* [PATCH] netlink: fix skb refcount leak when dump start fails
@ 2026-05-28 7:36 Wentao Liang
2026-05-28 8:04 ` Kuniyuki Iwashima
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Wentao Liang @ 2026-05-28 7:36 UTC (permalink / raw)
To: David S . Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni
Cc: Simon Horman, Kuniyuki Iwashima, Kees Cook, Feng Yang,
Wentao Liang, netdev, linux-kernel, stable
__netlink_dump_start() takes an extra reference on the received skb
via refcount_inc(&skb->users) before storing it in cb->skb for the
dump callback to consume. If the subsequent netlink_dump() call fails
(line 2440), the dump was never started so the completion callback
that would normally release cb->skb will never be invoked.
In this case, the function returns the error directly without calling
kfree_skb(skb) to release the extra reference taken at entry.
Add kfree_skb(skb) before returning when netlink_dump() fails, so the
skb reference is properly released.
Fixes: b44d211e166b ("netlink: handle errors from netlink_dump()")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
---
net/netlink/af_netlink.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 2aeb0680807d..d904c1aad35d 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2441,8 +2441,10 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
sock_put(sk);
- if (ret)
+ if (ret) {
+ kfree_skb(skb);
return ret;
+ }
/* We successfully started a dump, by returning -EINTR we
* signal not to send ACK even if it was requested.
--
2.34.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] netlink: fix skb refcount leak when dump start fails
2026-05-28 7:36 [PATCH] netlink: fix skb refcount leak when dump start fails Wentao Liang
@ 2026-05-28 8:04 ` Kuniyuki Iwashima
2026-05-28 8:08 ` Jiayuan Chen
2026-05-28 14:47 ` [syzbot ci] " syzbot ci
2 siblings, 0 replies; 4+ messages in thread
From: Kuniyuki Iwashima @ 2026-05-28 8:04 UTC (permalink / raw)
To: Wentao Liang
Cc: David S . Miller, Eric Dumazet, Jakub Kicinski, Paolo Abeni,
Simon Horman, Kees Cook, Feng Yang, netdev, linux-kernel, stable
On Thu, May 28, 2026 at 12:36 AM Wentao Liang <vulab@iscas.ac.cn> wrote:
>
> __netlink_dump_start() takes an extra reference on the received skb
> via refcount_inc(&skb->users) before storing it in cb->skb for the
> dump callback to consume. If the subsequent netlink_dump() call fails
> (line 2440), the dump was never started so the completion callback
> that would normally release cb->skb will never be invoked.
>
> In this case, the function returns the error directly without calling
> kfree_skb(skb) to release the extra reference taken at entry.
>
> Add kfree_skb(skb) before returning when netlink_dump() fails, so the
> skb reference is properly released.
Isn't consume_skb() in netlink_unicast_kernel() the one to free skb ?
>
> Fixes: b44d211e166b ("netlink: handle errors from netlink_dump()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
> ---
> net/netlink/af_netlink.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 2aeb0680807d..d904c1aad35d 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -2441,8 +2441,10 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
>
> sock_put(sk);
>
> - if (ret)
> + if (ret) {
> + kfree_skb(skb);
> return ret;
> + }
>
> /* We successfully started a dump, by returning -EINTR we
> * signal not to send ACK even if it was requested.
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] netlink: fix skb refcount leak when dump start fails
2026-05-28 7:36 [PATCH] netlink: fix skb refcount leak when dump start fails Wentao Liang
2026-05-28 8:04 ` Kuniyuki Iwashima
@ 2026-05-28 8:08 ` Jiayuan Chen
2026-05-28 14:47 ` [syzbot ci] " syzbot ci
2 siblings, 0 replies; 4+ messages in thread
From: Jiayuan Chen @ 2026-05-28 8:08 UTC (permalink / raw)
To: Wentao Liang, David S . Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni
Cc: Simon Horman, Kuniyuki Iwashima, Kees Cook, Feng Yang, netdev,
linux-kernel, stable
On 5/28/26 3:36 PM, Wentao Liang wrote:
> __netlink_dump_start() takes an extra reference on the received skb
> via refcount_inc(&skb->users) before storing it in cb->skb for the
> dump callback to consume. If the subsequent netlink_dump() call fails
> (line 2440), the dump was never started so the completion callback
> that would normally release cb->skb will never be invoked.
