[v5.15] possible deadlock in sock_map_delete_elem

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syzbot

unread,
Mar 21, 2024, 1:46:21 PMMar 21
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: b95c01af2113 Linux 5.15.152
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12844711180000
kernel config: https://syzkaller.appspot.com/x/.config?x=b26cb65e5b8ad5c7
dashboard link: https://syzkaller.appspot.com/bug?extid=9acd3e79e2d0385a2b8a
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/2fc98856fcae/disk-b95c01af.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3186db0dfe08/vmlinux-b95c01af.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0df136a3e808/bzImage-b95c01af.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9acd3e...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.15.152-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/5979 is trying to acquire lock:
ffff888059f151c0 (&stab->lock){+.-.}-{2:2}, at: __sock_map_delete net/core/sock_map.c:416 [inline]
ffff888059f151c0 (&stab->lock){+.-.}-{2:2}, at: sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448

but task is already holding lock:
ffff88805d3fc290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
ffff88805d3fc290 (&psock->link_lock){+...}-{2:2}, at: sock_map_del_link net/core/sock_map.c:147 [inline]
ffff88805d3fc290 (&psock->link_lock){+...}-{2:2}, at: sock_map_unref+0xcc/0x5d0 net/core/sock_map.c:182

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&psock->link_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
spin_lock_bh include/linux/spinlock.h:368 [inline]
sock_map_add_link net/core/sock_map.c:136 [inline]
sock_map_update_common+0x31c/0x5b0 net/core/sock_map.c:502
sock_map_update_elem_sys+0x440/0x770 net/core/sock_map.c:585
map_update_elem+0x6a0/0x7c0 kernel/bpf/syscall.c:1163
__sys_bpf+0x2fd/0x670 kernel/bpf/syscall.c:4617
__do_sys_bpf kernel/bpf/syscall.c:4733 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4731 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4731
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

-> #0 (&stab->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
__sock_map_delete net/core/sock_map.c:416 [inline]
sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448
bpf_prog_330576d32f01b34b+0x5b/0x6e0
bpf_dispatcher_nop_func include/linux/bpf.h:780 [inline]
__bpf_prog_run include/linux/filter.h:625 [inline]
bpf_prog_run include/linux/filter.h:632 [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:422 [inline]
sock_map_del_link net/core/sock_map.c:160 [inline]
sock_map_unref+0x3ac/0x5d0 net/core/sock_map.c:182
sock_hash_update_common+0x911/0xa30 net/core/sock_map.c:1028
sock_map_update_elem_sys+0x485/0x770 net/core/sock_map.c:587
map_update_elem+0x6a0/0x7c0 kernel/bpf/syscall.c:1163
__sys_bpf+0x2fd/0x670 kernel/bpf/syscall.c:4617
__do_sys_bpf kernel/bpf/syscall.c:4733 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4731 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4731
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&psock->link_lock);
lock(&stab->lock);
lock(&psock->link_lock);
lock(&stab->lock);

*** DEADLOCK ***

5 locks held by syz-executor.4/5979:
#0: ffff88807b1c6120 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1668 [inline]
#0: ffff88807b1c6120 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_sk_acquire net/core/sock_map.c:119 [inline]
#0: ffff88807b1c6120 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_update_elem_sys+0x1c8/0x770 net/core/sock_map.c:581
#1: ffffffff8c91f720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:268
#2: ffff88805afc9c20 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_update_common+0x20c/0xa30 net/core/sock_map.c:1005
#3: ffff88805d3fc290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
#3: ffff88805d3fc290 (&psock->link_lock){+...}-{2:2}, at: sock_map_del_link net/core/sock_map.c:147 [inline]
#3: ffff88805d3fc290 (&psock->link_lock){+...}-{2:2}, at: sock_map_unref+0xcc/0x5d0 net/core/sock_map.c:182
#4: ffffffff8c91f720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:268

