AI Trajectory

null

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "__htab_map_lookup_and_delete_batch",
    "htab_map_lookup_batch",
    "htab_map_lookup_and_delete_batch",
    "htab_percpu_map_lookup_batch",
    "htab_percpu_map_lookup_and_delete_batch",
    "htab_lru_map_lookup_batch",
    "htab_lru_map_lookup_and_delete_batch",
    "htab_lru_percpu_map_lookup_batch",
    "htab_lru_percpu_map_lookup_and_delete_batch"
  ],
  "Reasoning": "The patch modifies the BPF hash table map batch lookup and delete logic to periodically yield the CPU when scanning a large number of empty buckets. This is a functional change in the core BPF map implementation that prevents soft lockups and should be fuzzed to ensure correctness and absence of regressions (e.g., race conditions or incorrect batch iteration).",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 43f32635cf1c1b2815e07a9f88069d6f9957a052\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Fri Jul 10 21:03:01 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c\nindex 9f394e1aa2e85b..b208a567892ae8 100644\n--- a/kernel/bpf/hashtab.c\n+++ b/kernel/bpf/hashtab.c\n@@ -1769,6 +1769,11 @@ static int htab_lru_percpu_map_lookup_and_delete_elem(struct bpf_map *map,\n \t\t\t\t\t\t flags);\n }\n \n+/* Max consecutive empty buckets to walk in one RCU +\n+ * instrumentation-disabled section before rescheduling.\n+ */\n+#define HTAB_BATCH_EMPTY_RESCHED 64\n+\n static int\n __htab_map_lookup_and_delete_batch(struct bpf_map *map,\n \t\t\t\t   const union bpf_attr *attr,\n@@ -1790,6 +1795,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,\n \tunsigned long flags = 0;\n \tbool locked = false;\n \tstruct htab_elem *l;\n+\tu32 empty_cnt = 0;\n \tstruct bucket *b;\n \tint ret = 0;\n \n@@ -1969,11 +1975,19 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,\n \n next_batch:\n \t/* If we are not copying data, we can go to next bucket and avoid\n-\t * unlocking the rcu.\n+\t * unlocking the rcu. Bound the walk though: after\n+\t * HTAB_BATCH_EMPTY_RESCHED consecutive empty buckets, fully exit\n+\t * the critical section (no locks are held here) and reschedule.\n \t */\n \tif (!bucket_cnt \u0026\u0026 (batch + 1 \u003c htab-\u003en_buckets)) {\n \t\tbatch++;\n-\t\tgoto again_nocopy;\n+\t\tif (++empty_cnt \u003c HTAB_BATCH_EMPTY_RESCHED)\n+\t\t\tgoto again_nocopy;\n+\t\tempty_cnt = 0;\n+\t\trcu_read_unlock();\n+\t\tbpf_enable_instrumentation();\n+\t\tcond_resched();\n+\t\tgoto again;\n \t}\n \n \trcu_read_unlock();\n@@ -1987,11 +2001,13 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,\n \t}\n \n \ttotal += bucket_cnt;\n+\tempty_cnt = 0;\n \tbatch++;\n \tif (batch \u003e= htab-\u003en_buckets) {\n \t\tret = -ENOENT;\n \t\tgoto after_loop;\n \t}\n+\tcond_resched();\n \tgoto again;\n \n after_loop:\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "__htab_map_lookup_and_delete_batch",
    "htab_map_lookup_batch",
    "htab_map_lookup_and_delete_batch",
    "htab_percpu_map_lookup_batch",
    "htab_percpu_map_lookup_and_delete_batch",
    "htab_lru_map_lookup_batch",
    "htab_lru_map_lookup_and_delete_batch",
    "htab_lru_percpu_map_lookup_batch",
    "htab_lru_percpu_map_lookup_and_delete_batch"
  ],
  "Reasoning": "The patch modifies the BPF hash table map batch lookup and delete logic to periodically yield the CPU when scanning a large number of empty buckets. This is a functional change in the core BPF map implementation that prevents soft lockups and should be fuzzed to ensure correctness and absence of regressions (e.g., race conditions or incorrect batch iteration).",
  "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 43f32635cf1c1b2815e07a9f88069d6f9957a052
Author: syz-cluster <triage@syzkaller.com>
Date:   Fri Jul 10 21:03:01 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 9f394e1aa2e85b..b208a567892ae8 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1769,6 +1769,11 @@ static int htab_lru_percpu_map_lookup_and_delete_elem(struct bpf_map *map,
 						 flags);
 }
 
+/* Max consecutive empty buckets to walk in one RCU +
+ * instrumentation-disabled section before rescheduling.
+ */
+#define HTAB_BATCH_EMPTY_RESCHED 64
+
 static int
 __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 				   const union bpf_attr *attr,
@@ -1790,6 +1795,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 	unsigned long flags = 0;
 	bool locked = false;
 	struct htab_elem *l;
+	u32 empty_cnt = 0;
 	struct bucket *b;
 	int ret = 0;
 
