Re: [syzbot] [net?] WARNING in inet_sock_destruct (6)

[Kuniyuki Iwashima]

From: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>
Date: Sat, 14 Feb 2026 13:46:38 +0800
> On Fri, Feb 13, 2026 at 12:08:38PM +0800, syzbot wrote:
> 
> I identified this issue and submitted a fix before this syzbot report:
> https://lore.kernel.org/bpf/20250508062423.51978-1-jiayuan.chen@xxxxxxxxx/
> Unfortunately the patch was not accepted at the time.

The fix is not sufficient since sk->sk_forward_alloc is
still modified locklessly.

I'm releasing other related reports and going to send fix
shortly.


> 
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    192c0159402e Merge tag 'powerpc-7.0-1' of git://git.kernel..
> > git tree:       upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=17b8cc02580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=22c34f040954bbd1
> > dashboard link: https://syzkaller.appspot.com/bug?extid=5b3b7e51dda1be027b7a
> > compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1316a15a580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14140ffa580000
> > 
> > Downloadable assets:
> > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-192c0159.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/d1c911c7a5b8/vmlinux-192c0159.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/f9d4cfbb614a/bzImage-192c0159.xz
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+5b3b7e51dda1be027b7a@xxxxxxxxxxxxxxxxxxxxxxxxx
> > 
> > ------------[ cut here ]------------
> > sk->sk_forward_alloc
> > WARNING: net/ipv4/af_inet.c:157 at inet_sock_destruct+0x653/0x800 net/ipv4/af_inet.c:157, CPU#0: ksoftirqd/0/15
> > Modules linked in:
> > CPU: 0 UID: 0 PID: 15 Comm: ksoftirqd/0 Not tainted syzkaller #0 PREEMPT(full) 
> > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
> > RIP: 0010:inet_sock_destruct+0x653/0x800 net/ipv4/af_inet.c:157
> > Code: b4 4f ff e9 06 fd ff ff e8 aa 25 10 f8 90 0f 0b 90 e9 35 fe ff ff e8 9c 25 10 f8 90 0f 0b 90 e9 c5 fe ff ff e8 8e 25 10 f8 90 <0f> 0b 90 e9 04 ff ff ff e8 80 25 10 f8 90 0f 0b 90 e9 65 fe ff ff
> > RSP: 0018:ffffc90000127bb0 EFLAGS: 00010246
> > RAX: 0000000000000000 RBX: ffff888100796300 RCX: ffffffff89f71e97
> > RDX: ffff88801dec4900 RSI: ffffffff89f71f92 RDI: ffff88801dec4900
> > RBP: 0000000000000090 R08: 0000000000000005 R09: 0000000000000000
> > R10: 0000000000000090 R11: 00000000000075f9 R12: ffff888100796300
> > R13: ffff888100796390 R14: ffffffff81ed1d7d R15: 0000000000000004
> > FS:  0000000000000000(0000) GS:ffff8880d65b3000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007ffe39b75ff4 CR3: 000000000e396000 CR4: 0000000000352ef0
> > Call Trace:
> >  <TASK>
> >  __sk_destruct+0x85/0xbb0 net/core/sock.c:2350
> >  rcu_do_batch kernel/rcu/tree.c:2617 [inline]
> >  rcu_core+0x5a2/0x10d0 kernel/rcu/tree.c:2869
> >  handle_softirqs+0x1ea/0x910 kernel/softirq.c:622
> >  run_ksoftirqd kernel/softirq.c:1063 [inline]
> >  run_ksoftirqd+0x38/0x60 kernel/softirq.c:1055
> >  smpboot_thread_fn+0x3d3/0xaa0 kernel/smpboot.c:160
> >  kthread+0x370/0x450 kernel/kthread.c:467
> >  ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
> >  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> >  </TASK>
> >