[v5.15] possible deadlock in sk_psock_drop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c52b9710c83d Linux 5.15.156
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=117d025f180000
kernel config: https://syzkaller.appspot.com/x/.config?x=567b6ddc38438433
dashboard link: https://syzkaller.appspot.com/bug?extid=550b35ccfab56dec85c5
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/0f3c5c4c6b95/disk-c52b9710.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/147d1652ac2d/vmlinux-c52b9710.xz
kernel image: https://storage.googleapis.com/syzbot-assets/65adb2c52de8/bzImage-c52b9710.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+550b35...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.156-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/6694 is trying to acquire lock:
ffff888079ea0bd8 (clock-AF_UNIX){+...}-{2:2}, at: sk_psock_drop+0x2f/0x3b0 net/core/skmsg.c:835

but task is already holding lock:
ffff8880749e1e20 (&htab->buckets[i].lock){+.-.}-{2:2}, at: sock_hash_delete_elem+0x177/0x400 net/core/sock_map.c:943

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+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
sock_hash_delete_elem+0x177/0x400 net/core/sock_map.c:943
0xffffffffa00365ba
bpf_dispatcher_nop_func include/linux/bpf.h:785 [inline]
__bpf_prog_run include/linux/filter.h:628 [inline]
bpf_prog_run include/linux/filter.h:635 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:1880 [inline]
bpf_trace_run4+0x1ea/0x390 kernel/trace/bpf_trace.c:1919
__bpf_trace_mm_page_alloc+0xba/0xe0 include/trace/events/kmem.h:201
__traceiter_mm_page_alloc+0x35/0x50 include/trace/events/kmem.h:201
trace_mm_page_alloc include/trace/events/kmem.h:201 [inline]
__alloc_pages+0x6e0/0x700 mm/page_alloc.c:5445
alloc_slab_page mm/slub.c:1775 [inline]
allocate_slab mm/slub.c:1912 [inline]
new_slab+0xbb/0x4b0 mm/slub.c:1975
___slab_alloc+0x6f6/0xe10 mm/slub.c:3008
__slab_alloc mm/slub.c:3095 [inline]
slab_alloc_node mm/slub.c:3186 [inline]
kmem_cache_alloc_node_trace+0x1ce/0x2e0 mm/slub.c:3270
kmalloc_node include/linux/slab.h:609 [inline]
kzalloc_node include/linux/slab.h:732 [inline]
sk_psock_init+0x114/0x6b0 net/core/skmsg.c:712
sock_map_link+0x708/0xdb0 net/core/sock_map.c:277
sock_hash_update_common+0xd1/0xa30 net/core/sock_map.c:1001
sock_map_update_elem_sys+0x485/0x770 net/core/sock_map.c:590
map_update_elem+0x6a0/0x7c0 kernel/bpf/syscall.c:1185
__sys_bpf+0x2fd/0x670 kernel/bpf/syscall.c:4639
__do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (clock-AF_UNIX){+...}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_write_lock_bh include/linux/rwlock_api_smp.h:203 [inline]
_raw_write_lock_bh+0x31/0x40 kernel/locking/spinlock.c:324
sk_psock_drop+0x2f/0x3b0 net/core/skmsg.c:835
sock_hash_delete_elem+0x388/0x400 net/core/sock_map.c:947
map_delete_elem+0x431/0x580 kernel/bpf/syscall.c:1239
__sys_bpf+0x311/0x670 kernel/bpf/syscall.c:4642
__do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&htab->buckets[i].lock);
lock(clock-AF_UNIX);
lock(&htab->buckets[i].lock);
lock(clock-AF_UNIX);

*** DEADLOCK ***

2 locks held by syz-executor.2/6694:
#0: ffffffff8c91fb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
#1: ffff8880749e1e20 (&htab->buckets[i].lock){+.-.}-{2:2}, at: sock_hash_delete_elem+0x177/0x400 net/core/sock_map.c:943

stack backtrace:
CPU: 0 PID: 6694 Comm: syz-executor.2 Not tainted 5.15.156-syzkaller #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+0x1e3/0x2d0 lib/dump_stack.c:106
check_noncircular+0x2f8/0x3b0 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
__raw_write_lock_bh include/linux/rwlock_api_smp.h:203 [inline]
_raw_write_lock_bh+0x31/0x40 kernel/locking/spinlock.c:324
sk_psock_drop+0x2f/0x3b0 net/core/skmsg.c:835
sock_hash_delete_elem+0x388/0x400 net/core/sock_map.c:947
map_delete_elem+0x431/0x580 kernel/bpf/syscall.c:1239
__sys_bpf+0x311/0x670 kernel/bpf/syscall.c:4642
__do_sys_bpf kernel/bpf/syscall.c:4755 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4753 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4753
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f7e4e4b7ea9
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:00007f7e4ca2a0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f7e4e5e5f80 RCX: 00007f7e4e4b7ea9
RDX: 0000000000000020 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00007f7e4e5044a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f7e4e5e5f80 R15: 00007fffe9eb8388
</TASK>


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