[syzbot] [bpf?] [net?] possible deadlock in sock_map_unref

[syzbot <syzbot+850ca6a3ba35c8699832@syzkaller.appspotmail.com>]

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=1363aaa9180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6fb1be60a193d440
dashboard link: https://syzkaller.appspot.com/bug?extid=850ca6a3ba35c8699832
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: syzbot+850ca6a3ba35c8699832@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-05271-gf99c5f563c17 #0 Not tainted
------------------------------------------------------
syz-executor.4/21902 is trying to acquire lock:
ffff88804ec83bf0 (clock-AF_UNIX){++..}-{2:2}, at: sock_map_del_link net/core/sock_map.c:163 [inline]
ffff88804ec83bf0 (clock-AF_UNIX){++..}-{2:2}, at: sock_map_unref+0x442/0x5e0 net/core/sock_map.c:180

but task is already holding lock:
ffff888066451200 (&stab->lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888066451200 (&stab->lock){+.-.}-{2:2}, at: sock_map_update_common+0x1b6/0x5b0 net/core/sock_map.c:490

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&stab->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_map_delete net/core/sock_map.c:414 [inline]
       sock_map_delete_elem+0x97/0x140 net/core/sock_map.c:446
       0xffffffffa00048e6
       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
       __bpf_prog_put_noref+0xd7/0x310 kernel/bpf/syscall.c:2244
       bpf_prog_put_deferred+0x2f3/0x3e0 kernel/bpf/syscall.c:2270
       __bpf_prog_put kernel/bpf/syscall.c:2282 [inline]
       bpf_prog_put+0x264/0x2a0 kernel/bpf/syscall.c:2289
       psock_set_prog include/linux/skmsg.h:475 [inline]
       sk_psock_stop_strp net/core/skmsg.c:1156 [inline]
       sk_psock_drop+0xe0/0x500 net/core/skmsg.c:841
       sk_psock_put include/linux/skmsg.h:459 [inline]
       sock_map_close+0x209/0x2d0 net/core/sock_map.c:1648
       unix_release+0x85/0xc0 net/unix/af_unix.c:1048
       __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 (clock-AF_UNIX){++..}-{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_write_lock_bh include/linux/rwlock_api_smp.h:202 [inline]
       _raw_write_lock_bh+0x35/0x50 kernel/locking/spinlock.c:334
       sock_map_del_link net/core/sock_map.c:163 [inline]
       sock_map_unref+0x442/0x5e0 net/core/sock_map.c:180
       sock_map_update_common+0x4f0/0x5b0 net/core/sock_map.c:503
       sock_map_update_elem_sys+0x55f/0x910 net/core/sock_map.c:579
       map_update_elem+0x53a/0x6f0 kernel/bpf/syscall.c:1641
       __sys_bpf+0x76f/0x810 kernel/bpf/syscall.c:5619
       __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(&stab->lock);
                               lock(clock-AF_UNIX);
                               lock(&stab->lock);
  lock(clock-AF_UNIX);

 *** DEADLOCK ***

3 locks held by syz-executor.4/21902:
 #0: ffff88804ec85a58 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1671 [inline]
 #0: ffff88804ec85a58 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_sk_acquire net/core/sock_map.c:117 [inline]
 #0: ffff88804ec85a58 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_update_elem_sys+0x1cc/0x910 net/core/sock_map.c:575
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: sock_map_sk_acquire net/core/sock_map.c:118 [inline]
 #1: ffffffff8e131920 (rcu_read_lock){....}-{1:2}, at: sock_map_update_elem_sys+0x1d8/0x910 net/core/sock_map.c:575
 #2: ffff888066451200 (&stab->lock){+.-.}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #2: ffff888066451200 (&stab->lock){+.-.}-{2:2}, at: sock_map_update_common+0x1b6/0x5b0 net/core/sock_map.c:490

stack backtrace:
CPU: 1 PID: 21902 Comm: syz-executor.4 Not tainted 6.8.0-syzkaller-05271-gf99c5f563c17 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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_write_lock_bh include/linux/rwlock_api_smp.h:202 [inline]
 _raw_write_lock_bh+0x35/0x50 kernel/locking/spinlock.c:334
 sock_map_del_link net/core/sock_map.c:163 [inline]
 sock_map_unref+0x442/0x5e0 net/core/sock_map.c:180
 sock_map_update_common+0x4f0/0x5b0 net/core/sock_map.c:503
 sock_map_update_elem_sys+0x55f/0x910 net/core/sock_map.c:579
 map_update_elem+0x53a/0x6f0 kernel/bpf/syscall.c:1641
 __sys_bpf+0x76f/0x810 kernel/bpf/syscall.c:5619
 __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: 0033:0x7f9934c7de69
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:00007f9935a7c0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f9934dac120 RCX: 00007f9934c7de69
RDX: 0000000000000020 RSI: 0000000020000880 RDI: 0000000000000002
RBP: 00007f9934cca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f9934dac120 R15: 00007fffdd7d6668
 </TASK>


---
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