the gatekeeper. My immediate questions are: how robust is its device detection? Does it handle multiple swap partitions gracefully? Does it allow for dynamic addition/removal of swap devices? I'll probably want to look for edge cases in the error handling. I wonder how it interacts with the underlying kernel calls or system configuration files.

Then we've got `read_swap_cache_async`. The "async" tag immediately grabs my attention. This suggests a non-blocking operation, which is critical for maintaining performance. I need to understand the concurrency model used. Is it leveraging threads, or perhaps an event-driven architecture? I'll need to see the synchronization primitives employed – are we talking mutexes, semaphores, or something more specialized for asynchronous I/O? What's the error handling like if the read fails? Does it retry, or propagate the error? And how is it integrating with the cache itself? Is it an LRU cache, a write-back cache, or something else entirely? What are the implications for data consistency and durability in case of a crash? I'll be looking for potential race conditions or deadlocks, especially since it's asynchronous. Ultimately, the efficiency of this asynchronous read is paramount to the overall performance of the swap system. I'll need to verify that it's implemented correctly and efficiently.

no matches

{
  "Expression": "^(struct folio \\*|struct swap_info_struct \\*) (get_swap_device|read_swap_cache_async)\\("
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 6504
							output: 32
							thoughts: 44
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Debugging Swap Device Identification**

Right, so `get_swap_device` isn't showing up as expected. My initial thought is it's either an `inline static` function, and therefore potentially not being generated as a standalone symbol, or perhaps my regex for symbol matching is too specific and I'm missing it entirely. Time to dig into the source. I'll start by checking `mm/swapfile.c` and `mm/swap_state.c`. That's where I'd expect to find the core swap file management logic and state handling. Those are likely candidates given the name, so I'll see what's what in there. Let's see if the relevant code is declared directly in those files or if they are calling some other function.

{
  "Expression": "get_swap_device\\(",
  "PathPrefix": "mm/swapfile.c"
}

{
  "Output": "mm/swapfile.c=1499=int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp)\n--\nmm/swapfile.c-1505-\nmm/swapfile.c:1506:\tsi = get_swap_device(entry);\nmm/swapfile.c-1507-\tif (IS_ERR_OR_NULL(si))\n--\nmm/swapfile.c=1830=void folio_put_swap(struct folio *folio, struct page *page)\n--\nmm/swapfile.c-1851- * because of swapoff.  Then, we need to enclose all swap related\nmm/swapfile.c:1852: * functions with get_swap_device() and put_swap_device(), unless the\nmm/swapfile.c-1853- * swap functions call get/put_swap_device() by themselves.\n--\nmm/swapfile.c-1867- * Notice that swapoff or swapoff+swapon can still happen before the\nmm/swapfile.c:1868: * percpu_ref_tryget_live() in get_swap_device() or after the\nmm/swapfile.c-1869- * percpu_ref_put() in put_swap_device() if there isn't any other way\n--\nmm/swapfile.c-1886- */\nmm/swapfile.c:1887:struct swap_info_struct *get_swap_device(swp_entry_t entry)\nmm/swapfile.c-1888-{\n--\nmm/swapfile.c=2000=int swp_swapcount(swp_entry_t entry)\n--\nmm/swapfile.c-2006-\nmm/swapfile.c:2007:\tsi = get_swap_device(entry);\nmm/swapfile.c-2008-\tif (IS_ERR_OR_NULL(si))\n--\nmm/swapfile.c=2126=void swap_put_entries_direct(swp_entry_t entry, int nr)\n--\nmm/swapfile.c-2132-\nmm/swapfile.c:2133:\tsi = get_swap_device(entry);\nmm/swapfile.c-2134-\tif (WARN_ON_ONCE(IS_ERR_OR_NULL(si)))\n"
}

gemini-3.1-pro-preview

null

null

							input: 7364
							output: 35
							thoughts: 55
						

Okay, here's my take on those code snippets, thinking through the implications as I'd approach this as an expert:

**Navigating the Swap Subsystem**

Alright, let's see...I'm tracing through the swap code here. So, `struct swap_info_struct *get_swap_device(swp_entry_t entry)` – that's the core function for figuring out *which* swap device a particular page entry, `entry`, corresponds to. I'd expect it to handle the logic of mapping a swap entry to a physical swap partition, taking care of any necessary bookkeeping. The fact that it's defined in `mm/swapfile.c` makes perfect sense. It’s the low-level stuff, the file system interaction within the swap context. Gotta love those naming conventions.

