Re: [syzbot] [bpf?] [net?] WARNING in sock_map_del_link

[Xin Liu]

On 4/14/23 2:42 AM, Daniel Borkmann wrote:
> On 4/13/23 5:33 PM, syzbot wrote:
> > Hello,
> > 
> > syzbot found the following issue on:
> > 
> > HEAD commit:    d319f344561d mm: Fix copy_from_user_nofault().
> > git tree:       bpf-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=15930c9dc80000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=78c9d875f0a80d33
> > dashboard link: https://syzkaller.appspot.com/bug?extid=49f6cef45247ff249498
> > compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> > 
> > Unfortunately, I don't have any reproducer for this issue yet.
> > 
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/229f3623b7df/disk-d319f344.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/6da0db75c9aa/vmlinux-d319f344.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/01f022fb9a13/bzImage-d319f344.xz
> > 
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+49f6cef45247ff249498@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> Xin, fyi, given we're currently prepping bpf-next pr we unfortunately had to revert commit
> ed17aa92dc56 ("bpf, sockmap: fix deadlocks in the sockhash and sockmap") which is causing
> this new syzkaller splat. There's another one in the syzkaller queue we've been made
> aware of which bisected to earlier mentioned commit.
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=8c5c2a4898e3d6bad86e29d471e023c8a19ba799
> 
> > ------------[ cut here ]------------
> > WARNING: CPU: 1 PID: 7921 at kernel/softirq.c:376 __local_bh_enable_ip+0xbe/0x130 kernel/softirq.c:376
> > Modules linked in:
> > CPU: 1 PID: 7921 Comm: syz-executor.4 Not tainted 6.2.0-syzkaller-13249-gd319f344561d #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
> > RIP: 0010:__local_bh_enable_ip+0xbe/0x130 kernel/softirq.c:376
> > Code: 45 bf 01 00 00 00 e8 b1 44 0a 00 e8 9c 41 3d 00 fb 65 8b 05 2c 61 b5 7e 85 c0 74 58 5b 5d c3 65 8b 05 12 2f b4 7e 85 c0 75 a2 <0f> 0b eb 9e e8 e9 41 3d 00 eb 9f 48 89 ef e8 ff 30 18 00 eb a8 0f
> > RSP: 0018:ffffc90007bffbe8 EFLAGS: 00010046
> > RAX: 0000000000000000 RBX: 0000000000000201 RCX: 1ffffffff1cf0736
> > RDX: 0000000000000000 RSI: 0000000000000201 RDI: ffffffff882bf40a
> > RBP: ffffffff882bf40a R08: 0000000000000000 R09: ffff88801cc6327b
> > R10: ffffed100398c64f R11: 1ffffffff21917f0 R12: ffff88801cc63268
> > R13: ffff88801cc63268 R14: ffff8880188ef500 R15: 0000000000000000
> > FS:  00007f378f724700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 00007fbbc57831b8 CR3: 00000000210ad000 CR4: 00000000003506e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >   <TASK>
> >   spin_unlock_bh include/linux/spinlock.h:395 [inline]
> >   sock_map_del_link+0x2ea/0x510 net/core/sock_map.c:165
> >   sock_map_unref+0xb0/0x1d0 net/core/sock_map.c:184
> >   sock_hash_delete_elem+0x1ec/0x2a0 net/core/sock_map.c:945
> >   map_delete_elem kernel/bpf/syscall.c:1536 [inline]
> >   __sys_bpf+0x2edc/0x53e0 kernel/bpf/syscall.c:5053
> >   __do_sys_bpf kernel/bpf/syscall.c:5166 [inline]
> >   __se_sys_bpf kernel/bpf/syscall.c:5164 [inline]
> >   __x64_sys_bpf+0x79/0xc0 kernel/bpf/syscall.c:5164
> >   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >   do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
> >   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > RIP: 0033:0x7f378ea8c169
> > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
> > RSP: 002b:00007f378f724168 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> > RAX: ffffffffffffffda RBX: 00007f378ebabf80 RCX: 00007f378ea8c169
> > RDX: 0000000000000020 RSI: 0000000020000140 RDI: 0000000000000003
> > RBP: 00007f378eae7ca1 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> > R13: 00007ffe9737aebf R14: 00007f378f724300 R15: 0000000000022000
> >   </TASK>
> > 
> > 
> > ---
> > This report is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> > 
> > syzbot will keep track of this issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> > 

I did miss some bh lock processing when deleting links, and I'll be
combing the use of sockhash locks recently.
Thanks.