stack backtrace:
CPU: 1 PID: 5979 Comm: syz-executor.4 Not tainted 5.15.152-syzkaller #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+0x1e3/0x2cb 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
__sock_map_delete net/core/sock_map.c:416 [inline]
sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448
bpf_prog_330576d32f01b34b+0x5b/0x6e0
bpf_dispatcher_nop_func include/linux/bpf.h:780 [inline]
__bpf_prog_run include/linux/filter.h:625 [inline]
bpf_prog_run include/linux/filter.h:632 [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:422 [inline]
sock_map_del_link net/core/sock_map.c:160 [inline]
sock_map_unref+0x3ac/0x5d0 net/core/sock_map.c:182
sock_hash_update_common+0x911/0xa30 net/core/sock_map.c:1028
sock_map_update_elem_sys+0x485/0x770 net/core/sock_map.c:587
map_update_elem+0x6a0/0x7c0 kernel/bpf/syscall.c:1163
__sys_bpf+0x2fd/0x670 kernel/bpf/syscall.c:4617
__do_sys_bpf kernel/bpf/syscall.c:4733 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4731 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:4731
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f9c0cd51da9
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:00007f9c0b2d20c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007f9c0ce7ff80 RCX: 00007f9c0cd51da9
RDX: 0000000000000020 RSI: 0000000020000040 RDI: 0000000000000002
RBP: 00007f9c0cd9e47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f9c0ce7ff80 R15: 00007ffd08342f38
</TASK>


---
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syzbot

unread,
Apr 4, 2024, 12:34:27 PMApr 4
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: 9465fef4ae35 Linux 5.15.153
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11469103180000
kernel config: https://syzkaller.appspot.com/x/.config?x=176c746ee3348b33
dashboard link: https://syzkaller.appspot.com/bug?extid=9acd3e79e2d0385a2b8a
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=140f449d180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1227929d180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2962c02652ce/disk-9465fef4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d0f5a1ce082d/vmlinux-9465fef4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/86b5b1eea636/bzImage-9465fef4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9acd3e...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
5.15.153-syzkaller #0 Not tainted
--------------------------------------------
kworker/1:0/21 is trying to acquire lock:
ffff88807c8339c0 (&stab->lock){+...}-{2:2}, at: __sock_map_delete net/core/sock_map.c:416 [inline]
ffff88807c8339c0 (&stab->lock){+...}-{2:2}, at: sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448

but task is already holding lock:
ffff88807c8339c0 (&stab->lock){+...}-{2:2}, at: __sock_map_delete net/core/sock_map.c:416 [inline]
ffff88807c8339c0 (&stab->lock){+...}-{2:2}, at: sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448

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

6 locks held by kworker/1:0/21:
#0: ffff888011c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283
#1: ffffc90000db7d20 ((work_completion)(&map->work)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2285
#2: ffffffff8c91f720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
#3: ffff88807c8339c0 (&stab->lock){+...}-{2:2}, at: __sock_map_delete net/core/sock_map.c:416 [inline]
#3: ffff88807c8339c0 (&stab->lock){+...}-{2:2}, at: sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448
#4: ffff888147d77290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:368 [inline]
#4: ffff888147d77290 (&psock->link_lock){+...}-{2:2}, at: sock_map_del_link net/core/sock_map.c:147 [inline]
#4: ffff888147d77290 (&psock->link_lock){+...}-{2:2}, at: sock_map_unref+0xcc/0x5d0 net/core/sock_map.c:182
#5: ffffffff8c91f720 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311

stack backtrace:
CPU: 1 PID: 21 Comm: kworker/1:0 Not tainted 5.15.153-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: events bpf_map_free_deferred
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
print_deadlock_bug kernel/locking/lockdep.c:2946 [inline]
check_deadlock kernel/locking/lockdep.c:2989 [inline]
validate_chain+0x46d2/0x5930 kernel/locking/lockdep.c:3775
__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
__sock_map_delete net/core/sock_map.c:416 [inline]
sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448
bpf_prog_2c29ac5cdc6b1842+0x3a/0xabc
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_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:422 [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_delete net/core/sock_map.c:422 [inline]
sock_map_delete_elem+0xc3/0x130 net/core/sock_map.c:448
bpf_prog_2c29ac5cdc6b1842+0x3a/0xabc
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_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
process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
</TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