Then we've got `read_swap_cache_async`, hanging out in `mm/swap_state.c`. That's interesting. The `_async` suffix makes me think it's dealing with asynchronous swap operations – likely an implementation of read-ahead or some form of I/O completion. It's probably responsible for initiating the process of fetching the swapped page from disk into the page cache, which is what I'd expect given the location of the file. So, we're talking about the interplay between swap space and the page cache in a performance-critical way, with an eye towards concurrency. Looks like the asynchronous design could provide a significant performance boost. Interesting.

{
  "Expression": "read_swap_cache_async\\(",
  "PathPrefix": "mm/swap_state.c"
}

{
  "Output": "mm/swap_state.c=683=struct folio *swapin_sync(swp_entry_t entry, gfp_t gfp, unsigned long orders,\n--\nmm/swap_state.c-709- */\nmm/swap_state.c:710:struct folio *read_swap_cache_async(struct swap_io_ctx *ctx, swp_entry_t entry,\nmm/swap_state.c-711-\t\tgfp_t gfp_mask, struct vm_area_struct *vma, unsigned long addr)\n"
}

gemini-3.1-pro-preview

null

null

							input: 7919
							output: 27
							thoughts: 85
						

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

**Analyzing the Swap Device Patch**

Okay, this looks like a solid change. The patch is modifying `get_swap_device` so it's returning `ERR_PTR(-EIO)` when it hits a bad swap entry. That's a good approach; error propagation is always important in memory management. It also looks like the callers have been updated to handle the new return code, which is exactly what I'd expect. So, functionally, we've got a slightly more robust swap management system here. This is definitely a functional change in the swap handling. Now, the question is, what config option enables this feature? I need to figure out which `CONFIG_` option enables the swap functions, and thus, this change. I'll need to check either `mm/Makefile` or `mm/Kconfig` to pinpoint whether `CONFIG_SWAP` is actually the correct one, or if it's dependent on a more specific sub-option. I'll dig into the build files and see what I find.

{
  "Expression": "swapfile\\.o",
  "PathPrefix": "mm/Makefile"
}

{
  "Output": "mm/Makefile=76=endif\nmm/Makefile-77-\nmm/Makefile:78:obj-$(CONFIG_SWAP)\t+= page_io.o swap_state.o swapfile.o\nmm/Makefile-79-obj-$(CONFIG_ZSWAP)\t+= zswap.o\n"
}

gemini-3.1-pro-preview

null

null

							input: 8348
							output: 27
							thoughts: 59
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Memory Management Configuration Considerations**

Right, so we're looking at memory management configuration options, specifically the ones that impact how the system handles swapping and shared memory. The initial trigger was `CONFIG_SWAP`, of course, that's fundamental. But then it branches out. We also need to factor in `CONFIG_ZSWAP`. That's definitely going to impact the build process of `mm/zswap.c`. We need to be confident of how that compiles.

Now, my mind moves to `CONFIG_SHMEM`. The question here is whether or not that always compiles `mm/shmem.c`. I'm pretty sure the answer is yes, but I need to quickly verify that. There may be some edge cases that I am overlooking, so let's quickly double-check the Kconfig dependencies. It's important to understand the build implications here to avoid any unwanted surprises down the line.

{
  "Expression": "shmem\\.o",
  "PathPrefix": "mm/Makefile"
}

{
  "Output": "mm/Makefile=51=obj-y\t\t\t:= filemap.o mempool.o oom_kill.o fadvise.o \\\n--\nmm/Makefile-53-\t\t\t   readahead.o folio.o truncate.o vmscan.o shrinker.o \\\nmm/Makefile:54:\t\t\t   shmem.o util.o mmzone.o vmstat.o backing-dev.o \\\nmm/Makefile-55-\t\t\t   mm_init.o percpu.o slab_common.o \\\n"
}

gemini-3.1-pro-preview

null

null

							input: 8777
							output: 28
							thoughts: 23
						

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

**Checking Compilation Dependencies**

Right, so `shmem.o` is a given; that's always built. No surprises there. But now I need to double-check my mental map... what's the deal with `userfaultfd.o`? Does that always get compiled, or is it conditional? I need to remember the specific build flags and configurations that determine its inclusion. I need to refresh my memory on the intricacies of that particular module. Time to dig in and clarify that dependency.