>
> In this case, the function returns the error directly without calling
> kfree_skb(skb) to release the extra reference taken at entry.
>
> Add kfree_skb(skb) before returning when netlink_dump() fails, so the
> skb reference is properly released.
>
> Fixes: b44d211e166b ("netlink: handle errors from netlink_dump()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
> ---
> net/netlink/af_netlink.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index 2aeb0680807d..d904c1aad35d 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -2441,8 +2441,10 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
>
> sock_put(sk);
>
> - if (ret)
> + if (ret) {
> + kfree_skb(skb);
> return ret;
> + }
>
> /* We successfully started a dump, by returning -EINTR we
> * signal not to send ACK even if it was requested.
static int netlink_release(struct socket *sock) {
.......
/* Terminate any outstanding dump */
if (nlk->cb_running) {
if (nlk->cb.done)
nlk->cb.done(&nlk->cb);
module_put(nlk->cb.module);
kfree_skb(nlk->cb.skb); <---- freed here
WRITE_ONCE(nlk->cb_running, false);
}
......
}
^ permalink raw reply [flat|nested] 4+ messages in thread
* [syzbot ci] Re: netlink: fix skb refcount leak when dump start fails
2026-05-28 7:36 [PATCH] netlink: fix skb refcount leak when dump start fails Wentao Liang
2026-05-28 8:04 ` Kuniyuki Iwashima
2026-05-28 8:08 ` Jiayuan Chen
@ 2026-05-28 14:47 ` syzbot ci
2 siblings, 0 replies; 4+ messages in thread
From: syzbot ci @ 2026-05-28 14:47 UTC (permalink / raw)
To: davem, edumazet, horms, kees, kuba, kuniyu, linux-kernel, netdev,
pabeni, stable, vulab, yangfeng
Cc: syzbot, syzkaller-bugs
syzbot ci has tested the following series
[v1] netlink: fix skb refcount leak when dump start fails
https://lore.kernel.org/all/20260528073614.1169858-1-vulab@iscas.ac.cn
* [PATCH] netlink: fix skb refcount leak when dump start fails
and found the following issues:
* KASAN: slab-use-after-free Read in nl80211_prepare_wdev_dump
* KASAN: slab-use-after-free Read in xfrm_dump_sa_done
* KASAN: slab-use-after-free Write in sk_skb_reason_drop
Full report is available here:
https://ci.syzbot.org/series/8ed6f41d-0d02-4f1f-a7be-cc639c2b4cfd
***
KASAN: slab-use-after-free Read in nl80211_prepare_wdev_dump
tree: net
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
base: 18014147d3ee7831dce53fe65d7fc8d428b02552
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/90c5185d-0dad-4c34-a563-4253ebb12eb2/config
syz repro: https://ci.syzbot.org/findings/0ad9835c-f631-4240-a3ad-2610bca3de33/syz_repro
==================================================================
BUG: KASAN: slab-use-after-free in __nlmsg_parse include/net/netlink.h:784 [inline]
BUG: KASAN: slab-use-after-free in nlmsg_parse_deprecated include/net/netlink.h:830 [inline]
BUG: KASAN: slab-use-after-free in nl80211_prepare_wdev_dump+0x634/0x680 net/wireless/nl80211.c:1245
Read of size 4 at addr ffff88816e172d80 by task syz.0.17/5814
CPU: 1 UID: 0 PID: 5814 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
__nlmsg_parse include/net/netlink.h:784 [inline]
nlmsg_parse_deprecated include/net/netlink.h:830 [inline]
nl80211_prepare_wdev_dump+0x634/0x680 net/wireless/nl80211.c:1245
nl80211_dump_station+0x186/0xdb0 net/wireless/nl80211.c:8216
genl_dumpit+0x10b/0x1b0 net/netlink/genetlink.c:1026
netlink_dump+0x702/0xe10 net/netlink/af_netlink.c:2325
netlink_recvmsg+0x690/0xa50 net/netlink/af_netlink.c:1976
sock_recvmsg_nosec net/socket.c:1137 [inline]
sock_recvmsg+0x172/0x1b0 net/socket.c:1159
__sys_recvfrom+0x240/0x3c0 net/socket.c:2315
__do_sys_recvfrom net/socket.c:2330 [inline]
__se_sys_recvfrom net/socket.c:2326 [inline]
__x64_sys_recvfrom+0xde/0x100 net/socket.c:2326
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd64155d68e
Code: 08 0f 85 a5 a8 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 80 00 00 00 00 48 83 ec 08
RSP: 002b:00007fd6424b5e88 EFLAGS: 00000246 ORIG_RAX: 000000000000002d
RAX: ffffffffffffffda RBX: 00007fd6424b76c0 RCX: 00007fd64155d68e
RDX: 0000000000001000 RSI: 00007fd6424b6000 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