@@ -1969,11 +1975,19 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 
 next_batch:
 	/* If we are not copying data, we can go to next bucket and avoid
-	 * unlocking the rcu.
+	 * unlocking the rcu. Bound the walk though: after
+	 * HTAB_BATCH_EMPTY_RESCHED consecutive empty buckets, fully exit
+	 * the critical section (no locks are held here) and reschedule.
 	 */
 	if (!bucket_cnt && (batch + 1 < htab->n_buckets)) {
 		batch++;
-		goto again_nocopy;
+		if (++empty_cnt < HTAB_BATCH_EMPTY_RESCHED)
+			goto again_nocopy;
+		empty_cnt = 0;
+		rcu_read_unlock();
+		bpf_enable_instrumentation();
+		cond_resched();
+		goto again;
 	}
 
 	rcu_read_unlock();
@@ -1987,11 +2001,13 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
 	}
 
 	total += bucket_cnt;
+	empty_cnt = 0;
 	batch++;
 	if (batch >= htab->n_buckets) {
 		ret = -ENOENT;
 		goto after_loop;
 	}
+	cond_resched();
 	goto again;
 
 after_loop:

gemini-3.1-pro-preview

null

null

							input: 2343
							output: 27
							thoughts: 182
						

**Analyzing a BPF Hash Table Modification**

Okay, so I've got a patch here that's tweaking the `kernel/bpf/hashtab.c` file. Specifically, it's messing with `__htab_map_lookup_and_delete_batch`. Interesting. It sounds like they're adding a limit to the number of consecutive empty buckets we walk through in a single RCU section when instrumentation is disabled within that function. This is definitely a functional change in the BPF hash table implementation itself. My first thought is to understand the implications of this change.

Now, let me think about any potential configuration dependencies. BPF is usually enabled, but `CONFIG_BPF_SYSCALL` is a key one to keep in mind. We might need to consider how this interacts with different BPF deployment scenarios.

My next step is to dive right into the code. I'll need to focus on `kernel/bpf/hashtab.c` and that `__htab_map_lookup_and_delete_batch` function. I think a good starting point is to grep the codebase for that function name to get a picture of how it's used and where this change is most relevant.

{
  "Expression": "__htab_map_lookup_and_delete_batch"
}

{
  "Output": "kernel/bpf/hashtab.c=1777=static int\nkernel/bpf/hashtab.c:1778:__htab_map_lookup_and_delete_batch(struct bpf_map *map,\nkernel/bpf/hashtab.c-1779-\t\t\t\t   const union bpf_attr *attr,\n--\nkernel/bpf/hashtab.c=2030=htab_percpu_map_lookup_batch(struct bpf_map *map, const union bpf_attr *attr,\n--\nkernel/bpf/hashtab.c-2032-{\nkernel/bpf/hashtab.c:2033:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, false,\nkernel/bpf/hashtab.c-2034-\t\t\t\t\t\t  false, true);\n--\nkernel/bpf/hashtab.c=2038=htab_percpu_map_lookup_and_delete_batch(struct bpf_map *map,\n--\nkernel/bpf/hashtab.c-2041-{\nkernel/bpf/hashtab.c:2042:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, true,\nkernel/bpf/hashtab.c-2043-\t\t\t\t\t\t  false, true);\n--\nkernel/bpf/hashtab.c=2047=htab_map_lookup_batch(struct bpf_map *map, const union bpf_attr *attr,\n--\nkernel/bpf/hashtab.c-2049-{\nkernel/bpf/hashtab.c:2050:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, false,\nkernel/bpf/hashtab.c-2051-\t\t\t\t\t\t  false, false);\n--\nkernel/bpf/hashtab.c=2055=htab_map_lookup_and_delete_batch(struct bpf_map *map,\n--\nkernel/bpf/hashtab.c-2058-{\nkernel/bpf/hashtab.c:2059:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, true,\nkernel/bpf/hashtab.c-2060-\t\t\t\t\t\t  false, false);\n--\nkernel/bpf/hashtab.c=2064=htab_lru_percpu_map_lookup_batch(struct bpf_map *map,\n--\nkernel/bpf/hashtab.c-2067-{\nkernel/bpf/hashtab.c:2068:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, false,\nkernel/bpf/hashtab.c-2069-\t\t\t\t\t\t  true, true);\n--\nkernel/bpf/hashtab.c=2073=htab_lru_percpu_map_lookup_and_delete_batch(struct bpf_map *map,\n--\nkernel/bpf/hashtab.c-2076-{\nkernel/bpf/hashtab.c:2077:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, true,\nkernel/bpf/hashtab.c-2078-\t\t\t\t\t\t  true, true);\n--\nkernel/bpf/hashtab.c=2082=htab_lru_map_lookup_batch(struct bpf_map *map, const union bpf_attr *attr,\n--\nkernel/bpf/hashtab.c-2084-{\nkernel/bpf/hashtab.c:2085:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, false,\nkernel/bpf/hashtab.c-2086-\t\t\t\t\t\t  true, false);\n--\nkernel/bpf/hashtab.c=2090=htab_lru_map_lookup_and_delete_batch(struct bpf_map *map,\n--\nkernel/bpf/hashtab.c-2093-{\nkernel/bpf/hashtab.c:2094:\treturn __htab_map_lookup_and_delete_batch(map, attr, uattr, true,\nkernel/bpf/hashtab.c-2095-\t\t\t\t\t\t  true, false);\n"
}

