AI Trajectory

null

{
  "EnableConfigs": [
    "INET"
  ],
  "FocusSymbols": [
    "proc_tcp_child_ehash_entries"
  ],
  "Reasoning": "The patch adds a capability check (CAP_NET_ADMIN) to the sysctl handler for tcp_child_ehash_entries. This is a functional change that alters the permissions required to modify this sysctl, and it should be fuzzed to ensure the check is correctly enforced without causing unintended side effects.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit cebe9e91a5294a5a689ee97de1abfe4d14facdde\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Sun Jun 28 11:49:32 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c\nindex ca1180dba1dea9..1cad1b5cb82682 100644\n--- a/net/ipv4/sysctl_net_ipv4.c\n+++ b/net/ipv4/sysctl_net_ipv4.c\n@@ -9,6 +9,7 @@\n #include \u003clinux/sysctl.h\u003e\n #include \u003clinux/seqlock.h\u003e\n #include \u003clinux/init.h\u003e\n+#include \u003clinux/capability.h\u003e\n #include \u003clinux/slab.h\u003e\n #include \u003cnet/icmp.h\u003e\n #include \u003cnet/ip.h\u003e\n@@ -415,6 +416,16 @@ static int proc_tcp_ehash_entries(const struct ctl_table *table, int write,\n \treturn proc_dointvec(\u0026tbl, write, buffer, lenp, ppos);\n }\n \n+static int proc_tcp_child_ehash_entries(const struct ctl_table *table, int write,\n+\t\t\t\t\tvoid *buffer, size_t *lenp,\n+\t\t\t\t\tloff_t *ppos)\n+{\n+\tif (write \u0026\u0026 !capable(CAP_NET_ADMIN))\n+\t\treturn -EPERM;\n+\n+\treturn proc_douintvec_minmax(table, write, buffer, lenp, ppos);\n+}\n+\n static int proc_udp_hash_entries(const struct ctl_table *table, int write,\n \t\t\t\t void *buffer, size_t *lenp, loff_t *ppos)\n {\n@@ -1524,7 +1535,7 @@ static struct ctl_table ipv4_net_table[] = {\n \t\t.data\t\t= \u0026init_net.ipv4.sysctl_tcp_child_ehash_entries,\n \t\t.maxlen\t\t= sizeof(unsigned int),\n \t\t.mode\t\t= 0644,\n-\t\t.proc_handler\t= proc_douintvec_minmax,\n+\t\t.proc_handler\t= proc_tcp_child_ehash_entries,\n \t\t.extra1\t\t= SYSCTL_ZERO,\n \t\t.extra2\t\t= \u0026tcp_child_ehash_entries_max,\n \t},\n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "INET"
  ],
  "FocusSymbols": [
    "proc_tcp_child_ehash_entries"
  ],
  "Reasoning": "The patch adds a capability check (CAP_NET_ADMIN) to the sysctl handler for tcp_child_ehash_entries. This is a functional change that alters the permissions required to modify this sysctl, and it should be fuzzed to ensure the check is correctly enforced without causing unintended side effects.",
  "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 cebe9e91a5294a5a689ee97de1abfe4d14facdde
Author: syz-cluster <triage@syzkaller.com>
Date:   Sun Jun 28 11:49:32 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index ca1180dba1dea9..1cad1b5cb82682 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -9,6 +9,7 @@
 #include <linux/sysctl.h>
 #include <linux/seqlock.h>
 #include <linux/init.h>
+#include <linux/capability.h>
 #include <linux/slab.h>
 #include <net/icmp.h>
 #include <net/ip.h>
@@ -415,6 +416,16 @@ static int proc_tcp_ehash_entries(const struct ctl_table *table, int write,
 	return proc_dointvec(&tbl, write, buffer, lenp, ppos);
 }
 
+static int proc_tcp_child_ehash_entries(const struct ctl_table *table, int write,
+					void *buffer, size_t *lenp,
+					loff_t *ppos)
+{
+	if (write && !capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	return proc_douintvec_minmax(table, write, buffer, lenp, ppos);
+}
+
 static int proc_udp_hash_entries(const struct ctl_table *table, int write,
 				 void *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -1524,7 +1535,7 @@ static struct ctl_table ipv4_net_table[] = {
 		.data		= &init_net.ipv4.sysctl_tcp_child_ehash_entries,
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
-		.proc_handler	= proc_douintvec_minmax,
+		.proc_handler	= proc_tcp_child_ehash_entries,
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= &tcp_child_ehash_entries_max,
 	},

gemini-3.1-pro-preview

null

null

							input: 2183
							output: 35
							thoughts: 223
						

**Analyzing a Network Security Patch**

Okay, so I'm looking at this patch that tweaks `net/ipv4/sysctl_net_ipv4.c`. It seems they're making a security-related change to the `tcp_child_ehash_entries` sysctl. Instead of the usual `proc_douintvec_minmax` handler, they're now using a new function, `proc_tcp_child_ehash_entries`. My initial thought is that this likely introduces a capability check, specifically for `CAP_NET_ADMIN`, before allowing writes to this sysctl.