{
  "Expression": "userfaultfd\\.o",
  "PathPrefix": "mm/Makefile"
}

{
  "Output": "mm/Makefile=131=obj-$(CONFIG_CMA_SYSFS) += cma_sysfs.o\nmm/Makefile:132:obj-$(CONFIG_USERFAULTFD) += userfaultfd.o\nmm/Makefile-133-obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o\n"
}

gemini-3.1-pro-preview

null

null

							input: 9046
							output: 199
							thoughts: 449
						

**Analyzing the Swap Patch for Fuzzing Potential**

Okay, so I'm looking at this patch and immediately, `CONFIG_USERFAULTFD` pops out because it ties into `mm/userfaultfd.c`. But the meat of this change really looks to be centered around `get_swap_device` and `do_swap_page`, and those are clearly under `CONFIG_SWAP`. Right, that's the key. I'll definitely be enabling `SWAP` in `EnableConfigs`.

Now, let's drill down into the key functions. I've got to keep an eye on: `do_swap_page`, `get_swap_device`, `read_swap_cache_async`, `swap_retry_table_alloc`, `swp_swapcount`, and `swap_put_entries_direct`.

First, a quick check to see if any of those are static. Nope, they're all exported. Good, that makes things easier.

Now, let's take a closer look at `do_swap_page`. Aha, it's right there in `mm/memory.c`, a core page fault handler. It's clear that `get_swap_device` is the function that's being directly modified.

This is significant. The patch changes how `get_swap_device()` handles errors. Instead of returning `NULL` for bad swap entries, it's now returning `ERR_PTR(-EIO)`. And, critically, it updates all the relevant callers across the memory management subsystem, including `do_swap_page`, `shmem_swapin_folio`, and `read_swap_cache_async`, to properly handle this new error return using `IS_ERR_OR_NULL`. This change in the core swap logic which directly affects page fault handling and swap operations, making it highly relevant for fuzzing.

Therefore, the patch is changing the way swap errors are handled at a fundamental level. I'm going to set `WorthFuzzing=true` because this change has direct implications for memory management stability.

{
  "EnableConfigs": [
    "SWAP"
  ],
  "FocusSymbols": [
    "do_swap_page",
    "get_swap_device",
    "read_swap_cache_async",
    "swap_retry_table_alloc",
    "swp_swapcount",
    "swap_put_entries_direct"
  ],
  "Reasoning": "The patch modifies `get_swap_device()` to return `ERR_PTR(-EIO)` instead of `NULL` for bad swap entries, and updates multiple callers across the memory management subsystem (including `do_swap_page`, `shmem_swapin_folio`, `read_swap_cache_async`, etc.) to handle this new error return via `IS_ERR_OR_NULL`. This is a functional change in core swap logic that directly affects page fault handling and swap operations, making it highly relevant for fuzzing.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "SWAP"
  ],
  "FocusSymbols": [
    "do_swap_page",
    "get_swap_device",
    "read_swap_cache_async",
    "swap_retry_table_alloc",
    "swp_swapcount",
    "swap_put_entries_direct"
  ],
  "Reasoning": "The patch modifies `get_swap_device()` to return `ERR_PTR(-EIO)` instead of `NULL` for bad swap entries, and updates multiple callers across the memory management subsystem (including `do_swap_page`, `shmem_swapin_folio`, `read_swap_cache_async`, etc.) to handle this new error return via `IS_ERR_OR_NULL`. This is a functional change in core swap logic that directly affects page fault handling and swap operations, making it highly relevant for fuzzing.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

best-expensive

null

{
  "KMSANReasoning": "The patch modifies the error handling of `get_swap_device()` to return `ERR_PTR(-EIO)` for bad swap entries instead of just `NULL`, and updates all callers to check for `IS_ERR_OR_NULL(si)`. In `do_swap_page()`, it translates the error into a `VM_FAULT_SIGBUS`. These changes are purely related to control flow and error propagation in the memory management subsystem (swap handling). They do not introduce any new allocations, do not expose kernel structures to user space, and do not involve any uninitialized memory risks. Therefore, a dedicated KMSAN fuzzing session is not necessary, as standard KASAN and other bug detectors are sufficient to catch any potential memory corruption or logic bugs in this area.",
  "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.

