AI Trajectory

null

{
  "EnableConfigs": [
    "MEMORY_FAILURE",
    "KEXEC",
    "KEXEC_FILE"
  ],
  "FocusSymbols": [
    "sanity_check_segment_list",
    "kexec_locate_mem_hole",
    "range_first_hwpoison",
    "range_last_hwpoison"
  ],
  "KMSANReasoning": "The patch adds checks to avoid hardware-poisoned memory during kexec segment allocation and validation. It modifies memory allocation logic to skip poisoned pages and rejects kexec segments that land on poisoned memory. It does not introduce new data structures copied to user space, nor does it leave any variables or struct fields uninitialized. There is no risk of uninitialized memory usage or info-leaks, so a dedicated KMSAN session is not required. Standard KASAN and other bug detectors are sufficient.",
  "NeedsKMSAN": false,
  "Reasoning": "The patch modifies the kexec subsystem to avoid allocating memory on hardware-poisoned pages. This is a functional change in core kernel logic that can be reached via the kexec_load and kexec_file_load syscalls.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit a863f6ac5b5b61708020b3bc343342ad7ae506cc\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Wed Aug 12 11:57:06 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/include/linux/mm.h b/include/linux/mm.h\nindex 13902368471e1..ff83ae7a7efe6 100644\n--- a/include/linux/mm.h\n+++ b/include/linux/mm.h\n@@ -5252,6 +5252,8 @@ extern const struct attribute_group memory_failure_attr_group;\n extern void memory_failure_queue(unsigned long pfn, int flags);\n void num_poisoned_pages_inc(unsigned long pfn);\n void num_poisoned_pages_sub(unsigned long pfn, long i);\n+phys_addr_t range_first_hwpoison(phys_addr_t start, unsigned long size);\n+phys_addr_t range_last_hwpoison(phys_addr_t start, unsigned long size);\n #else\n static inline void memory_failure_queue(unsigned long pfn, int flags)\n {\n@@ -5264,6 +5266,18 @@ static inline void num_poisoned_pages_inc(unsigned long pfn)\n static inline void num_poisoned_pages_sub(unsigned long pfn, long i)\n {\n }\n+\n+static inline phys_addr_t range_first_hwpoison(phys_addr_t start,\n+\t\t\t\t\t       unsigned long size)\n+{\n+\treturn PHYS_ADDR_MAX;\n+}\n+\n+static inline phys_addr_t range_last_hwpoison(phys_addr_t start,\n+\t\t\t\t\t      unsigned long size)\n+{\n+\treturn PHYS_ADDR_MAX;\n+}\n #endif\n \n #if defined(CONFIG_MEMORY_FAILURE) \u0026\u0026 defined(CONFIG_MEMORY_HOTPLUG)\ndiff --git a/kernel/kexec_core.c b/kernel/kexec_core.c\nindex dc770b9a6d053..7ee8c9f078f6b 100644\n--- a/kernel/kexec_core.c\n+++ b/kernel/kexec_core.c\n@@ -212,6 +212,16 @@ int sanity_check_segment_list(struct kimage *image)\n \t}\n #endif\n \n+\t/*\n+\t * Reject destinations that land on hardware-poisoned memory: the\n+\t * relocation copy would machine-check on the bad frame.\n+\t */\n+\tfor (i = 0; i \u003c nr_segments; i++) {\n+\t\tif (range_first_hwpoison(image-\u003esegment[i].mem,\n+\t\t\t\t\t image-\u003esegment[i].memsz) != PHYS_ADDR_MAX)\n+\t\t\treturn -EHWPOISON;\n+\t}\n+\n \t/*\n \t * The destination addresses are searched from system RAM rather than\n \t * being allocated from the buddy allocator, so they are not guaranteed\ndiff --git a/kernel/kexec_file.c b/kernel/kexec_file.c\nindex 2bfbb2d144e69..527fd805a3a6b 100644\n--- a/kernel/kexec_file.c\n+++ b/kernel/kexec_file.c\n@@ -474,6 +474,7 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,\n {\n \tstruct kimage *image = kbuf-\u003eimage;\n \tunsigned long temp_start, temp_end;\n+\tphys_addr_t poison;\n \n \ttemp_end = min(end, kbuf-\u003ebuf_max);\n \ttemp_start = temp_end - kbuf-\u003ememsz + 1;\n@@ -483,7 +484,9 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,\n \t\t/* align down start */\n \t\ttemp_start = ALIGN_DOWN(temp_start, kbuf-\u003ebuf_align);\n \n-\t\tif (temp_start \u003c start || temp_start \u003c kbuf-\u003ebuf_min)\n+\t\t/* A candidate above the range means the walk wrapped around */\n+\t\tif (temp_start \u003c start || temp_start \u003c kbuf-\u003ebuf_min ||\n+\t\t    temp_start \u003e end)\n \t\t\treturn 0;\n \n \t\ttemp_end = temp_start + kbuf-\u003ememsz - 1;\n@@ -503,6 +506,13 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,\n \t\t\tcontinue;\n \t\t}\n \n+\t\tpoison = range_first_hwpoison(temp_start, kbuf-\u003ememsz);\n+\t\tif (poison != PHYS_ADDR_MAX) {\n+\t\t\t/* we hit a poisoned page */\n+\t\t\ttemp_start = poison - kbuf-\u003ememsz;\n+\t\t\tcontinue;\n+\t\t}\n+\n \t\t/* We found a suitable memory range */\n \t\tbreak;\n \t} while (1);\n@@ -519,6 +529,7 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,\n {\n \tstruct kimage *image = kbuf-\u003eimage;\n \tunsigned long temp_start, temp_end;\n+\tphys_addr_t poison;\n \n \ttemp_start = max(start, kbuf-\u003ebuf_min);\n \n@@ -545,6 +556,13 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,\n \t\t\tcontinue;\n \t\t}\n \n+\t\tpoison = range_last_hwpoison(temp_start, kbuf-\u003ememsz);\n+\t\tif (poison != PHYS_ADDR_MAX) {\n+\t\t\t/* we hit a poisoned page */\n+\t\t\ttemp_start = poison + PAGE_SIZE;\n+\t\t\tcontinue;\n+\t\t}\n+\n \t\t/* We found a suitable memory range */\n \t\tbreak;\n \t} while (1);\ndiff --git a/mm/memory-failure.c b/mm/memory-failure.c\nindex a8b03e2920ba8..a2ca8df501cae 100644\n--- a/mm/memory-failure.c\n+++ b/mm/memory-failure.c\n@@ -96,6 +96,46 @@ void num_poisoned_pages_sub(unsigned long pfn, long i)\n \t\tmemblk_nr_poison_sub(pfn, i);\n }\n \n+/*\n+ * Return the first or the last hardware-poisoned online page in [start,\n+ * start + size), or PHYS_ADDR_MAX if the range is clean.\n+ */\n+static phys_addr_t range_hwpoison(phys_addr_t start, unsigned long size,\n+\t\t\t\t  bool first)\n+{\n+\tphys_addr_t poison = PHYS_ADDR_MAX;\n+\tunsigned long pfn, end_pfn;\n+\n+\tif (!size || !atomic_long_read(\u0026num_poisoned_pages))\n+\t\treturn poison;\n+\n+\tend_pfn = PHYS_PFN(start + size - 1);\n+\tfor (pfn = PHYS_PFN(start); pfn \u003c= end_pfn; pfn++) {\n+\t\tstruct page *page = pfn_to_online_page(pfn);\n+\n+\t\tif (page \u0026\u0026 is_page_hwpoison(page)) {\n+\t\t\tif (first)\n+\t\t\t\treturn PFN_PHYS(pfn);\n+\n+\t\t\tpoison = PFN_PHYS(pfn);\n+\t\t}\n+\n+\t\tcond_resched();\n+\t}\n+\n+\treturn poison;\n+}\n+\n+phys_addr_t range_first_hwpoison(phys_addr_t start, unsigned long size)\n+{\n+\treturn range_hwpoison(start, size, true);\n+}\n+\n+phys_addr_t range_last_hwpoison(phys_addr_t start, unsigned long size)\n+{\n+\treturn range_hwpoison(start, size, false);\n+}\n+\n /**\n  * MF_ATTR_RO - Create sysfs entry for each memory failure statistics.\n  * @_name: name of the file in the per NUMA sysfs directory.\n"
}

