[syzbot] [wireless?] WARNING in drv_get_tsf (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 944aacb68baf Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15f88dfa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16259d9a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1971a9dd2936/disk-944aacb6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cf50ec150c97/vmlinux-944aacb6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/eee3d7722c03/bzImage-944aacb6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2cecf0...@syzkaller.appspotmail.com

------------[ cut here ]------------
wlan1: Failed check-sdata-in-driver check, flags: 0x0
WARNING: net/mac80211/driver-ops.c:255 at drv_get_tsf+0x187/0x6f0 net/mac80211/driver-ops.c:255, CPU#0: kworker/u8:11/3538
Modules linked in:
CPU: 0 UID: 0 PID: 3538 Comm: kworker/u8:11 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound cfg80211_wiphy_work
RIP: 0010:drv_get_tsf+0x18d/0x6f0 net/mac80211/driver-ops.c:255
Code: 0a 00 00 4d 85 e4 0f 84 95 04 00 00 e8 8c 9a dc f6 49 81 c4 20 01 00 00 e8 80 9a dc f6 48 8d 3d 49 e9 b6 05 44 89 f2 4c 89 e6 <67> 48 0f b9 3a e8 69 9a dc f6 4c 89 ea 48 b8 00 00 00 00 00 fc ff
RSP: 0018:ffffc9000c49fb08 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88805c0c4d80 RCX: ffffffff8ae1c32f
RDX: 0000000000000000 RSI: ffff88805c0c4120 RDI: ffffffff9098acd0
RBP: ffff888031cc8e80 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: ffff88803190c830 R12: ffff88805c0c4120
R13: ffff88805c0c57b8 R14: 0000000000000000 R15: ffff888031cc86d0
FS: 0000000000000000(0000) GS:ffff8881248f9000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f239b3156c0 CR3: 0000000075ed0000 CR4: 00000000003526f0
Call Trace:
<TASK>
ieee80211_if_fmt_tsf+0x42/0x70 net/mac80211/debugfs_netdev.c:659
wiphy_locked_debugfs_read_work+0xe6/0x1c0 net/wireless/debugfs.c:168
cfg80211_wiphy_work+0x3fb/0x560 net/wireless/core.c:438
process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
process_scheduled_works kernel/workqueue.c:3340 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>
----------------
Code disassembly (best guess), 1 bytes skipped:
0: 00 00 add %al,(%rax)
2: 4d 85 e4 test %r12,%r12
5: 0f 84 95 04 00 00 je 0x4a0
b: e8 8c 9a dc f6 call 0xf6dc9a9c
10: 49 81 c4 20 01 00 00 add $0x120,%r12
17: e8 80 9a dc f6 call 0xf6dc9a9c
1c: 48 8d 3d 49 e9 b6 05 lea 0x5b6e949(%rip),%rdi # 0x5b6e96c
23: 44 89 f2 mov %r14d,%edx
26: 4c 89 e6 mov %r12,%rsi
* 29: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2e: e8 69 9a dc f6 call 0xf6dc9a9c
33: 4c 89 ea mov %r13,%rdx
36: 48 rex.W
37: b8 00 00 00 00 mov $0x0,%eax
3c: 00 fc add %bh,%ah
3e: ff .byte 0xff


---
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If the report is already addressed, let syzbot know by replying with:
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[syzbot]

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***

Subject: Private message regarding: [syzbot] [wireless?] WARNING in drv_get_tsf (2)
Author: kapoor...@gmail.com

#syz test

commit 0cd0a5cff75a12d3cf1fa0675950ef0dcc647799 (HEAD -> master)
Author: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon Jan 19 03:03:18 2026 +0530

mac80211: Fix WARNING in drv_get_tsf debugfs access

The debugfs tsf read function was calling drv_get_tsf() even when the
interface was not registered with the driver, causing a WARN_ON to be
triggered. This is inappropriate for debugfs access.

Fix this by checking the IEEE80211_SDATA_IN_DRIVER flag in the debugfs
read function and returning -1ULL directly when the interface is not
in the driver, avoiding the warning.