The core of the change seems straightforward: verify `CAP_NET_ADMIN`. If the user has it, proceed with the original `proc_douintvec_minmax`; otherwise, return `-EPERM`, indicating a permission error. This is a functional change, aimed at tightening security by restricting who can modify this particular network setting.

Naturally, my mind immediately jumps to fuzzing. I need to make sure this capability check actually works as designed and doesn’t introduce any unexpected side effects or regressions. A thorough fuzzing campaign is essential to validate the intended behavior and identify any potential vulnerabilities.

Now, let's get into the specifics. I need to pinpoint the relevant config options and focus on the important symbols. I'll need to figure out the exact configuration options. The file is, as mentioned, `net/ipv4/sysctl_net_ipv4.c`. I'll want to check `net/ipv4/Makefile` to locate the relevant config options, is it `CONFIG_INET`, `CONFIG_IP_TCP`, or something similar? Gotta be precise here.

{
  "Expression": "sysctl_net_ipv4.o",
  "PathPrefix": "net/ipv4/Makefile"
}

{
  "Output": "net/ipv4/Makefile=19=obj-$(CONFIG_NET_IP_TUNNEL) += ip_tunnel.o\nnet/ipv4/Makefile:20:obj-$(CONFIG_SYSCTL) += sysctl_net_ipv4.o\nnet/ipv4/Makefile-21-obj-$(CONFIG_PROC_FS) += proc.o\n"
}

gemini-3.1-pro-preview

null

null

							input: 2892
							output: 42
							thoughts: 39
						

Okay, here's my interpretation of that thought process, as if I were thinking it myself, with a focus tailored for an expert audience:

**Investigating a Potentially Missing Kernel Configuration**

Alright, so `CONFIG_SYSCTL` is required here. That's usually baked in; it's practically a given. But I need to be absolutely sure. My main concern right now is that I see a specific value that I'm not familiar with, `tcp_child_ehash_entries` and I need to figure out its dependencies. Let me dig into the kernel config system and see if this particular option, `tcp_child_ehash_entries`, is tucked behind some obscure or niche configuration flag. It's likely a modular setting, but I've got to confirm if it has any odd dependencies or preconditions. A quick grep of the Kconfig files should provide the answer, and then I can verify it in the live kernel. I'm looking for anything unusual here. If `CONFIG_SYSCTL` is on, the problem must be elsewhere.

{
  "Expression": "tcp_child_ehash_entries",
  "PathPrefix": "net/ipv4/sysctl_net_ipv4.c"
}

{
  "Output": "net/ipv4/sysctl_net_ipv4.c=44=static u32 fib_multipath_hash_fields_all_mask __maybe_unused =\nnet/ipv4/sysctl_net_ipv4.c-45-\tFIB_MULTIPATH_HASH_FIELD_ALL_MASK;\nnet/ipv4/sysctl_net_ipv4.c:46:static unsigned int tcp_child_ehash_entries_max = 16 * 1024 * 1024;\nnet/ipv4/sysctl_net_ipv4.c-47-static unsigned int udp_child_hash_entries_max = UDP_HTABLE_SIZE_MAX;\n--\nnet/ipv4/sysctl_net_ipv4.c=395=static int proc_tcp_ehash_entries(const struct ctl_table *table, int write,\n--\nnet/ipv4/sysctl_net_ipv4.c-398-\tstruct net *net = container_of(table-\u003edata, struct net,\nnet/ipv4/sysctl_net_ipv4.c:399:\t\t\t\t       ipv4.sysctl_tcp_child_ehash_entries);\nnet/ipv4/sysctl_net_ipv4.c-400-\tstruct inet_hashinfo *hinfo = net-\u003eipv4.tcp_death_row.hashinfo;\n--\nnet/ipv4/sysctl_net_ipv4.c-418-\nnet/ipv4/sysctl_net_ipv4.c:419:static int proc_tcp_child_ehash_entries(const struct ctl_table *table, int write,\nnet/ipv4/sysctl_net_ipv4.c-420-\t\t\t\t\tvoid *buffer, size_t *lenp,\n--\nnet/ipv4/sysctl_net_ipv4.c=638=static struct ctl_table ipv4_net_table[] = {\n--\nnet/ipv4/sysctl_net_ipv4.c-1528-\t\t.procname\t= \"tcp_ehash_entries\",\nnet/ipv4/sysctl_net_ipv4.c:1529:\t\t.data\t\t= \u0026init_net.ipv4.sysctl_tcp_child_ehash_entries,\nnet/ipv4/sysctl_net_ipv4.c-1530-\t\t.mode\t\t= 0444,\n--\nnet/ipv4/sysctl_net_ipv4.c-1533-\t{\nnet/ipv4/sysctl_net_ipv4.c:1534:\t\t.procname\t= \"tcp_child_ehash_entries\",\nnet/ipv4/sysctl_net_ipv4.c:1535:\t\t.data\t\t= \u0026init_net.ipv4.sysctl_tcp_child_ehash_entries,\nnet/ipv4/sysctl_net_ipv4.c-1536-\t\t.maxlen\t\t= sizeof(unsigned int),\nnet/ipv4/sysctl_net_ipv4.c-1537-\t\t.mode\t\t= 0644,\nnet/ipv4/sysctl_net_ipv4.c:1538:\t\t.proc_handler\t= proc_tcp_child_ehash_entries,\nnet/ipv4/sysctl_net_ipv4.c-1539-\t\t.extra1\t\t= SYSCTL_ZERO,\nnet/ipv4/sysctl_net_ipv4.c:1540:\t\t.extra2\t\t= \u0026tcp_child_ehash_entries_max,\nnet/ipv4/sysctl_net_ipv4.c-1541-\t},\n"
}