best-expensive

null

{
  "EnableConfigs": [
    "MEMORY_FAILURE",
    "KEXEC",
    "KEXEC_FILE"
  ],
  "FocusSymbols": [
    "sanity_check_segment_list",
    "kexec_locate_mem_hole",
    "range_first_hwpoison",
    "range_last_hwpoison"
  ],
  "Reasoning": "The patch modifies the kexec subsystem to avoid allocating memory on hardware-poisoned pages. This is a functional change in core kernel logic that can be reached via the kexec_load and kexec_file_load syscalls.",
  "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 a863f6ac5b5b61708020b3bc343342ad7ae506cc
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Aug 12 11:57:06 2026 +0000

    syz-cluster: applied patch under review

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 13902368471e1..ff83ae7a7efe6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -5252,6 +5252,8 @@ extern const struct attribute_group memory_failure_attr_group;
 extern void memory_failure_queue(unsigned long pfn, int flags);
 void num_poisoned_pages_inc(unsigned long pfn);
 void num_poisoned_pages_sub(unsigned long pfn, long i);
+phys_addr_t range_first_hwpoison(phys_addr_t start, unsigned long size);
+phys_addr_t range_last_hwpoison(phys_addr_t start, unsigned long size);
 #else
 static inline void memory_failure_queue(unsigned long pfn, int flags)
 {
@@ -5264,6 +5266,18 @@ static inline void num_poisoned_pages_inc(unsigned long pfn)
 static inline void num_poisoned_pages_sub(unsigned long pfn, long i)
 {
 }
+
+static inline phys_addr_t range_first_hwpoison(phys_addr_t start,
+					       unsigned long size)
+{
+	return PHYS_ADDR_MAX;
+}
+
+static inline phys_addr_t range_last_hwpoison(phys_addr_t start,
+					      unsigned long size)
+{
+	return PHYS_ADDR_MAX;
+}
 #endif
 
 #if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_MEMORY_HOTPLUG)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index dc770b9a6d053..7ee8c9f078f6b 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -212,6 +212,16 @@ int sanity_check_segment_list(struct kimage *image)
 	}
 #endif
 