For your convenience, here is the diff of the changes:
commit 93d12fdc6d180508294b1a036ed911bdbe96dfbb
Author: syz-cluster <triage@syzkaller.com>
Date:   Tue Aug 18 10:50:03 2026 +0000

    syz-cluster: applied patch under review

diff --git a/mm/memory.c b/mm/memory.c
index 4134ac607ee0f..be980bb2e3347 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4954,10 +4954,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		goto out;
 	}
 
-	/* Prevent swapoff from happening to us. */
+	/* Prevent swapoff from happening to us, and reject a bad entry. */
 	si = get_swap_device(entry);
-	if (unlikely(!si))
+	if (IS_ERR_OR_NULL(si)) {
+		if (IS_ERR(si))
+			ret = VM_FAULT_SIGBUS;
 		goto out;
+	}
 
 	folio = swap_cache_get_folio(entry);
 	if (folio)
@@ -5266,7 +5269,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	if (vmf->pte)
 		pte_unmap_unlock(vmf->pte, vmf->ptl);
 out:
-	if (si)
+	if (!IS_ERR_OR_NULL(si))
 		put_swap_device(si);
 	return ret;
 out_nomap:
diff --git a/mm/mincore.c b/mm/mincore.c
index ff4ac82817683..c086836bc4bcc 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -71,7 +71,7 @@ static unsigned char mincore_swap(swp_entry_t entry, bool shmem)
 	 */
 	if (shmem) {
 		si = get_swap_device(entry);
-		if (!si)
+		if (IS_ERR_OR_NULL(si))
 			return 0;
 	}
 	folio = swap_cache_get_folio(entry);
diff --git a/mm/shmem.c b/mm/shmem.c
index 599665a3d6e7b..553c95d3341d2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2277,7 +2277,7 @@ static int shmem_swapin_folio(struct inode *inode, pgoff_t index,
 
 	si = get_swap_device(index_entry);
 	order = shmem_confirm_swap(mapping, index, index_entry);
-	if (unlikely(!si)) {
+	if (IS_ERR_OR_NULL(si)) {
 		if (order < 0)
 			return -EEXIST;
 		else
diff --git a/mm/swap_state.c b/mm/swap_state.c
index b76eb3d876fd7..2edbd2aafd669 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -716,7 +716,7 @@ struct folio *read_swap_cache_async(struct swap_io_ctx *ctx, swp_entry_t entry,
 	struct folio *folio;
 
 	si = get_swap_device(entry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return NULL;
 
 	mpol = get_vma_policy(vma, addr, 0, &ilx);
@@ -952,7 +952,7 @@ static struct folio *swap_vma_readahead(swp_entry_t targ_entry, gfp_t gfp_mask,
 		 */
 		if (swp_type(entry) != swp_type(targ_entry)) {
 			si = get_swap_device(entry);
-			if (!si)
+			if (IS_ERR_OR_NULL(si))
 				continue;
 		}
 		folio = swap_cache_read_folio(&ctx, entry, gfp_mask, mpol, ilx,
diff --git a/mm/swapfile.c b/mm/swapfile.c
index f5dfc7e59191e..806c048ab6f7e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1504,7 +1504,7 @@ int swap_retry_table_alloc(swp_entry_t entry, gfp_t gfp)
 	unsigned long offset = swp_offset(entry);
 
 	si = get_swap_device(entry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return 0;
 
 	ci = __swap_offset_to_cluster(si, offset);
@@ -1859,7 +1859,10 @@ void folio_put_swap(struct folio *folio, struct page *page)
  * Check whether swap entry is valid in the swap device.  If so,
  * return pointer to swap_info_struct, and keep the swap entry valid
  * via preventing the swap device from being swapoff, until
- * put_swap_device() is called.  Otherwise return NULL.
+ * put_swap_device() is called.  Return NULL for an empty entry or a
+ * device that is going away, and ERR_PTR(-EIO) if the entry's type
+ * names no swap device or its offset is past the end of one. These EIOs
+ * are preceded by pr_err().
  *
  * Notice that swapoff or swapoff+swapon can still happen before the
  * percpu_ref_tryget_live() in get_swap_device() or after the
@@ -1900,12 +1903,13 @@ struct swap_info_struct *get_swap_device(swp_entry_t entry)
 	return si;
 bad_nofile:
 	pr_err("%s: %s%08lx\n", __func__, Bad_file, entry.val);
+	return ERR_PTR(-EIO);
 out:
 	return NULL;
 put_out:
 	pr_err("%s: %s%08lx\n", __func__, Bad_offset, entry.val);
 	percpu_ref_put(&si->users);
-	return NULL;
+	return ERR_PTR(-EIO);
 }
 