R13: 00007fd6424b5f58 R14: 00007fd6424b6000 R15: 0000000000000000
</TASK>
Allocated by task 5813:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4569 [inline]
slab_alloc_node mm/slub.c:4898 [inline]
kmem_cache_alloc_node_noprof+0x384/0x690 mm/slub.c:4950
kmalloc_reserve net/core/skbuff.c:613 [inline]
__alloc_skb+0x27d/0x7d0 net/core/skbuff.c:713
netlink_sendmsg+0x5d4/0xb40 net/netlink/af_netlink.c:1869
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2698
___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
__sys_sendmsg net/socket.c:2784 [inline]
__do_sys_sendmsg net/socket.c:2789 [inline]
__se_sys_sendmsg net/socket.c:2787 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 5813:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
slab_free mm/slub.c:6250 [inline]
kfree+0x1c5/0x640 mm/slub.c:6565
skb_kfree_head net/core/skbuff.c:1075 [inline]
skb_free_head net/core/skbuff.c:1087 [inline]
skb_release_data+0x828/0xa60 net/core/skbuff.c:1114
skb_release_all net/core/skbuff.c:1189 [inline]
__kfree_skb+0x5d/0x210 net/core/skbuff.c:1203
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x764/0x8e0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2698
___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
__sys_sendmsg net/socket.c:2784 [inline]
__do_sys_sendmsg net/socket.c:2789 [inline]
__se_sys_sendmsg net/socket.c:2787 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff88816e172d80
which belongs to the cache skbuff_small_head of size 704
The buggy address is located 0 bytes inside of
freed 704-byte region [ffff88816e172d80, ffff88816e173040)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x16e170
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff888160415140 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800120012 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff888160415140 dead000000000100 dead000000000122
head: 0000000000000000 0000000800120012 00000000f5000000 0000000000000000
head: 057ff00000000002 ffffffffffffff01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5530, tgid 5530 (sshd), ts 47735478218, free_ts 34702748767
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1858
prep_new_page mm/page_alloc.c:1866 [inline]
get_page_from_freelist+0x24ba/0x2540 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3467
new_slab mm/slub.c:3525 [inline]
refill_objects+0x339/0x3d0 mm/slub.c:7271
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x321/0x720 mm/slub.c:4651
alloc_from_pcs mm/slub.c:4749 [inline]
slab_alloc_node mm/slub.c:4883 [inline]
kmem_cache_alloc_node_noprof+0x441/0x690 mm/slub.c:4950
kmalloc_reserve net/core/skbuff.c:613 [inline]
__alloc_skb+0x27d/0x7d0 net/core/skbuff.c:713
alloc_skb include/linux/skbuff.h:1383 [inline]
__tcp_send_ack+0xae/0x4f0 net/ipv4/tcp_output.c:4473
tcp_cleanup_rbuf net/ipv4/tcp.c:1612 [inline]
tcp_recvmsg_locked+0x2dfa/0x3720 net/ipv4/tcp.c:2916
tcp_recvmsg+0x205/0x7e0 net/ipv4/tcp.c:2945
sock_recvmsg_nosec net/socket.c:1137 [inline]
sock_recvmsg+0x155/0x1b0 net/socket.c:1159
sock_read_iter+0x251/0x320 net/socket.c:1229
new_sync_read fs/read_write.c:493 [inline]
vfs_read+0x582/0xa70 fs/read_write.c:574
ksys_read+0x150/0x270 fs/read_write.c:717
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
page last free pid 5059 tgid 5059 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1402 [inline]
__free_frozen_pages+0xbc7/0xd30 mm/page_alloc.c:2943
__slab_free+0x274/0x2c0 mm/slub.c:5612
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4569 [inline]
slab_alloc_node mm/slub.c:4898 [inline]
__do_kmalloc_node mm/slub.c:5294 [inline]
__kvmalloc_node_noprof+0x4d7/0x8a0 mm/slub.c:6832
seq_buf_alloc fs/seq_file.c:39 [inline]
seq_read_iter+0x202/0xe10 fs/seq_file.c:211
new_sync_read fs/read_write.c:493 [inline]
vfs_read+0x582/0xa70 fs/read_write.c:574
ksys_read+0x150/0x270 fs/read_write.c:717
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Memory state around the buggy address:
ffff88816e172c80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff88816e172d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88816e172d80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88816e172e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88816e172e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
***
KASAN: slab-use-after-free Read in xfrm_dump_sa_done
tree: net
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
base: 18014147d3ee7831dce53fe65d7fc8d428b02552
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/90c5185d-0dad-4c34-a563-4253ebb12eb2/config
syz repro: https://ci.syzbot.org/findings/53579ff8-1479-4e0c-ae08-2f1ea756ee1b/syz_repro
==================================================================
BUG: KASAN: slab-use-after-free in xfrm_dump_sa_done+0x54/0xd0 net/xfrm/xfrm_user.c:1491
Read of size 8 at addr ffff888167305398 by task syz.0.17/5812
CPU: 1 UID: 0 PID: 5812 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
xfrm_dump_sa_done+0x54/0xd0 net/xfrm/xfrm_user.c:1491
netlink_release+0x12c8/0x1ad0 net/netlink/af_netlink.c:768
__sock_release net/socket.c:722 [inline]
sock_close+0xc3/0x240 net/socket.c:1514
__fput+0x44f/0xa60 fs/file_table.c:510
task_work_run+0x1d9/0x270 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0xf3/0x4d0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe50bf9ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff8a02cc38 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fe50c217da0 RCX: 00007fe50bf9ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fe50c217da0 R08: 00007fe50c216038 R09: 0000000000000000
R10: 000000000003fdd4 R11: 0000000000000246 R12: 0000000000010018
R13: 00007fe50c215fac R14: 00007fe50c215fa8 R15: 00007fe50c215fa0
</TASK>
Allocated by task 5813:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
kasan_slab_alloc include/linux/kasan.h:253 [inline]
slab_post_alloc_hook mm/slub.c:4569 [inline]
slab_alloc_node mm/slub.c:4898 [inline]
kmem_cache_alloc_node_noprof+0x384/0x690 mm/slub.c:4950
__alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
netlink_sendmsg+0x5d4/0xb40 net/netlink/af_netlink.c:1869
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2698
___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
__sys_sendmsg net/socket.c:2784 [inline]
__do_sys_sendmsg net/socket.c:2789 [inline]
__se_sys_sendmsg net/socket.c:2787 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 5813:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
slab_free mm/slub.c:6250 [inline]
kmem_cache_free+0x182/0x650 mm/slub.c:6377
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x764/0x8e0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2698
___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
__sys_sendmsg net/socket.c:2784 [inline]
__do_sys_sendmsg net/socket.c:2789 [inline]
__se_sys_sendmsg net/socket.c:2787 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888167305380
which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 24 bytes inside of
freed 240-byte region [ffff888167305380, ffff888167305470)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x167304
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000040(head|node=1|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 057ff00000000040 ffff888160416dc0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800150015 00000000f5000000 0000000000000000
head: 057ff00000000040 ffff888160416dc0 dead000000000100 dead000000000122
head: 0000000000000000 0000000800150015 00000000f5000000 0000000000000000
head: 057ff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5813, tgid 5812 (syz.0.17), ts 64859679564, free_ts 63312613640
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1858
prep_new_page mm/page_alloc.c:1866 [inline]
get_page_from_freelist+0x24ba/0x2540 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3467
new_slab mm/slub.c:3525 [inline]
refill_objects+0x339/0x3d0 mm/slub.c:7271
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x321/0x720 mm/slub.c:4651
alloc_from_pcs mm/slub.c:4749 [inline]
slab_alloc_node mm/slub.c:4883 [inline]
kmem_cache_alloc_node_noprof+0x441/0x690 mm/slub.c:4950
__alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
netlink_sendmsg+0x5d4/0xb40 net/netlink/af_netlink.c:1869
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
____sys_sendmsg+0x972/0x9f0 net/socket.c:2698
___sys_sendmsg+0x2a5/0x360 net/socket.c:2752
__sys_sendmsg net/socket.c:2784 [inline]
__do_sys_sendmsg net/socket.c:2789 [inline]
__se_sys_sendmsg net/socket.c:2787 [inline]
__x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 15 tgid 15 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1402 [inline]
__free_frozen_pages+0xbc7/0xd30 mm/page_alloc.c:2943
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869
handle_softirqs+0x22a/0x840 kernel/softirq.c:622
run_ksoftirqd+0x36/0x60 kernel/softirq.c:1076
smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
kthread+0x389/0x470 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Memory state around the buggy address:
ffff888167305280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
ffff888167305300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888167305380: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888167305400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
ffff888167305480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
***
KASAN: slab-use-after-free Write in sk_skb_reason_drop
tree: net
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
base: 18014147d3ee7831dce53fe65d7fc8d428b02552
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/90c5185d-0dad-4c34-a563-4253ebb12eb2/config
syz repro: https://ci.syzbot.org/findings/c87569e1-d26e-4670-a17b-9f2f64a5af67/syz_repro
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
BUG: KASAN: slab-use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
BUG: KASAN: slab-use-after-free in __refcount_sub_and_test include/linux/refcount.h:389 [inline]
BUG: KASAN: slab-use-after-free in __refcount_dec_and_test include/linux/refcount.h:432 [inline]
BUG: KASAN: slab-use-after-free in refcount_dec_and_test include/linux/refcount.h:450 [inline]
BUG: KASAN: slab-use-after-free in skb_unref include/linux/skbuff.h:1292 [inline]
BUG: KASAN: slab-use-after-free in __sk_skb_reason_drop net/core/skbuff.c:1212 [inline]
BUG: KASAN: slab-use-after-free in sk_skb_reason_drop+0x37/0x110 net/core/skbuff.c:1240
Write of size 4 at addr ffff8881178efee4 by task syz.1.18/5873
CPU: 0 UID: 0 PID: 5873 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
__refcount_sub_and_test include/linux/refcount.h:389 [inline]
__refcount_dec_and_test include/linux/refcount.h:432 [inline]
refcount_dec_and_test include/linux/refcount.h:450 [inline]
skb_unref include/linux/skbuff.h:1292 [inline]
__sk_skb_reason_drop net/core/skbuff.c:1212 [inline]
sk_skb_reason_drop+0x37/0x110 net/core/skbuff.c:1240
kfree_skb_reason include/linux/skbuff.h:1322 [inline]
kfree_skb include/linux/skbuff.h:1331 [inline]
netlink_release+0x133a/0x1ad0 net/netlink/af_netlink.c:770
__sock_release net/socket.c:722 [inline]
sock_close+0xc3/0x240 net/socket.c:1514
__fput+0x44f/0xa60 fs/file_table.c:510
task_work_run+0x1d9/0x270 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0xf3/0x4d0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd4d139ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff722ecbf8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fff722ecce0 RCX: 00007fd4d139ce59
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 0000000000012825 R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b32e20000 R11: 0000000000000246 R12: 00007fff722ecd20
R13: 00007fd4d1615fac R14: 0000000000012859 R15: 00007fd4d1615fa0
</TASK>
Allocated by task 5874:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
unpoison_slab_object mm/kasan/common.c:340 [inline]
__kasan_mempool_unpoison_object+0xa3/0x130 mm/kasan/common.c:564
kasan_mempool_unpoison_object include/linux/kasan.h:391 [inline]
napi_skb_cache_get+0x3c8/0x780 net/core/skbuff.c:306
__alloc_skb+0x19a/0x7d0 net/core/skbuff.c:696
netlink_sendmsg+0x5d4/0xb40 net/netlink/af_netlink.c:1869
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