+	/*
+	 * Reject destinations that land on hardware-poisoned memory: the
+	 * relocation copy would machine-check on the bad frame.
+	 */
+	for (i = 0; i < nr_segments; i++) {
+		if (range_first_hwpoison(image->segment[i].mem,
+					 image->segment[i].memsz) != PHYS_ADDR_MAX)
+			return -EHWPOISON;
+	}
+
 	/*
 	 * The destination addresses are searched from system RAM rather than
 	 * being allocated from the buddy allocator, so they are not guaranteed
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 2bfbb2d144e69..527fd805a3a6b 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -474,6 +474,7 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
 {
 	struct kimage *image = kbuf->image;
 	unsigned long temp_start, temp_end;
+	phys_addr_t poison;
 
 	temp_end = min(end, kbuf->buf_max);
 	temp_start = temp_end - kbuf->memsz + 1;
@@ -483,7 +484,9 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
 		/* align down start */
 		temp_start = ALIGN_DOWN(temp_start, kbuf->buf_align);
 
-		if (temp_start < start || temp_start < kbuf->buf_min)
+		/* A candidate above the range means the walk wrapped around */
+		if (temp_start < start || temp_start < kbuf->buf_min ||
+		    temp_start > end)
 			return 0;
 
 		temp_end = temp_start + kbuf->memsz - 1;
@@ -503,6 +506,13 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
 			continue;
 		}
 
+		poison = range_first_hwpoison(temp_start, kbuf->memsz);
+		if (poison != PHYS_ADDR_MAX) {
+			/* we hit a poisoned page */
+			temp_start = poison - kbuf->memsz;
+			continue;
+		}
+
 		/* We found a suitable memory range */
 		break;
 	} while (1);
@@ -519,6 +529,7 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
 {
 	struct kimage *image = kbuf->image;
 	unsigned long temp_start, temp_end;
+	phys_addr_t poison;
 
 	temp_start = max(start, kbuf->buf_min);
 
@@ -545,6 +556,13 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
 			continue;
 		}
 
+		poison = range_last_hwpoison(temp_start, kbuf->memsz);
+		if (poison != PHYS_ADDR_MAX) {
+			/* we hit a poisoned page */
+			temp_start = poison + PAGE_SIZE;
+			continue;
+		}
+
 		/* We found a suitable memory range */
 		break;
 	} while (1);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index a8b03e2920ba8..a2ca8df501cae 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -96,6 +96,46 @@ void num_poisoned_pages_sub(unsigned long pfn, long i)
 		memblk_nr_poison_sub(pfn, i);
 }
 
+/*
+ * Return the first or the last hardware-poisoned online page in [start,
+ * start + size), or PHYS_ADDR_MAX if the range is clean.
+ */
+static phys_addr_t range_hwpoison(phys_addr_t start, unsigned long size,
+				  bool first)
+{
+	phys_addr_t poison = PHYS_ADDR_MAX;
+	unsigned long pfn, end_pfn;
+
+	if (!size || !atomic_long_read(&num_poisoned_pages))
+		return poison;
+
+	end_pfn = PHYS_PFN(start + size - 1);
+	for (pfn = PHYS_PFN(start); pfn <= end_pfn; pfn++) {
+		struct page *page = pfn_to_online_page(pfn);
+
+		if (page && is_page_hwpoison(page)) {
+			if (first)
+				return PFN_PHYS(pfn);
+
+			poison = PFN_PHYS(pfn);
+		}
+
+		cond_resched();
+	}
+
+	return poison;
+}
+
+phys_addr_t range_first_hwpoison(phys_addr_t start, unsigned long size)
+{
+	return range_hwpoison(start, size, true);
+}
+
+phys_addr_t range_last_hwpoison(phys_addr_t start, unsigned long size)
+{
+	return range_hwpoison(start, size, false);
+}
+
 /**
  * MF_ATTR_RO - Create sysfs entry for each memory failure statistics.
  * @_name: name of the file in the per NUMA sysfs directory.

gemini-3.1-pro-preview

null

null

							input: 3757
							output: 37
							thoughts: 463
						

**Fuzzing Candidate Evaluation: Kernel Patch Series**

Okay, so I've been given a patch series and I need to determine if it introduces functional changes that warrant fuzzing. Let's break this down. From what I see, this patch modifies `include/linux/mm.h`, `kernel/kexec_core.c`, `kernel/kexec_file.c`, and `mm/memory-failure.c`. That's a decent spread, indicating changes in both kexec and memory failure handling – critical areas, definitely.

Specifically, it looks like the changes are centered around how kexec interacts with and handles hardware-poisoned memory. The patch adds checks in `sanity_check_segment_list`, preventing kexec segments from being loaded into poisoned memory, and modifies memory allocation within kexec using `locate_mem_hole_top_down` and `locate_mem_hole_bottom_up` to skip over these poisoned regions. The `mm/memory-failure.c` additions look like the core implementation of the poisoning range mechanisms.

Given that it touches the kexec subsystem and memory failure, this is definitely worth fuzzing. The question now becomes: What functions should we target? I need to identify the relevant `FocusSymbols`. Let's see:

*   `sanity_check_segment_list` is a strong candidate, as it is a central check, rejecting poisoned memory.