Reported-by: syzbot+15f...@syzkaller.appspotmail.com
Signed-off-by: Arnav Kapoor <kapoor...@gmail.com>

diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index 30a5a978a..669e7c519 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -656,7 +656,10 @@ static ssize_t ieee80211_if_fmt_tsf(
struct ieee80211_local *local = sdata->local;
u64 tsf;

- tsf = drv_get_tsf(local, (struct ieee80211_sub_if_data *)sdata);
+ if (!(sdata->flags & IEEE80211_SDATA_IN_DRIVER))
+ tsf = -1ULL;
+ else
+ tsf = drv_get_tsf(local, (struct ieee80211_sub_if_data
*)sdata);

return scnprintf(buf, buflen, "0x%016llx\n", (unsigned long long)
tsf);

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=14da53fa580000

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Private message regarding: [syzbot] [wireless?] WARNING in drv_get_tsf (2)
Author: kapoor...@gmail.com

#syz test

From 0cd0a5cff75a12d3cf1fa0675950ef0dcc647799 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon, 19 Jan 2026 03:03:18 +0530
Subject: [PATCH] mac80211: Fix WARNING in drv_get_tsf debugfs access

The debugfs tsf read function was calling drv_get_tsf() even when the
interface was not registered with the driver, causing a WARN_ON to be
triggered. This is inappropriate for debugfs access.

Fix this by checking the IEEE80211_SDATA_IN_DRIVER flag in the debugfs
read function and returning -1ULL directly when the interface is not
in the driver, avoiding the warning.

Reported-by: syzbot+15f...@syzkaller.appspotmail.com

Signed-off-by: Arnav Rawat <arnavra...@gmail.com>
---
net/mac80211/debugfs_netdev.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c
index 30a5a978a..669e7c519 100644
--- a/net/mac80211/debugfs_netdev.c
+++ b/net/mac80211/debugfs_netdev.c
@@ -656,7 +656,10 @@ static ssize_t ieee80211_if_fmt_tsf(
struct ieee80211_local *local = sdata->local;
u64 tsf;

- tsf = drv_get_tsf(local, (struct ieee80211_sub_if_data *)sdata);
+ if (!(sdata->flags & IEEE80211_SDATA_IN_DRIVER))
+ tsf = -1ULL;
+ else
+ tsf = drv_get_tsf(local, (struct ieee80211_sub_if_data
*)sdata);

return scnprintf(buf, buflen, "0x%016llx\n", (unsigned long long)
tsf);
}

--
2.43.0

On Monday, 19 January 2026 at 03:18:05 UTC+5:30 syzbot wrote:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}'
token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function
returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=14da53fa580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=127ba852580000

[syzbot]

On Monday, 19 January 2026 at 03:39:05 UTC+5:30 syzbot wrote:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}'
token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function
returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=127ba852580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13ff6b9a580000

[syzbot]

On Monday, 19 January 2026 at 04:05:04 UTC+5:30 syzbot wrote:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}'
token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function
returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13ff6b9a580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13d7a852580000

[syzbot]

On Monday, 19 January 2026 at 04:18:05 UTC+5:30 syzbot wrote:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}'
token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function
returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=13d7a852580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1217db9a580000

[syzbot]

On Monday, 19 January 2026 at 04:32:04 UTC+5:30 syzbot wrote:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}'
token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function
returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1217db9a580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=100fdb9a580000

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Private message regarding: [syzbot] [wireless?] WARNING in drv_get_tsf (2)
Author: kapoor...@gmail.com

#syz test

From e0dd0088f4b871d8c44d5b9ba17dd9eba1f770a0 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon, 19 Jan 2026 04:48:19 +0530
Subject: [PATCH] netfilter: nf_conntrack: add entry limit and cond_resched
in
gc_worker

Further limit the gc_worker to process at most 100 entries per bucket
and add cond_resched() at the start of each entry processing to ensure
frequent yielding and prevent RCU stalls.