gemini-3.1-pro-preview

null

null

							input: 4093
							output: 40
							thoughts: 23
						

Okay, here's my interpretation of those thoughts, crafted with the understanding that I'm discussing this with a fellow expert:

**Investigating the IPv4 Network Table Configuration**

Alright, so the `sysctl` setting I'm looking for seems to be hanging out in the `ipv4_net_table`. Right, good start. Now, the key question is, are there any *specific* configurations or parameters associated with this particular table that I should be aware of? I need to dig deeper here. It's not enough to know *where* the setting is; I need to understand *how* it's configured and what levers I can pull. Any relevant config options, kernel tuning parameters, or implications for routing or network performance are now my focus. Time to dive into the details.

{
  "Expression": "ipv4_net_table",
  "PathPrefix": "net/ipv4/sysctl_net_ipv4.c"
}

{
  "Output": "net/ipv4/sysctl_net_ipv4.c=541=static struct ctl_table ipv4_table[] = {\n--\nnet/ipv4/sysctl_net_ipv4.c-637-\nnet/ipv4/sysctl_net_ipv4.c:638:static struct ctl_table ipv4_net_table[] = {\nnet/ipv4/sysctl_net_ipv4.c-639-\t{\n--\nnet/ipv4/sysctl_net_ipv4.c=1668=static __net_init int ipv4_sysctl_init_net(struct net *net)\nnet/ipv4/sysctl_net_ipv4.c-1669-{\nnet/ipv4/sysctl_net_ipv4.c:1670:\tsize_t table_size = ARRAY_SIZE(ipv4_net_table);\nnet/ipv4/sysctl_net_ipv4.c-1671-\tstruct ctl_table *table;\nnet/ipv4/sysctl_net_ipv4.c-1672-\nnet/ipv4/sysctl_net_ipv4.c:1673:\ttable = ipv4_net_table;\nnet/ipv4/sysctl_net_ipv4.c-1674-\tif (!net_eq(net, \u0026init_net)) {\n--\nnet/ipv4/sysctl_net_ipv4.c-1676-\nnet/ipv4/sysctl_net_ipv4.c:1677:\t\ttable = kmemdup(table, sizeof(ipv4_net_table), GFP_KERNEL);\nnet/ipv4/sysctl_net_ipv4.c-1678-\t\tif (!table)\n"
}

gemini-3.1-pro-preview

null

null

							input: 4763
							output: 110
							thoughts: 91
						

**My Assessment of the Recent IPv4 Sysctl Change**

Okay, so I'm looking at this change, and honestly, it's pretty straightforward. We're dealing with standard IPv4 sysctls here; nothing particularly exotic or groundbreaking from the overall scope. The core addition is this `proc_tcp_child_ehash_entries` function – that's the one I need to focus on.

Functionally, it seems to be just a matter of adding a capability check, which is good security practice. But, anytime there's a modification like this, especially touching something that could potentially affect network behavior, it warrants a closer look.

My immediate thought is that this would be a high-yield target for fuzzing. The change is specific enough that I can zero in on the key symbol: `proc_tcp_child_ehash_entries`.

Config-wise, we’re looking at `INET`, and `SYSCTL`, but `SYSCTL` is almost always enabled. `INET` is really the main relevant dependency. I'll make a note of this. I'll need to remember to focus any tests on systems configured to support IPv4.

{
  "EnableConfigs": [
    "INET"
  ],
  "FocusSymbols": [
    "proc_tcp_child_ehash_entries"
  ],
  "Reasoning": "The patch adds a capability check (CAP_NET_ADMIN) to the sysctl handler for tcp_child_ehash_entries. This is a functional change that alters the permissions required to modify this sysctl, and it should be fuzzed to ensure the check is correctly enforced without causing unintended side effects.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "INET"
  ],
  "FocusSymbols": [
    "proc_tcp_child_ehash_entries"
  ],
  "Reasoning": "The patch adds a capability check (CAP_NET_ADMIN) to the sysctl handler for tcp_child_ehash_entries. This is a functional change that alters the permissions required to modify this sysctl, and it should be fuzzed to ensure the check is correctly enforced without causing unintended side effects.",
  "WorthFuzzing": true
}