*   `locate_mem_hole_top_down` and `locate_mem_hole_bottom_up` are good, but I remember, or should quickly check, the prompt says to prefer non-static, non-inlined API entrypoint functions over internal static helper functions.

*   Checking `locate_mem_hole_top_down` and `locate_mem_hole_bottom_up`, oh yeah, these are `static` functions, so they are not directly exposed and used. I will look for calls to these functions to identify entrypoints.

So, I will look for the call sites to those functions.

{
  "Expression": "locate_mem_hole_top_down",
  "PathPrefix": "kernel/kexec_file.c"
}

{
  "Output": "kernel/kexec_file.c=364=SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,\n--\nkernel/kexec_file.c-471-\nkernel/kexec_file.c:472:static int locate_mem_hole_top_down(unsigned long start, unsigned long end,\nkernel/kexec_file.c-473-\t\t\t\t    struct kexec_buf *kbuf)\n--\nkernel/kexec_file.c=577=static int locate_mem_hole_callback(struct resource *res, void *arg)\n--\nkernel/kexec_file.c-599-\tif (kbuf-\u003etop_down)\nkernel/kexec_file.c:600:\t\treturn locate_mem_hole_top_down(start, end, kbuf);\nkernel/kexec_file.c-601-\treturn locate_mem_hole_bottom_up(start, end, kbuf);\n"
}

gemini-3.1-pro-preview

null

null

							input: 4945
							output: 35
							thoughts: 20
						

Here's a summary of my thought process:

**Tracing the Source of `locate_mem_hole_callback`**

Okay, `locate_mem_hole_callback` has been invoked. My first thought is: *Where* did this call originate? I need to quickly identify the calling function or functions. Understanding the context of this call is crucial. Knowing the caller will tell me a great deal about why it was called and what's going on. I'll need to use my usual debugging tools and strategies to trace back the execution path. Time to dive into the codebase and start the hunt!

{
  "Expression": "locate_mem_hole_callback",
  "PathPrefix": "kernel/kexec_file.c"
}

{
  "Output": "kernel/kexec_file.c=527=static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,\n--\nkernel/kexec_file.c-576-\nkernel/kexec_file.c:577:static int locate_mem_hole_callback(struct resource *res, void *arg)\nkernel/kexec_file.c-578-{\n--\nkernel/kexec_file.c=605=static int kexec_walk_memblock(struct kexec_buf *kbuf,\n--\nkernel/kexec_file.c-620-\t * IORESOURCE_SYSRAM_DRIVER_MANAGED handling in\nkernel/kexec_file.c:621:\t * locate_mem_hole_callback().\nkernel/kexec_file.c-622-\t */\n--\nkernel/kexec_file.c=733=int kexec_locate_mem_hole(struct kexec_buf *kbuf)\n--\nkernel/kexec_file.c-744-\t */\nkernel/kexec_file.c:745:\tret = kho_locate_mem_hole(kbuf, locate_mem_hole_callback);\nkernel/kexec_file.c-746-\tif (ret \u003c= 0)\n--\nkernel/kexec_file.c-756-\tif (!IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))\nkernel/kexec_file.c:757:\t\tret = kexec_walk_resources(kbuf, locate_mem_hole_callback);\nkernel/kexec_file.c-758-\telse\nkernel/kexec_file.c:759:\t\tret = kexec_walk_memblock(kbuf, locate_mem_hole_callback);\nkernel/kexec_file.c-760-\n"
}

gemini-3.1-pro-preview

null

null

							input: 5586
							output: 35
							thoughts: 30
						

Okay, here's my interpretation of that thought process, from an expert's perspective:

**Diving into the Kernel's Boot Process**

Alright, the debugging has led me to `kexec_locate_mem_hole`. This is where the magic begins, the entry point for memory hole detection in this kexec implementation. Now, before I even start to understand the memory allocation, I need to make sure the foundational data structures are in order. My immediate next step is to examine the `sanity_check_segment_list`. I need to ensure the segment list is coherent before trusting the rest of the logic. Garbage in, garbage out, as they say! It's likely this function will be checking for overlaps, invalid addresses, or other structural problems in the memory map used by kexec. A bad segment list will throw a wrench into everything, potentially leading to a crash later. So, I need to verify its integrity first.

{
  "Expression": "sanity_check_segment_list",
  "PathPrefix": "kernel/kexec_core.c"
}

{
  "Output": "kernel/kexec_core.c=106=static struct page *kimage_alloc_page(struct kimage *image,\n--\nkernel/kexec_core.c-109-\nkernel/kexec_core.c:110:int sanity_check_segment_list(struct kimage *image)\nkernel/kexec_core.c-111-{\n"
}

gemini-3.1-pro-preview

null

null

							input: 5949
							output: 29
							thoughts: 13
						

Here's my thought process, summarized as you requested:

**Tracing the Call Stack for `sanity_check_segment_list`**

Okay, so I need to understand the execution context of `sanity_check_segment_list`. My initial instinct is to determine its upstream dependencies. I'm thinking, where is this function actually *called*? Knowing that will provide crucial insight into its purpose and how it's used within the broader system. I need to quickly trace the call stack to see what functions invoke it. I'm looking for the immediate callers, and then potentially their callers, and so on, to build a mental map of its role. This is the first step in debugging or understanding the impact of any changes to this segment. I'll need to use some tools or good old-fashioned code diving to quickly find all instances of `sanity_check_segment_list`.