syzbot

unread,
Apr 6, 2024, 12:22:19 PMApr 6
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 347385861c50 Linux 6.1.84
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16f01805180000
kernel config: https://syzkaller.appspot.com/x/.config?x=40dfd13b04bfc094
dashboard link: https://syzkaller.appspot.com/bug?extid=3a838a382d1ea3f3a4d7
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/584c64d6360b/disk-34738586.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ebe1b8334610/vmlinux-34738586.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e3d485b54a02/bzImage-34738586.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3a838a...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.1.84-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/3924 is trying to acquire lock:
ffff8880152a6a40 (&stab->lock){+.-.}-{2:2}, at: __sock_map_delete net/core/sock_map.c:416 [inline]
ffff8880152a6a40 (&stab->lock){+.-.}-{2:2}, at: sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448

but task is already holding lock:
ffff88805c343290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff88805c343290 (&psock->link_lock){+...}-{2:2}, at: sock_map_del_link net/core/sock_map.c:147 [inline]
ffff88805c343290 (&psock->link_lock){+...}-{2:2}, at: sock_map_unref+0xcc/0x5d0 net/core/sock_map.c:182

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&psock->link_lock){+...}-{2:2}:
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
spin_lock_bh include/linux/spinlock.h:356 [inline]
sock_map_add_link net/core/sock_map.c:136 [inline]
sock_map_update_common+0x31c/0x5b0 net/core/sock_map.c:502
sock_map_update_elem_sys+0x55b/0x910 net/core/sock_map.c:581
map_update_elem+0x503/0x680 kernel/bpf/syscall.c:1448
__sys_bpf+0x337/0x6c0 kernel/bpf/syscall.c:4993
__do_sys_bpf kernel/bpf/syscall.c:5109 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5107 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5107
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

-> #0 (&stab->lock){+.-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
__sock_map_delete net/core/sock_map.c:416 [inline]
sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448
bpf_prog_d284ea97e99fac5b+0x3f/0x43
bpf_dispatcher_nop_func include/linux/bpf.h:989 [inline]
__bpf_prog_run include/linux/filter.h:603 [inline]
bpf_prog_run include/linux/filter.h:610 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2273 [inline]
bpf_trace_run2+0x1fd/0x410 kernel/trace/bpf_trace.c:2312
__bpf_trace_kfree+0x6e/0x90 include/trace/events/kmem.h:94
trace_kfree include/trace/events/kmem.h:94 [inline]
kfree+0xf6/0x190 mm/slab_common.c:994
sk_psock_free_link include/linux/skmsg.h:416 [inline]
sock_map_del_link net/core/sock_map.c:160 [inline]
sock_map_unref+0x3ac/0x5d0 net/core/sock_map.c:182
sock_hash_update_common+0x911/0xa30 net/core/sock_map.c:1023
sock_map_update_elem_sys+0x5a0/0x910 net/core/sock_map.c:583
map_update_elem+0x503/0x680 kernel/bpf/syscall.c:1448
__sys_bpf+0x337/0x6c0 kernel/bpf/syscall.c:4993
__do_sys_bpf kernel/bpf/syscall.c:5109 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5107 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5107
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&psock->link_lock);
lock(&stab->lock);
lock(&psock->link_lock);
lock(&stab->lock);

*** DEADLOCK ***

5 locks held by syz-executor.4/3924:
#0: ffff8880584ac930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1745 [inline]
#0: ffff8880584ac930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_sk_acquire net/core/sock_map.c:119 [inline]
#0: ffff8880584ac930 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_update_elem_sys+0x1c8/0x910 net/core/sock_map.c:577
#1: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#1: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#1: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: sock_map_sk_acquire net/core/sock_map.c:120 [inline]
#1: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: sock_map_update_elem_sys+0x1d4/0x910 net/core/sock_map.c:577
#2: ffff888021135868 (&htab->buckets[i].lock){+...}-{2:2}, at: sock_hash_update_common+0x20c/0xa30 net/core/sock_map.c:1000
#3: ffff88805c343290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
#3: ffff88805c343290 (&psock->link_lock){+...}-{2:2}, at: sock_map_del_link net/core/sock_map.c:147 [inline]
#3: ffff88805c343290 (&psock->link_lock){+...}-{2:2}, at: sock_map_unref+0xcc/0x5d0 net/core/sock_map.c:182
#4: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#4: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#4: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2272 [inline]
#4: ffffffff8d12a980 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x110/0x410 kernel/trace/bpf_trace.c:2312