 /*
@@ -2001,7 +2005,7 @@ int swp_swapcount(swp_entry_t entry)
 	int count;
 
 	si = get_swap_device(entry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return 0;
 
 	ci = swap_cluster_lock(si, swp_offset(entry));
@@ -2127,7 +2131,7 @@ void swap_put_entries_direct(swp_entry_t entry, int nr)
 	struct swap_info_struct *si;
 
 	si = get_swap_device(entry);
-	if (WARN_ON_ONCE(!si))
+	if (WARN_ON_ONCE(IS_ERR_OR_NULL(si)))
 		return;
 	if (WARN_ON_ONCE(end_offset > si->max))
 		goto out;
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 23fb68fce000e..878e27f571638 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1700,7 +1700,7 @@ static long move_pages_ptes(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd
 		}
 
 		si = get_swap_device(entry);
-		if (unlikely(!si)) {
+		if (IS_ERR_OR_NULL(si)) {
 			ret = -EAGAIN;
 			goto out;
 		}
@@ -1757,7 +1757,7 @@ static long move_pages_ptes(struct mm_struct *mm, pmd_t *dst_pmd, pmd_t *src_pmd
 	if (dst_pte)
 		pte_unmap(dst_pte);
 	mmu_notifier_invalidate_range_end(&range);
-	if (si)
+	if (!IS_ERR_OR_NULL(si))
 		put_swap_device(si);
 
 	return ret;
diff --git a/mm/zswap.c b/mm/zswap.c
index 37f34e406c8e3..1d11f350ac1e1 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -997,7 +997,7 @@ static int zswap_writeback_entry(struct zswap_entry *entry,
 
 	/* try to allocate swap cache folio */
 	si = get_swap_device(swpentry);
-	if (!si)
+	if (IS_ERR_OR_NULL(si))
 		return -EEXIST;
 
 	mpol = get_task_policy(current);

gemini-3.1-pro-preview

null

null

							input: 4189
							output: 186
							thoughts: 341
						

**My Assessment of the Swap Device Return Value Patch**

Okay, so this patch is tweaking how `get_swap_device()` behaves, specifically regarding its return values. Previously, a `NULL` return signaled failure. Now, it can return either `ERR_PTR(-EIO)` for problematic entries, or still `NULL` for empty or disappearing devices. The calling code has been updated to use `IS_ERR_OR_NULL(si)` instead of the old `!si` check. Critically, in `do_swap_page`, if `IS_ERR(si)` evaluates to true, it sets `ret = VM_FAULT_SIGBUS`.

Essentially, this is a modification to the swap handling memory management. It's a control flow change related to error handling, ensuring that bad swap entries don't get silently ignored and potentially cause bigger problems. Instead, we now get a `VM_FAULT_SIGBUS`, which is the correct response in this situation. It's much better than silently ignoring the errors.

My immediate impression is that there's no exposure of uninitialized memory to user space here. The patch doesn't introduce any new data structures or fields, nor does it appear to be working with any uninitialized memory. The function `get_swap_device()` returns a pointer to a `struct swap_info_struct`, which is now an error pointer in some situations, but the callers are adapted to handle this. It seems like a logic fix to improve the robustness of the swap subsystem. Standard bug detectors like KASAN are entirely sufficient for this kind of change. There's no reason to consider KMSAN here because there are no new allocations or potential for uninitialized memory use that would require it.

Therefore, I'm confident in setting `NeedsKMSAN=false`. The reasoning is straightforward: this patch is a control flow change with no risk of uninitialized memory.

{
  "KMSANReasoning": "The patch modifies the error handling of `get_swap_device()` to return `ERR_PTR(-EIO)` for bad swap entries instead of just `NULL`, and updates all callers to check for `IS_ERR_OR_NULL(si)`. In `do_swap_page()`, it translates the error into a `VM_FAULT_SIGBUS`. These changes are purely related to control flow and error propagation in the memory management subsystem (swap handling). They do not introduce any new allocations, do not expose kernel structures to user space, and do not involve any uninitialized memory risks. Therefore, a dedicated KMSAN fuzzing session is not necessary, as standard KASAN and other bug detectors are sufficient to catch any potential memory corruption or logic bugs in this area.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch modifies the error handling of `get_swap_device()` to return `ERR_PTR(-EIO)` for bad swap entries instead of just `NULL`, and updates all callers to check for `IS_ERR_OR_NULL(si)`. In `do_swap_page()`, it translates the error into a `VM_FAULT_SIGBUS`. These changes are purely related to control flow and error propagation in the memory management subsystem (swap handling). They do not introduce any new allocations, do not expose kernel structures to user space, and do not involve any uninitialized memory risks. Therefore, a dedicated KMSAN fuzzing session is not necessary, as standard KASAN and other bug detectors are sufficient to catch any potential memory corruption or logic bugs in this area.",
  "NeedsKMSAN": false
}