{
  "Expression": "sanity_check_segment_list",
  "PathPrefix": "kernel/"
}

{
  "Output": "kernel/kexec.c=22=static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,\n--\nkernel/kexec.c-56-\nkernel/kexec.c:57:\tret = sanity_check_segment_list(image);\nkernel/kexec.c-58-\tif (ret)\n--\nkernel/kexec_core.c=106=static struct page *kimage_alloc_page(struct kimage *image,\n--\nkernel/kexec_core.c-109-\nkernel/kexec_core.c:110:int sanity_check_segment_list(struct kimage *image)\nkernel/kexec_core.c-111-{\n--\nkernel/kexec_file.c=305=kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,\n--\nkernel/kexec_file.c-332-\nkernel/kexec_file.c:333:\tret = sanity_check_segment_list(image);\nkernel/kexec_file.c-334-\tif (ret)\n--\nkernel/kexec_internal.h=9=struct kimage *do_kimage_alloc_init(void);\nkernel/kexec_internal.h:10:int sanity_check_segment_list(struct kimage *image);\nkernel/kexec_internal.h-11-void kimage_free_page_list(struct list_head *list);\n"
}

gemini-3.1-pro-preview

null

null

							input: 6551
							output: 26
							thoughts: 165
						

**My Initial Investigation into `kexec` and Memory Failure Handling**

Okay, so I'm diving into this `kexec` load process. From what I can see, `kimage_alloc_init` and `kimage_file_alloc_init` are the key entry points, specifically called from `sys_kexec_load` and `sys_kexec_file_load`. This immediately tells me that `sanity_check_segment_list` is a prime candidate for focused analysis within the code. Then I also should look into `kexec_locate_mem_hole`.

Furthermore, I should be looking at `range_first_hwpoison` and `range_last_hwpoison`. They're exported functions residing in `mm/memory-failure.c`, which likely means they're core to the memory-failure handling.

Now, before I dig deeper, I need to understand the configuration context. This patch touches `mm/memory-failure.c`. That file's compilation is gated by `CONFIG_MEMORY_FAILURE`. I should confirm that option's status. I'll need to check `mm/Makefile` to confirm the dependencies for that flag.

{
  "Expression": "memory-failure",
  "PathPrefix": "mm/Makefile"
}

{
  "Output": "mm/Makefile=111=obj-$(CONFIG_DMAPOOL_TEST) += dmapool_test.o\nmm/Makefile:112:obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o\nmm/Makefile-113-obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o\n"
}

gemini-3.1-pro-preview

null

null

							input: 7086
							output: 25
							thoughts: 63
						

**Examining the Kernel Build Configuration**

Okay, so I see that `CONFIG_MEMORY_FAILURE` is definitely a prerequisite here. That's good to keep in mind. Also, I'm noting that both `kexec_core.c` and `kexec_file.c` are only compiled when `CONFIG_KEXEC_CORE` and `CONFIG_KEXEC_FILE` are actually *enabled* in the kernel config. Just a quick sanity check to ensure the build dependencies are all in line. Given this, I should probably take a look at the kernel's `Makefile` to confirm the dependencies and build rules. Let's see what we've got in there.

{
  "Expression": "kexec",
  "PathPrefix": "kernel/Makefile"
}

{
  "Output": "kernel/Makefile=80=obj-$(CONFIG_CRASH_RESERVE) += crash_reserve.o\nkernel/Makefile:81:obj-$(CONFIG_KEXEC_CORE) += kexec_core.o\nkernel/Makefile-82-obj-$(CONFIG_CRASH_DUMP) += crash_core.o\n--\nkernel/Makefile=84=obj-$(CONFIG_CRASH_DUMP_KUNIT_TEST) += crash_core_test.o\nkernel/Makefile:85:obj-$(CONFIG_KEXEC) += kexec.o\nkernel/Makefile:86:obj-$(CONFIG_KEXEC_FILE) += kexec_file.o\nkernel/Makefile:87:obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o\nkernel/Makefile-88-obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o\n"
}

gemini-3.1-pro-preview

null

null

							input: 7540
							output: 29
							thoughts: 35
						

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

**Kernel Configuration Dependencies Assessment**

Alright, so the core of this kexec functionality, the fundamentals – `CONFIG_KEXEC_CORE` and `CONFIG_KEXEC_FILE` – those are a given. No surprises there. But before I go too far down this road, I'm thinking, let's take a closer look at the dependencies associated with `CONFIG_MEMORY_FAILURE`. It's pretty crucial to understand how that interacts with the overall kexec architecture, especially if we're dealing with potentially problematic memory situations. Gotta be proactive about that potential impact, right? Need to get a grasp of that impact to prevent some headache down the line.