gemini-3.1-pro-preview

null

null

							input: 3900
							output: 21
							thoughts: 197
						

**Analyzing the Core Batch Lookup and Delete Function**

Okay, so I'm looking at `__htab_map_lookup_and_delete_batch`. The call graph is interesting. I'm seeing this function get invoked by a whole slew of batch map operations – it's the core, it seems. We've got `htab_percpu_map_lookup_batch`, `htab_percpu_map_lookup_and_delete_batch`, then the non-percpu versions like `htab_map_lookup_batch` and `htab_map_lookup_and_delete_batch`. There are the LRU variants in there as well. Essentially, this is the backbone for a lot of BPF map batch processing.

Right, so this function’s a fundamental building block.  Naturally, `CONFIG_BPF_SYSCALL` is a requirement, but I need to make sure I'm not missing any other dependencies here. Given the centrality of this function to a variety of map operations, there could be other configuration options that are necessary to fully support its behavior, particularly around concurrency or resource management. I’ll need to delve deeper into the surrounding code and possibly the documentation to ensure nothing is overlooked.

{
  "Expression": "config BPF_SYSCALL"
}

{
  "Output": "kernel/bpf/Kconfig=25=menu \"BPF subsystem\"\nkernel/bpf/Kconfig-26-\nkernel/bpf/Kconfig:27:config BPF_SYSCALL\nkernel/bpf/Kconfig-28-\tbool \"Enable bpf() system call\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 4464
							output: 252
							thoughts: 404
						

**Analyzing the BPF Map Batch Lookup/Delete Patch**

Okay, so this patch is aimed at preventing soft lockups within the BPF map batch lookup and delete functions, specifically when dealing with a lot of empty buckets. This is a functional change, a core modification to how BPF maps work, so it *absolutely* needs fuzzing. The goal is to verify the change's correctness and make sure it doesn't introduce any new regressions. I'm thinking, potential race conditions or even incorrect iteration in the batch operations are prime candidates for failure.

My focus should be on these key symbols:

*   `__htab_map_lookup_and_delete_batch`
*   `htab_map_lookup_batch`
*   `htab_map_lookup_and_delete_batch`
*   `htab_percpu_map_lookup_batch`
*   `htab_percpu_map_lookup_and_delete_batch`
*   `htab_lru_map_lookup_batch`
*   `htab_lru_map_lookup_and_delete_batch`
*   `htab_lru_percpu_map_lookup_batch`
*   `htab_lru_percpu_map_lookup_and_delete_batch`

Let's quickly confirm if `__htab_map_lookup_and_delete_batch` is static. Yes, it is. I'm also going to note that the exported/map operations functions are `htab_map_lookup_batch`, `htab_map_lookup_and_delete_batch`, etc.

I'll use `BPF_SYSCALL` as the enable config for fuzzing.

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "__htab_map_lookup_and_delete_batch",
    "htab_map_lookup_batch",
    "htab_map_lookup_and_delete_batch",
    "htab_percpu_map_lookup_batch",
    "htab_percpu_map_lookup_and_delete_batch",
    "htab_lru_map_lookup_batch",
    "htab_lru_map_lookup_and_delete_batch",
    "htab_lru_percpu_map_lookup_batch",
    "htab_lru_percpu_map_lookup_and_delete_batch"
  ],
  "Reasoning": "The patch modifies the BPF hash table map batch lookup and delete logic to periodically yield the CPU when scanning a large number of empty buckets. This is a functional change in the core BPF map implementation that prevents soft lockups and should be fuzzed to ensure correctness and absence of regressions (e.g., race conditions or incorrect batch iteration).",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "__htab_map_lookup_and_delete_batch",
    "htab_map_lookup_batch",
    "htab_map_lookup_and_delete_batch",
    "htab_percpu_map_lookup_batch",
    "htab_percpu_map_lookup_and_delete_batch",
    "htab_lru_map_lookup_batch",
    "htab_lru_map_lookup_and_delete_batch",
    "htab_lru_percpu_map_lookup_batch",
    "htab_lru_percpu_map_lookup_and_delete_batch"
  ],
  "Reasoning": "The patch modifies the BPF hash table map batch lookup and delete logic to periodically yield the CPU when scanning a large number of empty buckets. This is a functional change in the core BPF map implementation that prevents soft lockups and should be fuzzed to ensure correctness and absence of regressions (e.g., race conditions or incorrect batch iteration).",
  "WorthFuzzing": true
}