stack backtrace:
CPU: 1 PID: 3924 Comm: syz-executor.4 Not tainted 6.1.84-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+0x1e3/0x2cb lib/dump_stack.c:106
check_noncircular+0x2fa/0x3b0 kernel/locking/lockdep.c:2170
check_prev_add kernel/locking/lockdep.c:3090 [inline]
check_prevs_add kernel/locking/lockdep.c:3209 [inline]
validate_chain+0x1661/0x5950 kernel/locking/lockdep.c:3825
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
__sock_map_delete net/core/sock_map.c:416 [inline]
sock_map_delete_elem+0x97/0x130 net/core/sock_map.c:448
bpf_prog_d284ea97e99fac5b+0x3f/0x43
bpf_dispatcher_nop_func include/linux/bpf.h:989 [inline]
__bpf_prog_run include/linux/filter.h:603 [inline]
bpf_prog_run include/linux/filter.h:610 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2273 [inline]
bpf_trace_run2+0x1fd/0x410 kernel/trace/bpf_trace.c:2312
__bpf_trace_kfree+0x6e/0x90 include/trace/events/kmem.h:94
trace_kfree include/trace/events/kmem.h:94 [inline]
kfree+0xf6/0x190 mm/slab_common.c:994
sk_psock_free_link include/linux/skmsg.h:416 [inline]
sock_map_del_link net/core/sock_map.c:160 [inline]
sock_map_unref+0x3ac/0x5d0 net/core/sock_map.c:182
sock_hash_update_common+0x911/0xa30 net/core/sock_map.c:1023
sock_map_update_elem_sys+0x5a0/0x910 net/core/sock_map.c:583
map_update_elem+0x503/0x680 kernel/bpf/syscall.c:1448
__sys_bpf+0x337/0x6c0 kernel/bpf/syscall.c:4993
__do_sys_bpf kernel/bpf/syscall.c:5109 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5107 [inline]
__x64_sys_bpf+0x78/0x90 kernel/bpf/syscall.c:5107
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fda3627de69
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:00007fda370cc0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fda363abf80 RCX: 00007fda3627de69
RDX: 0000000000000020 RSI: 00000000200004c0 RDI: 0000000000000002
RBP: 00007fda362ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fda363abf80 R15: 00007ffedc83cc58

syzbot

unread,
Apr 10, 2024, 6:19:28 PMApr 10
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: bf1e3b1cb1e0 Linux 6.1.85
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13db765d180000
kernel config: https://syzkaller.appspot.com/x/.config?x=d3e21b90946dbbab
dashboard link: https://syzkaller.appspot.com/bug?extid=3a838a382d1ea3f3a4d7
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=12387261180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17308983180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/686a8153616f/disk-bf1e3b1c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1e494c0feb8c/vmlinux-bf1e3b1c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fa38d0bc0763/bzImage-bf1e3b1c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3a838a...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
6.1.85-syzkaller #0 Not tainted
--------------------------------------------
syz-executor373/3583 is trying to acquire lock:
ffff8880731af240 (&stab->lock){+...}-{2:2}, at: __sock_map_delete net/core/sock_map.c:419 [inline]
ffff8880731af240 (&stab->lock){+...}-{2:2}, at: sock_map_delete_elem+0x161/0x230 net/core/sock_map.c:451

but task is already holding lock:
ffff88807e68a240 (&stab->lock){+...}-{2:2}, at: __sock_map_delete net/core/sock_map.c:419 [inline]
ffff88807e68a240 (&stab->lock){+...}-{2:2}, at: sock_map_delete_elem+0x161/0x230 net/core/sock_map.c:451

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

4 locks held by syz-executor373/3583:
#0: ffff88807a8131b8 (&tsk->futex_exit_mutex){+.+.}-{3:3}, at: futex_cleanup_begin kernel/futex/core.c:1076 [inline]
#0: ffff88807a8131b8 (&tsk->futex_exit_mutex){+.+.}-{3:3}, at: futex_exit_release+0x30/0x1e0 kernel/futex/core.c:1128
#1: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#1: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#1: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2272 [inline]
#1: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x110/0x410 kernel/trace/bpf_trace.c:2312
#2: ffff88807e68a240 (&stab->lock){+...}-{2:2}, at: __sock_map_delete net/core/sock_map.c:419 [inline]
#2: ffff88807e68a240 (&stab->lock){+...}-{2:2}, at: sock_map_delete_elem+0x161/0x230 net/core/sock_map.c:451
#3: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#3: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#3: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: __bpf_trace_run kernel/trace/bpf_trace.c:2272 [inline]
#3: ffffffff8d12ac40 (rcu_read_lock){....}-{1:2}, at: bpf_trace_run2+0x110/0x410 kernel/trace/bpf_trace.c:2312