{
  "Expression": "config MEMORY_FAILURE",
  "PathPrefix": "mm/Kconfig"
}

{
  "Output": "mm/Kconfig=762=config ARCH_SUPPORTS_MEMORY_FAILURE\n--\nmm/Kconfig-764-\nmm/Kconfig:765:config MEMORY_FAILURE\nmm/Kconfig-766-\tdepends on MMU\n"
}

gemini-3.1-pro-preview

null

null

							input: 7833
							output: 30
							thoughts: 21
						

Here's my summary, as the thought process unfolds:

**Dependencies, Dependencies, Dependencies!**

Okay, time to dive into this. First things first: `CONFIG_KEXEC` and `CONFIG_KEXEC_FILE`. I need to figure out how these are related, and more importantly, what they depend on. I know the general area, but I need to make sure I'm not overlooking any subtle build configuration interactions. Let's see... I'll need to double check the configuration options and their associated documentation to ensure proper settings for the feature.

{
  "Expression": "config KEXEC",
  "PathPrefix": "kernel/Kconfig.kexec"
}

{
  "Output": "kernel/Kconfig.kexec=8=config VMCORE_INFO\n--\nkernel/Kconfig.kexec-10-\nkernel/Kconfig.kexec:11:config KEXEC_CORE\nkernel/Kconfig.kexec-12-\tbool\nkernel/Kconfig.kexec-13-\nkernel/Kconfig.kexec:14:config KEXEC_ELF\nkernel/Kconfig.kexec-15-\tbool\n--\nkernel/Kconfig.kexec=17=config HAVE_IMA_KEXEC\n--\nkernel/Kconfig.kexec-19-\nkernel/Kconfig.kexec:20:config KEXEC\nkernel/Kconfig.kexec-21-\tbool \"Enable kexec system call\"\n--\nkernel/Kconfig.kexec-37-\nkernel/Kconfig.kexec:38:config KEXEC_FILE\nkernel/Kconfig.kexec-39-\tbool \"Enable kexec file based system call\"\n--\nkernel/Kconfig.kexec-48-\nkernel/Kconfig.kexec:49:config KEXEC_SIG\nkernel/Kconfig.kexec-50-\tbool \"Verify kernel signature during kexec_file_load() syscall\"\n--\nkernel/Kconfig.kexec-62-\nkernel/Kconfig.kexec:63:config KEXEC_SIG_FORCE\nkernel/Kconfig.kexec-64-\tbool \"Require a valid signature in kexec_file_load() syscall\"\n--\nkernel/Kconfig.kexec-70-\nkernel/Kconfig.kexec:71:config KEXEC_IMAGE_VERIFY_SIG\nkernel/Kconfig.kexec-72-\tbool \"Enable Image signature verification support (ARM)\"\n--\nkernel/Kconfig.kexec-79-\nkernel/Kconfig.kexec:80:config KEXEC_BZIMAGE_VERIFY_SIG\nkernel/Kconfig.kexec-81-\tbool \"Enable bzImage signature verification support\"\n--\nkernel/Kconfig.kexec-88-\nkernel/Kconfig.kexec:89:config KEXEC_JUMP\nkernel/Kconfig.kexec-90-\tbool \"kexec jump\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 8535
							output: 133
							thoughts: 483
						

**My Analysis of This Kernel Patch**

Okay, so I've broken this patch down. We're dealing with a change within the `kexec` subsystem, specifically aiming to prevent memory allocation on hardware-poisoned pages. This has implications for how the kernel handles crashes and restarts.

First, the core elements. I've identified the configurations we'll need to enable: `MEMORY_FAILURE`, `KEXEC`, and `KEXEC_FILE`. `MEMORY_FAILURE` is contingent on `MMU` and `ARCH_SUPPORTS_MEMORY_FAILURE`, which is expected. The other two are fairly standard for kexec on supported architectures.

Now for the focus symbols, these are key functions this patch touches. I've verified my choices: `kexec_locate_mem_hole`, it seems, is the correct function as `locate_mem_hole_top_down` and `locate_mem_hole_bottom_up` are called and are used by `kexec_locate_mem_hole`. Good. Then, `range_first_hwpoison` and `range_last_hwpoison` are good focus symbols as they are not static, and have been declared in `include/linux/mm.h` and defined in `mm/memory-failure.c`. Same case for `sanity_check_segment_list`, which is defined in `kernel/kexec_core.c` and declared in `kernel/kexec_internal.h`.

Essentially, this patch modifies fundamental kernel logic. The `kexec_load` and `kexec_file_load` syscalls are relevant.

So my assessment:

*   **WorthFuzzing:** True
*   **Reasoning:** This is a functional change related to poisoned pages within the `kexec` subsystem. It touches core kernel logic accessible via syscalls.
*   **FocusSymbols:** `sanity_check_segment_list`, `kexec_locate_mem_hole`, `range_first_hwpoison`, `range_last_hwpoison`
*   **EnableConfigs:** `MEMORY_FAILURE`, `KEXEC`, `KEXEC_FILE`

I'm ready to use the set-results tool now.