__sys_sendto+0x672/0x710 net/socket.c:2265
__do_sys_sendto net/socket.c:2272 [inline]
__se_sys_sendto net/socket.c:2268 [inline]
__x64_sys_sendto+0xde/0x100 net/socket.c:2268
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 5874:
kasan_save_stack mm/kasan/common.c:57 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
slab_free mm/slub.c:6250 [inline]
kmem_cache_free+0x182/0x650 mm/slub.c:6377
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x764/0x8e0 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
__sys_sendto+0x672/0x710 net/socket.c:2265
__do_sys_sendto net/socket.c:2272 [inline]
__se_sys_sendto net/socket.c:2268 [inline]
__x64_sys_sendto+0xde/0x100 net/socket.c:2268
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff8881178efe00
which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 228 bytes inside of
freed 240-byte region [ffff8881178efe00, ffff8881178efef0)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1178ee
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x17ff00000000040(head|node=0|zone=2|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 017ff00000000040 ffff888160416c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000800150015 00000000f5000000 0000000000000000
head: 017ff00000000040 ffff888160416c80 dead000000000122 0000000000000000
head: 0000000000000000 0000000800150015 00000000f5000000 0000000000000000
head: 017ff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5050, tgid 5050 (klogd), ts 75887265953, free_ts 75876344896
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1858
prep_new_page mm/page_alloc.c:1866 [inline]
get_page_from_freelist+0x24ba/0x2540 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab+0x77/0x660 mm/slub.c:3467
new_slab mm/slub.c:3525 [inline]
refill_objects+0x339/0x3d0 mm/slub.c:7271
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x321/0x720 mm/slub.c:4651
alloc_from_pcs mm/slub.c:4749 [inline]
slab_alloc_node mm/slub.c:4883 [inline]
kmem_cache_alloc_node_noprof+0x441/0x690 mm/slub.c:4950
__alloc_skb+0x1d0/0x7d0 net/core/skbuff.c:702
alloc_skb include/linux/skbuff.h:1383 [inline]
alloc_skb_with_frags+0xc8/0x760 net/core/skbuff.c:6743
sock_alloc_send_pskb+0x878/0x990 net/core/sock.c:2998
unix_dgram_sendmsg+0x460/0x18d0 net/unix/af_unix.c:2141
sock_sendmsg_nosec net/socket.c:787 [inline]
__sock_sendmsg net/socket.c:802 [inline]
__sys_sendto+0x672/0x710 net/socket.c:2265
__do_sys_sendto net/socket.c:2272 [inline]
__se_sys_sendto net/socket.c:2268 [inline]
__x64_sys_sendto+0xde/0x100 net/socket.c:2268
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 0 tgid 0 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1402 [inline]
__free_frozen_pages+0xbc7/0xd30 mm/page_alloc.c:2943
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869
handle_softirqs+0x22a/0x840 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0xca/0x220 kernel/softirq.c:735
irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
Memory state around the buggy address:
ffff8881178efd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881178efe00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881178efe80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
^
ffff8881178eff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8881178eff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
***
If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syzbot@syzkaller.appspotmail.com
---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.
To test a patch for this bug, please reply with `#syz test`
(should be on a separate line).
The patch should be attached to the email.
Note: arguments like custom git repos and branches are not supported.
^ permalink raw reply [flat|nested] 4+ messages in thread
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Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-05-28 7:36 [PATCH] netlink: fix skb refcount leak when dump start fails Wentao Liang
2026-05-28 8:04 ` Kuniyuki Iwashima
2026-05-28 8:08 ` Jiayuan Chen
2026-05-28 14:47 ` [syzbot ci] " syzbot ci
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