[v5.15] possible deadlock in sock_hash_update_common

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 83655231580b Linux 5.15.159
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13ef5748980000
kernel config: https://syzkaller.appspot.com/x/.config?x=ea870d7ee19c0a5c
dashboard link: https://syzkaller.appspot.com/bug?extid=f80304096a11734836df
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12b2fc8a980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1589b784980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7b95cc531586/disk-83655231.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/98b19a2ff947/vmlinux-83655231.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c9ebc1cdc369/bzImage-83655231.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f80304...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.159-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor154/3500 is trying to acquire lock:
ffff88814ad6d290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
ffff88814ad6d290 (&psock->link_lock){+...}-{2:2}, at: sock_map_add_link net/core/sock_map.c:136 [inline]
ffff88814ad6d290 (&psock->link_lock){+...}-{2:2}, at: sock_hash_update_common+0x620/0xa30 net/core/sock_map.c:1027

but task is already holding lock:
ffff88814ab8d520 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_update_common+0x20c/0xa30 net/core/sock_map.c:1011

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
bpf_prog_78b015942f8c5b4e+0x5b/0x714
bpf_dispatcher_nop_func include/linux/bpf.h:790 [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_run2+0x19e/0x340 kernel/trace/bpf_trace.c:1917
__bpf_trace_kfree+0x6e/0x90 include/trace/events/kmem.h:118
trace_kfree include/trace/events/kmem.h:118 [inline]
kfree+0x22f/0x270 mm/slub.c:4549
sk_psock_free_link include/linux/skmsg.h:421 [inline]
sock_map_del_link net/core/sock_map.c:160 [inline]
sock_map_unref+0x3ac/0x5d0 net/core/sock_map.c:182
sock_map_update_common+0x4ec/0x5b0 net/core/sock_map.c:508
sock_map_update_elem_sys+0x440/0x770 net/core/sock_map.c:588
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 (&psock->link_lock){+...}-{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_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:368 [inline]
sock_map_add_link net/core/sock_map.c:136 [inline]
sock_hash_update_common+0x620/0xa30 net/core/sock_map.c:1027
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

other info that might help us debug this:

Possible unsafe locking scenario:

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

*** DEADLOCK ***

3 locks held by syz-executor154/3500:
#0: ffff8880766e7920 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1668 [inline]
#0: ffff8880766e7920 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_sk_acquire net/core/sock_map.c:119 [inline]
#0: ffff8880766e7920 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_update_elem_sys+0x1c8/0x770 net/core/sock_map.c:584
#1: ffffffff8c91fae0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
#2: ffff88814ab8d520 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_update_common+0x20c/0xa30 net/core/sock_map.c:1011

stack backtrace:
CPU: 1 PID: 3500 Comm: syz-executor154 Not tainted 5.15.159-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
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_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:368 [inline]
sock_map_add_link net/core/sock_map.c:136 [inline]
sock_hash_update_common+0x620/0xa30 net/core/sock_map.c:1027
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
RIP: 0033:0x7faea3d200b9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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:00007fff946ed0e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007faea3d200b9
RDX: 0000000000000020 RSI: 0000000020000080 RDI: 0000000000000002
RBP: 0000000000000000 R08: 0000000000000006 R09: 0000000000000006
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001
</TASK>


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