{
  "EnableConfigs": [
    "MEMORY_FAILURE",
    "KEXEC",
    "KEXEC_FILE"
  ],
  "FocusSymbols": [
    "sanity_check_segment_list",
    "kexec_locate_mem_hole",
    "range_first_hwpoison",
    "range_last_hwpoison"
  ],
  "Reasoning": "The patch modifies the kexec subsystem to avoid allocating memory on hardware-poisoned pages. This is a functional change in core kernel logic that can be reached via the kexec_load and kexec_file_load syscalls.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "MEMORY_FAILURE",
    "KEXEC",
    "KEXEC_FILE"
  ],
  "FocusSymbols": [
    "sanity_check_segment_list",
    "kexec_locate_mem_hole",
    "range_first_hwpoison",
    "range_last_hwpoison"
  ],
  "Reasoning": "The patch modifies the kexec subsystem to avoid allocating memory on hardware-poisoned pages. This is a functional change in core kernel logic that can be reached via the kexec_load and kexec_file_load syscalls.",
  "WorthFuzzing": true
}

{
  "WorthFuzzing": true
}

null

best-expensive

null

{
  "KMSANReasoning": "The patch adds checks to avoid hardware-poisoned memory during kexec segment allocation and validation. It modifies memory allocation logic to skip poisoned pages and rejects kexec segments that land on poisoned memory. It does not introduce new data structures copied to user space, nor does it leave any variables or struct fields uninitialized. There is no risk of uninitialized memory usage or info-leaks, so a dedicated KMSAN session is not required. Standard KASAN and other bug detectors are sufficient.",
  "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 a863f6ac5b5b61708020b3bc343342ad7ae506cc
Author: syz-cluster <triage@syzkaller.com>
Date:   Wed Aug 12 11:57:06 2026 +0000

    syz-cluster: applied patch under review

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 13902368471e1..ff83ae7a7efe6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -5252,6 +5252,8 @@ extern const struct attribute_group memory_failure_attr_group;
 extern void memory_failure_queue(unsigned long pfn, int flags);
 void num_poisoned_pages_inc(unsigned long pfn);
 void num_poisoned_pages_sub(unsigned long pfn, long i);
+phys_addr_t range_first_hwpoison(phys_addr_t start, unsigned long size);
+phys_addr_t range_last_hwpoison(phys_addr_t start, unsigned long size);
 #else
 static inline void memory_failure_queue(unsigned long pfn, int flags)
 {
@@ -5264,6 +5266,18 @@ static inline void num_poisoned_pages_inc(unsigned long pfn)
 static inline void num_poisoned_pages_sub(unsigned long pfn, long i)
 {
 }
+
+static inline phys_addr_t range_first_hwpoison(phys_addr_t start,
+					       unsigned long size)
+{
+	return PHYS_ADDR_MAX;
+}
+
+static inline phys_addr_t range_last_hwpoison(phys_addr_t start,
+					      unsigned long size)
+{
+	return PHYS_ADDR_MAX;
+}
 #endif
 
 #if defined(CONFIG_MEMORY_FAILURE) && defined(CONFIG_MEMORY_HOTPLUG)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index dc770b9a6d053..7ee8c9f078f6b 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -212,6 +212,16 @@ int sanity_check_segment_list(struct kimage *image)
 	}
 #endif
 
+	/*
+	 * Reject destinations that land on hardware-poisoned memory: the
+	 * relocation copy would machine-check on the bad frame.
+	 */
+	for (i = 0; i < nr_segments; i++) {
+		if (range_first_hwpoison(image->segment[i].mem,
+					 image->segment[i].memsz) != PHYS_ADDR_MAX)
+			return -EHWPOISON;
+	}
+
 	/*
 	 * The destination addresses are searched from system RAM rather than
 	 * being allocated from the buddy allocator, so they are not guaranteed
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 2bfbb2d144e69..527fd805a3a6b 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -474,6 +474,7 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
 {
 	struct kimage *image = kbuf->image;
 	unsigned long temp_start, temp_end;
+	phys_addr_t poison;
 
 	temp_end = min(end, kbuf->buf_max);
 	temp_start = temp_end - kbuf->memsz + 1;
@@ -483,7 +484,9 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
 		/* align down start */
 		temp_start = ALIGN_DOWN(temp_start, kbuf->buf_align);
 
-		if (temp_start < start || temp_start < kbuf->buf_min)
+		/* A candidate above the range means the walk wrapped around */
+		if (temp_start < start || temp_start < kbuf->buf_min ||
+		    temp_start > end)
 			return 0;
 
 		temp_end = temp_start + kbuf->memsz - 1;
@@ -503,6 +506,13 @@ static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
 			continue;
 		}
 
+		poison = range_first_hwpoison(temp_start, kbuf->memsz);
+		if (poison != PHYS_ADDR_MAX) {
+			/* we hit a poisoned page */
+			temp_start = poison - kbuf->memsz;
+			continue;
+		}
+
 		/* We found a suitable memory range */
 		break;
 	} while (1);
@@ -519,6 +529,7 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
 {
 	struct kimage *image = kbuf->image;
 	unsigned long temp_start, temp_end;
+	phys_addr_t poison;
 
 	temp_start = max(start, kbuf->buf_min);
 
@@ -545,6 +556,13 @@ static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
 			continue;
 		}
 
+		poison = range_last_hwpoison(temp_start, kbuf->memsz);
+		if (poison != PHYS_ADDR_MAX) {
+			/* we hit a poisoned page */
+			temp_start = poison + PAGE_SIZE;
+			continue;
+		}
+
 		/* We found a suitable memory range */
 		break;
 	} while (1);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index a8b03e2920ba8..a2ca8df501cae 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -96,6 +96,46 @@ void num_poisoned_pages_sub(unsigned long pfn, long i)
 		memblk_nr_poison_sub(pfn, i);
 }
 