Reported-by: syzbot+8bb3e2...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8bb3e2bee8a429cc76dd
---
net/netfilter/nf_conntrack_core.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nf_conntrack_core.c
b/net/netfilter/nf_conntrack_core.c
index 8a2cdd172..ff901a2b4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1552,13 +1552,17 @@ static void gc_worker(struct work_struct *work)
break;
}

+ int entry_count = 0;
hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
struct nf_conntrack_net *cnet;
struct net *net;
long expires;

tmp = nf_ct_tuplehash_to_ctrack(h);
+ entry_count++;

+ if (entry_count > 100) break;
+ cond_resched();
if (expired_count > GC_SCAN_EXPIRED_MAX) {
rcu_read_unlock();

--
2.43.0From e0dd0088f4b871d8c44d5b9ba17dd9eba1f770a0 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon, 19 Jan 2026 04:48:19 +0530
Subject: [PATCH] netfilter: nf_conntrack: add entry limit and cond_resched
in
gc_worker

Further limit the gc_worker to process at most 100 entries per bucket
and add cond_resched() at the start of each entry processing to ensure
frequent yielding and prevent RCU stalls.

Reported-by: syzbot+8bb3e2...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8bb3e2bee8a429cc76dd
---
net/netfilter/nf_conntrack_core.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nf_conntrack_core.c
b/net/netfilter/nf_conntrack_core.c
index 8a2cdd172..ff901a2b4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1552,13 +1552,17 @@ static void gc_worker(struct work_struct *work)
break;
}

+ int entry_count = 0;
hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
struct nf_conntrack_net *cnet;
struct net *net;
long expires;

tmp = nf_ct_tuplehash_to_ctrack(h);
+ entry_count++;

+ if (entry_count > 100) break;
+ cond_resched();
if (expired_count > GC_SCAN_EXPIRED_MAX) {
rcu_read_unlock();

--
2.43.0From e0dd0088f4b871d8c44d5b9ba17dd9eba1f770a0 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon, 19 Jan 2026 04:48:19 +0530
Subject: [PATCH] netfilter: nf_conntrack: add entry limit and cond_resched
in
gc_worker

Further limit the gc_worker to process at most 100 entries per bucket
and add cond_resched() at the start of each entry processing to ensure
frequent yielding and prevent RCU stalls.

Reported-by: syzbot+8bb3e2...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8bb3e2bee8a429cc76dd
---
net/netfilter/nf_conntrack_core.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nf_conntrack_core.c
b/net/netfilter/nf_conntrack_core.c
index 8a2cdd172..ff901a2b4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1552,13 +1552,17 @@ static void gc_worker(struct work_struct *work)
break;
}

+ int entry_count = 0;
hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
struct nf_conntrack_net *cnet;
struct net *net;
long expires;

tmp = nf_ct_tuplehash_to_ctrack(h);
+ entry_count++;

+ if (entry_count > 100) break;
+ cond_resched();
if (expired_count > GC_SCAN_EXPIRED_MAX) {
rcu_read_unlock();

--
2.43.0From e0dd0088f4b871d8c44d5b9ba17dd9eba1f770a0 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon, 19 Jan 2026 04:48:19 +0530
Subject: [PATCH] netfilter: nf_conntrack: add entry limit and cond_resched
in
gc_worker

Further limit the gc_worker to process at most 100 entries per bucket
and add cond_resched() at the start of each entry processing to ensure
frequent yielding and prevent RCU stalls.

Reported-by: syzbot+8bb3e2...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8bb3e2bee8a429cc76dd
---
net/netfilter/nf_conntrack_core.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nf_conntrack_core.c
b/net/netfilter/nf_conntrack_core.c
index 8a2cdd172..ff901a2b4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1552,13 +1552,17 @@ static void gc_worker(struct work_struct *work)
break;
}

+ int entry_count = 0;
hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
struct nf_conntrack_net *cnet;
struct net *net;
long expires;

tmp = nf_ct_tuplehash_to_ctrack(h);
+ entry_count++;

+ if (entry_count > 100) break;
+ cond_resched();
if (expired_count > GC_SCAN_EXPIRED_MAX) {
rcu_read_unlock();

--
2.43.0From e0dd0088f4b871d8c44d5b9ba17dd9eba1f770a0 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>
Date: Mon, 19 Jan 2026 04:48:19 +0530
Subject: [PATCH] netfilter: nf_conntrack: add entry limit and cond_resched
in
gc_worker

Further limit the gc_worker to process at most 100 entries per bucket
and add cond_resched() at the start of each entry processing to ensure
frequent yielding and prevent RCU stalls.

