Subject: [syzbot] [bpf?] [net?] possible deadlock in sk_psock_drop

From: syzbot <[email-masked]>
Date: Tue, 26 Mar 2024 12:01:24 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    f99c5f563c17 Merge tag 'nf-24-03-21' of git://git.kernel.o..
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=15a444b1180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=59286e53e6c7d1921164
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/65d3f3eb786e/disk-f99c5f56.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/799cf7f28ff8/vmlinux-f99c5f56.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ab26c60c3845/bzImage-f99c5f56.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-05271-gf99c5f563c17 #0 Not tainted
------------------------------------------------------
syz-executor.4/21268 is trying to acquire lock:
ffff88802248b238 (&psock->ingress_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff88802248b238 (&psock->ingress_lock){+...}-{2:2}, at: sk_psock_stop net/core/skmsg.c:802 [inline]
ffff88802248b238 (&psock->ingress_lock){+...}-{2:2}, at: sk_psock_drop+0x2fb/0x500 net/core/skmsg.c:846

but task is already holding lock:
ffff88802c949620 (&htab->buckets[i].lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff88802c949620 (&htab->buckets[i].lock){+.-.}-{2:2}, at: sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&htab->buckets[i].lock){+.-.}-{2:2}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939
       0xffffffffa000095f
       bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
       __bpf_prog_run include/linux/filter.h:657 [inline]
       bpf_prog_run include/linux/filter.h:664 [inline]
       __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
       bpf_trace_run2+0x204/0x420 kernel/trace/bpf_trace.c:2420
       trace_kfree include/trace/events/kmem.h:94 [inline]
       kfree+0x291/0x380 mm/slub.c:4396
       sk_psock_cork_free include/linux/skmsg.h:430 [inline]
       sk_psock_stop+0xc5/0x110 net/core/skmsg.c:804
       sock_map_close+0x1b2/0x2d0 net/core/sock_map.c:1645
       inet_release+0x17d/0x200 net/ipv4/af_inet.c:437
       __sock_release net/socket.c:659 [inline]
       sock_close+0xbc/0x240 net/socket.c:1421
       __fput+0x429/0x8a0 fs/file_table.c:423
       __do_sys_close fs/open.c:1557 [inline]
       __se_sys_close fs/open.c:1542 [inline]
       __x64_sys_close+0x7f/0x110 fs/open.c:1542
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #0 (&psock->ingress_lock){+...}-{2:2}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
       _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       sk_psock_stop net/core/skmsg.c:802 [inline]
       sk_psock_drop+0x2fb/0x500 net/core/skmsg.c:846
       sock_hash_delete_elem+0x27e/0x300 net/core/sock_map.c:943
       map_delete_elem+0x464/0x5e0 kernel/bpf/syscall.c:1696
       __sys_bpf+0x598/0x810 kernel/bpf/syscall.c:5622
       __do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
       __se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
       __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&htab->buckets[i].lock);
                               lock(&psock->ingress_lock);
                               lock(&htab->buckets[i].lock);
  lock(&psock->ingress_lock);

 *** DEADLOCK ***

2 locks held by syz-executor.4/21268:
 #0: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #0: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
 #0: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: map_delete_elem+0x388/0x5e0 kernel/bpf/syscall.c:1695
 #1: ffff88802c949620 (&htab->buckets[i].lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #1: ffff88802c949620 (&htab->buckets[i].lock){+.-.}-{2:2}, at: sock_hash_delete_elem+0xb0/0x300 net/core/sock_map.c:939

stack backtrace:
CPU: 1 PID: 21268 Comm: syz-executor.4 Not tainted 6.8.0-syzkaller-05271-gf99c5f563c17 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x35/0x50 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 sk_psock_stop net/core/skmsg.c:802 [inline]
 sk_psock_drop+0x2fb/0x500 net/core/skmsg.c:846
 sock_hash_delete_elem+0x27e/0x300 net/core/sock_map.c:943
 map_delete_elem+0x464/0x5e0 kernel/bpf/syscall.c:1696
 __sys_bpf+0x598/0x810 kernel/bpf/syscall.c:5622
 __do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
 __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5736
 do_syscall_64+0xfb/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f008787dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f00885cd0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f00879abf80 RCX: 00007f008787dda9
RDX: 0000000000000020 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00007f00878ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f00879abf80 R15: 00007fff30ed4838
 </TASK>

---
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