+/*
+ * Return the first or the last hardware-poisoned online page in [start,
+ * start + size), or PHYS_ADDR_MAX if the range is clean.
+ */
+static phys_addr_t range_hwpoison(phys_addr_t start, unsigned long size,
+				  bool first)
+{
+	phys_addr_t poison = PHYS_ADDR_MAX;
+	unsigned long pfn, end_pfn;
+
+	if (!size || !atomic_long_read(&num_poisoned_pages))
+		return poison;
+
+	end_pfn = PHYS_PFN(start + size - 1);
+	for (pfn = PHYS_PFN(start); pfn <= end_pfn; pfn++) {
+		struct page *page = pfn_to_online_page(pfn);
+
+		if (page && is_page_hwpoison(page)) {
+			if (first)
+				return PFN_PHYS(pfn);
+
+			poison = PFN_PHYS(pfn);
+		}
+
+		cond_resched();
+	}
+
+	return poison;
+}
+
+phys_addr_t range_first_hwpoison(phys_addr_t start, unsigned long size)
+{
+	return range_hwpoison(start, size, true);
+}
+
+phys_addr_t range_last_hwpoison(phys_addr_t start, unsigned long size)
+{
+	return range_hwpoison(start, size, false);
+}
+
 /**
  * MF_ATTR_RO - Create sysfs entry for each memory failure statistics.
  * @_name: name of the file in the per NUMA sysfs directory.

gemini-3.1-pro-preview

null

null

							input: 3754
							output: 125
							thoughts: 1037
						

**KMSAN Assessment: No New Risks Here**

Okay, let's break this down. My initial assessment is that this patch series is focused on *preventing* the use of hardware-poisoned memory within the kexec process, not introducing new uninitialized memory vulnerabilities. We're modifying how kexec handles memory, specifically to *avoid* bad memory, which is a good thing.

The patch touches `mm.h`, `kexec_core.c`, `kexec_file.c`, and `memory-failure.c`. I need to confirm that these modifications don't introduce any new KMSAN-relevant issues, particularly related to uninitialized memory.

First, `sanity_check_segment_list` now validates kexec segments against poisoned memory. It uses `range_first_hwpoison` and returns an error if any poisoned memory is found. This is a *validation* step. I don't see any risk here; we're rejecting problematic segments, not using uninitialized data.

Next, `locate_mem_hole_top_down` and `locate_mem_hole_bottom_up` now include checks for poisoned memory using `range_first_hwpoison` or `range_last_hwpoison`. They're *allocating* memory for kexec segments, but now they are actively avoiding poisoned memory regions. The functions adjust their search based on the poisoned status of the candidate region. Crucially, they do not read from uninitialized memory. They are merely using a function to avoid potentially problematic regions.

Finally, `range_hwpoison` just iterates through a physical address range and calls `is_page_hwpoison`. Again, it's about detecting and reporting poisoned pages, not *creating* them or exposing them.

So, let's summarize the key points:

*   The patch *doesn't* introduce new kernel structures that get sent to userspace with uninitialized fields.
*   No conditional logic depends on potentially uninitialized variables; the code seems clean with proper initialization.
*   No complex data structures are allocated and left uninitialized.
*   The bounds checks have been updated to *avoid* using poisoned memory. This is exactly what we want. It doesn't allow accesses to uninitialized bytes of *existing* buffers.

Therefore, since the patch's primary function is to *avoid* the utilization of hardware-poisoned memory during kexec, it does not involve data transfer to userspace, nor does it create any potential of uninitialized memory. The code itself, that I've reviewed, appears to be properly initialized as well. I don't see a risk that justifies a dedicated KMSAN fuzzing session. KASAN and other standard bug detectors should be sufficient.

Okay, let me do one last spot check. In `locate_mem_hole_top_down` and `locate_mem_hole_bottom_up`, the variable `poison` is always assigned before it's used. Same with `range_hwpoison`; all variables in that function are also initialized. All clear there.

**Final conclusion: NeedsKMSAN = false.** The patch doesn't introduce any uninitialized memory risks. We're good.

{
  "KMSANReasoning": "The patch adds checks to avoid hardware-poisoned memory during kexec segment allocation and validation. It modifies memory allocation logic to skip poisoned pages and rejects kexec segments that land on poisoned memory. It does not introduce new data structures copied to user space, nor does it leave any variables or struct fields uninitialized. There is no risk of uninitialized memory usage or info-leaks, so a dedicated KMSAN session is not required. Standard KASAN and other bug detectors are sufficient.",
  "NeedsKMSAN": false
}

{
  "KMSANReasoning": "The patch adds checks to avoid hardware-poisoned memory during kexec segment allocation and validation. It modifies memory allocation logic to skip poisoned pages and rejects kexec segments that land on poisoned memory. It does not introduce new data structures copied to user space, nor does it leave any variables or struct fields uninitialized. There is no risk of uninitialized memory usage or info-leaks, so a dedicated KMSAN session is not required. Standard KASAN and other bug detectors are sufficient.",
  "NeedsKMSAN": false
}