stack backtrace:
CPU: 0 PID: 3583 Comm: syz-executor373 Not tainted 6.1.85-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+0x1e3/0x2cb lib/dump_stack.c:106
print_deadlock_bug kernel/locking/lockdep.c:2983 [inline]
check_deadlock kernel/locking/lockdep.c:3026 [inline]
validate_chain+0x4711/0x5950 kernel/locking/lockdep.c:3812
__lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5049
lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:126 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:178
__sock_map_delete net/core/sock_map.c:419 [inline]
sock_map_delete_elem+0x161/0x230 net/core/sock_map.c:451
bpf_prog_2c29ac5cdc6b1842+0x3a/0x3e
bpf_dispatcher_nop_func include/linux/bpf.h:989 [inline]
__bpf_prog_run include/linux/filter.h:603 [inline]
bpf_prog_run include/linux/filter.h:610 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2273 [inline]
bpf_trace_run2+0x1fd/0x410 kernel/trace/bpf_trace.c:2312
__traceiter_contention_end+0x74/0xa0 include/trace/events/lock.h:122
trace_contention_end+0x14c/0x190 include/trace/events/lock.h:122
__pv_queued_spin_lock_slowpath+0x935/0xc50 kernel/locking/qspinlock.c:560
pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:591 [inline]
queued_spin_lock_slowpath+0x42/0x50 arch/x86/include/asm/qspinlock.h:51
queued_spin_lock include/asm-generic/qspinlock.h:114 [inline]
do_raw_spin_lock+0x269/0x370 kernel/locking/spinlock_debug.c:115
__sock_map_delete net/core/sock_map.c:419 [inline]
sock_map_delete_elem+0x161/0x230 net/core/sock_map.c:451
bpf_prog_2c29ac5cdc6b1842+0x3a/0x3e
bpf_dispatcher_nop_func include/linux/bpf.h:989 [inline]
__bpf_prog_run include/linux/filter.h:603 [inline]
bpf_prog_run include/linux/filter.h:610 [inline]
__bpf_trace_run kernel/trace/bpf_trace.c:2273 [inline]
bpf_trace_run2+0x1fd/0x410 kernel/trace/bpf_trace.c:2312
__traceiter_contention_end+0x74/0xa0 include/trace/events/lock.h:122
trace_contention_end+0x12f/0x170 include/trace/events/lock.h:122
__mutex_lock_common kernel/locking/mutex.c:612 [inline]
__mutex_lock+0x2ed/0xd80 kernel/locking/mutex.c:747
futex_cleanup_begin kernel/futex/core.c:1076 [inline]
futex_exit_release+0x30/0x1e0 kernel/futex/core.c:1128
exit_mm_release+0x16/0x30 kernel/fork.c:1505
exit_mm+0xa9/0x300 kernel/exit.c:535
do_exit+0x9f6/0x26a0 kernel/exit.c:856
do_group_exit+0x202/0x2b0 kernel/exit.c:1019
__do_sys_exit_group kernel/exit.c:1030 [inline]
__se_sys_exit_group kernel/exit.c:1028 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1028
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f09a6fab0f9
Code: 90 49 c7 c0 b8 ff ff ff be e7 00 00 00 ba 3c 00 00 00 eb 12 0f 1f 44 00 00 89 d0 0f 05 48 3d 00 f0 ff ff 77 1c f4 89 f0 0f 05 <48> 3d 00 f0 ff ff 76 e7 f7 d8 64 41 89 00 eb df 0f 1f 80 00 00 00
RSP: 002b:00007fffe9b993d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f09a6fab0f9
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 00007f09a70262b0 R08: ffffffffffffffb8 R09: 00000000000000a0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f09a70262b0
R13: 0000000000000000 R14: 00007f09a7026d20 R15: 00007f09a6f7c280
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