[v6.1] WARNING in sk_msg_free

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e4f7d8be268e Linux 6.1.182
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15faec79580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=acd74cdc1f524d077fbc
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/156843a60452/disk-e4f7d8be.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/719d532a0151/vmlinux-e4f7d8be.xz
kernel image: https://storage.googleapis.com/syzbot-assets/12160bc2f9ec/bzImage-e4f7d8be.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+acd74c...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 6759 at include/linux/skmsg.h:142 sk_msg_check_to_free include/linux/skmsg.h:142 [inline]
WARNING: CPU: 0 PID: 6759 at include/linux/skmsg.h:142 __sk_msg_free net/core/skmsg.c:204 [inline]
WARNING: CPU: 0 PID: 6759 at include/linux/skmsg.h:142 sk_msg_free+0x179/0x300 net/core/skmsg.c:220
Modules linked in:
CPU: 0 PID: 6759 Comm: syz.1.553 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:sk_msg_check_to_free include/linux/skmsg.h:142 [inline]
RIP: 0010:__sk_msg_free net/core/skmsg.c:204 [inline]
RIP: 0010:sk_msg_free+0x179/0x300 net/core/skmsg.c:220
Code: 74 23 e8 2a 03 37 f9 44 01 ed 45 85 ff 0f 84 df 00 00 00 e8 19 03 37 f9 49 89 de 48 8b 74 24 10 e9 21 ff ff ff e8 07 03 37 f9 <0f> 0b 48 8b 44 24 18 0f b6 04 18 84 c0 0f 85 95 00 00 00 48 8b 04
RSP: 0018:ffffc9000d0b7958 EFLAGS: 00010283
RAX: ffffffff884b2b19 RBX: dffffc0000000000 RCX: 0000000000080000
RDX: ffffc900051e1000 RSI: 000000000000d0fd RDI: 000000000000d0fe
RBP: 0000000000000000 R08: ffff88801b28a28f R09: ffff88801b28a270
R10: dffffc0000000000 R11: ffffed1003651452 R12: 0000000000000002
R13: 0000000000007fff R14: 0000000000000002 R15: 0000000000008000
FS: 00007fcd66b4f6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f54bb1eb7c0 CR3: 0000000053eb5000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
espintcp_close+0x116/0x150 net/xfrm/espintcp.c:541
inet_release+0x139/0x180 net/ipv4/af_inet.c:430
__sock_release net/socket.c:654 [inline]
sock_close+0xbf/0x210 net/socket.c:1400
__fput+0x20a/0x8b0 fs/file_table.c:320
task_work_run+0x1d0/0x260 kernel/task_work.c:203
get_signal+0x118d/0x1340 kernel/signal.c:2657
arch_do_signal_or_restart+0xc4/0x1310 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fcd65b9e0d9
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:00007fcd66b4f028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: 000000000000fffd RBX: 00007fcd65e25fa0 RCX: 00007fcd65b9e0d9
RDX: 000000000000fffd RSI: 0000200000000600 RDI: 0000000000000004
RBP: 00007fcd65c35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcd65e26038 R14: 00007fcd65e25fa0 R15: 00007ffd67d338a8
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: e4f7d8be268e Linux 6.1.182
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=17421c79580000

kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=acd74cdc1f524d077fbc
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12615149580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11158ac6580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/156843a60452/disk-e4f7d8be.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/719d532a0151/vmlinux-e4f7d8be.xz
kernel image: https://storage.googleapis.com/syzbot-assets/12160bc2f9ec/bzImage-e4f7d8be.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+acd74c...@syzkaller.appspotmail.com

------------[ cut here ]------------

WARNING: CPU: 0 PID: 4820 at include/linux/skmsg.h:142 sk_msg_check_to_free include/linux/skmsg.h:142 [inline]
WARNING: CPU: 0 PID: 4820 at include/linux/skmsg.h:142 __sk_msg_free net/core/skmsg.c:204 [inline]
WARNING: CPU: 0 PID: 4820 at include/linux/skmsg.h:142 sk_msg_free+0x179/0x300 net/core/skmsg.c:220
Modules linked in:
CPU: 0 PID: 4820 Comm: syz.1.137 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:sk_msg_check_to_free include/linux/skmsg.h:142 [inline]
RIP: 0010:__sk_msg_free net/core/skmsg.c:204 [inline]
RIP: 0010:sk_msg_free+0x179/0x300 net/core/skmsg.c:220
Code: 74 23 e8 2a 03 37 f9 44 01 ed 45 85 ff 0f 84 df 00 00 00 e8 19 03 37 f9 49 89 de 48 8b 74 24 10 e9 21 ff ff ff e8 07 03 37 f9 <0f> 0b 48 8b 44 24 18 0f b6 04 18 84 c0 0f 85 95 00 00 00 48 8b 04

RSP: 0018:ffffc900052df958 EFLAGS: 00010293
RAX: ffffffff884b2b19 RBX: dffffc0000000000 RCX: ffff88802abd1e00
RDX: 0000000000000000 RSI: 0000000000008000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88807c6d128f R09: ffff88807c6d1270
R10: dffffc0000000000 R11: ffffed100f8da252 R12: 0000000000000002

R13: 0000000000007fff R14: 0000000000000002 R15: 0000000000008000

FS: 00007fb4573dd6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00002317b8054000 CR3: 000000005b4b7000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
espintcp_close+0x116/0x150 net/xfrm/espintcp.c:541
inet_release+0x139/0x180 net/ipv4/af_inet.c:430
__sock_release net/socket.c:654 [inline]
sock_close+0xbf/0x210 net/socket.c:1400
__fput+0x20a/0x8b0 fs/file_table.c:320
task_work_run+0x1d0/0x260 kernel/task_work.c:203
get_signal+0x118d/0x1340 kernel/signal.c:2657
arch_do_signal_or_restart+0xc4/0x1310 arch/x86/kernel/signal.c:871
exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7fb457d9e0d9

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:00007fb4573dd028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: 000000000000fffd RBX: 00007fb458026090 RCX: 00007fb457d9e0d9

RDX: 000000000000fffd RSI: 0000200000000600 RDI: 0000000000000004

RBP: 00007fb457e35024 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fb458026128 R14: 00007fb458026090 R15: 00007ffe4de35128
</TASK>


---
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