Reported-by: syzbot+8bb3e2...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8bb3e2bee8a429cc76dd
---
net/netfilter/nf_conntrack_core.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nf_conntrack_core.c
b/net/netfilter/nf_conntrack_core.c
index 8a2cdd172..ff901a2b4 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1552,13 +1552,17 @@ static void gc_worker(struct work_struct *work)
break;
}

+ int entry_count = 0;
hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
struct nf_conntrack_net *cnet;
struct net *net;
long expires;

tmp = nf_ct_tuplehash_to_ctrack(h);
+ entry_count++;

+ if (entry_count > 100) break;
+ cond_resched();
if (expired_count > GC_SCAN_EXPIRED_MAX) {
rcu_read_unlock();

--
2.43.0

On Monday, 19 January 2026 at 04:50:05 UTC+5:30 syzbot wrote:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}'
token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function
returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=100fdb9a580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to apply patch after dry run:
patching file net/netfilter/nf_conntrack_core.c
Hunk #1 succeeded at 1551 (offset -1 lines).
patching file net/netfilter/nf_conntrack_core.c
Hunk #1 FAILED at 1552.
1 out of 1 hunk FAILED -- saving rejects to file net/netfilter/nf_conntrack_core.c.rej
patching file net/netfilter/nf_conntrack_core.c
Hunk #1 FAILED at 1552.
1 out of 1 hunk FAILED -- saving rejects to file net/netfilter/nf_conntrack_core.c.rej
patching file net/netfilter/nf_conntrack_core.c
Hunk #1 FAILED at 1552.
1 out of 1 hunk FAILED -- saving rejects to file net/netfilter/nf_conntrack_core.c.rej
patching file net/netfilter/nf_conntrack_core.c
Hunk #1 FAILED at 1552.
1 out of 1 hunk FAILED -- saving rejects to file net/netfilter/nf_conntrack_core.c.rej

Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=112153fa580000

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Private message regarding: [syzbot] [wireless?] WARNING in drv_get_tsf (2)
Author: kapoor...@gmail.com

#syz test

From 0cd0a5cff75a12d3cf1fa0675950ef0dcc647799 Mon Sep 17 00:00:00 2001
From: Arnav Kapoor <kapoor...@gmail.com>

--
2.43.0

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=112153fa580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]

Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419

compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=17a44b9a580000

[syzbot]

On Monday, 19 January 2026 at 05:09:05 UTC+5:30 syzbot wrote:

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}'
token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function
returning non-void [-Werror=return-type]


Tested on:

commit: e84d9601 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=17a44b9a580000

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-...@vger.kernel.org, syzkall...@googlegroups.com.

***

Subject: Private message regarding: Forwarded: Private message regarding: [syzbot] [wireless?] WARNING in drv_get_tsf (2)

kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for
Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=17a44b9a580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

net/mac80211/debugfs_netdev.c:662:70: error: expected ')' before 'return'
net/mac80211/debugfs_netdev.c:665:1: error: expected expression before '}' token
net/mac80211/debugfs_netdev.c:664:80: error: expected ';' before '}' token
net/mac80211/debugfs_netdev.c:665:1: error: no return statement in function returning non-void [-Werror=return-type]


Tested on:

commit: 24d479d2 Linux 6.19-rc6

git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=14040d22580000

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to apply patch:
checking file net/mac80211/debugfs_netdev.c
patch: **** malformed patch at line 14: diff --git a/net/mac80211/debugfs_netdev.c b/net/mac80211/debugfs_netdev.c

Tested on:

commit: 24d479d2 Linux 6.19-rc6
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=ae589cd0a6acd9be
dashboard link: https://syzkaller.appspot.com/bug?extid=2cecf0e829ae2219d419
compiler:

patch: https://syzkaller.appspot.com/x/patch.diff?x=167153fa580000