Re: [syzbot] [bpf?] [net?] possible deadlock in __sock_map_delete

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    ed30a4a51bb1 Linux 6.9-rc5
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15124c3b180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=545d4b3e07d6ccbc
dashboard link: https://syzkaller.appspot.com/bug?extid=a4ed4041b9bea8177ac3
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=102d66bf180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10107f67180000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-ed30a4a5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c62dd6fbdae1/vmlinux-ed30a4a5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2ee0879390c1/bzImage-ed30a4a5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a4ed4041b9bea8177ac3@xxxxxxxxxxxxxxxxxxxxxxxxx

============================================
WARNING: possible recursive locking detected
6.9.0-rc5-syzkaller #0 Not tainted
--------------------------------------------
syz-executor381/5177 is trying to acquire lock:
ffff888027aca200 (&stab->lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888027aca200 (&stab->lock){+...}-{2:2}, at: __sock_map_delete+0x43/0xe0 net/core/sock_map.c:417

but task is already holding lock:
ffff888027acaa00 (&stab->lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888027acaa00 (&stab->lock){+...}-{2:2}, at: sock_map_update_common+0x197/0x870 net/core/sock_map.c:493

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&stab->lock);
  lock(&stab->lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

5 locks held by syz-executor381/5177:
 #0: ffff88802f6ad258 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1671 [inline]
 #0: ffff88802f6ad258 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_sk_acquire net/core/sock_map.c:117 [inline]
 #0: ffff88802f6ad258 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_update_elem_sys+0x1b6/0x570 net/core/sock_map.c:578
 #1: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #1: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
 #1: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: sock_map_sk_acquire net/core/sock_map.c:118 [inline]
 #1: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: sock_map_update_elem_sys+0x1d8/0x570 net/core/sock_map.c:578
 #2: ffff888027acaa00 (&stab->lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #2: ffff888027acaa00 (&stab->lock){+...}-{2:2}, at: sock_map_update_common+0x197/0x870 net/core/sock_map.c:493
 #3: ffff88801a940290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
 #3: ffff88801a940290 (&psock->link_lock){+...}-{2:2}, at: sock_map_del_link net/core/sock_map.c:145 [inline]
 #3: ffff88801a940290 (&psock->link_lock){+...}-{2:2}, at: sock_map_unref+0xbf/0x6e0 net/core/sock_map.c:180
 #4: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
 #4: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
 #4: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2380 [inline]
 #4: ffffffff8d7b0e20 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0xe4/0x420 kernel/trace/bpf_trace.c:2420

stack backtrace:
CPU: 3 PID: 5177 Comm: syz-executor381 Not tainted 6.9.0-rc5-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
 check_deadlock kernel/locking/lockdep.c:3062 [inline]
 validate_chain kernel/locking/lockdep.c:3856 [inline]
 __lock_acquire+0x20e6/0x3b30 kernel/locking/lockdep.c:5137
 lock_acquire kernel/locking/lockdep.c:5754 [inline]
 lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5719
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
 _raw_spin_lock_bh+0x33/0x40 kernel/locking/spinlock.c:178
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 __sock_map_delete+0x43/0xe0 net/core/sock_map.c:417
 sock_map_delete_elem+0xb5/0x100 net/core/sock_map.c:449
 ___bpf_prog_run+0x3e51/0xabd0 kernel/bpf/core.c:1997
 __bpf_prog_run32+0xc1/0x100 kernel/bpf/core.c:2236
 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+0x151/0x420 kernel/trace/bpf_trace.c:2420
 trace_kfree include/trace/events/kmem.h:94 [inline]
 kfree+0x225/0x390 mm/slub.c:4377
 sk_psock_free_link include/linux/skmsg.h:421 [inline]
 sock_map_del_link net/core/sock_map.c:158 [inline]
 sock_map_unref+0x392/0x6e0 net/core/sock_map.c:180
 sock_map_update_common+0x4f3/0x870 net/core/sock_map.c:506
 sock_map_update_elem_sys+0x3bb/0x570 net/core/sock_map.c:582
 bpf_map_update_value+0x36c/0x6c0 kernel/bpf/syscall.c:172
 map_update_elem+0x623/0x910 kernel/bpf/syscall.c:1641
 __sys_bpf+0xab9/0x4b40 kernel/bpf/syscall.c:5648
 __do_sys_bpf kernel/bpf/syscall.c:5767 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5765 [inline]
 __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:5765
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcf/0x260 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6bcc5b7729
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff751f0718 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fff751f08e8 RCX: 00007f6bcc5b7729
RDX: 0000000000000020 RSI: 0000000020000680 RDI: 0000000000000002
RBP: 00007f6bcc62a610 R08: 00007fff751f08e8 R09: 00007fff751f08e8
R10: 00007fff751f08e8 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fff751f08d8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>


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