syzbot


possible deadlock in sock_hash_update_common

Status: upstream: reported on 2024/04/28 11:53
Reported-by: syzbot+29d6dad94fbd484b33a9@syzkaller.appspotmail.com
First crash: 47d, last: 23d
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 possible deadlock in sock_hash_update_common origin:upstream C 1 23d 23d 0/3 upstream: reported C repro on 2024/05/22 22:02
upstream possible deadlock in sock_hash_update_common bpf net C error 38 9d15h 60d 0/27 upstream: reported C repro on 2024/04/15 17:04

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.1.91-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/17179 is trying to acquire lock:
ffff888047635290 (&psock->link_lock){+...}-{2:2}, at: spin_lock_bh include/linux/spinlock.h:356 [inline]
ffff888047635290 (&psock->link_lock){+...}-{2:2}, at: sock_map_add_link net/core/sock_map.c:136 [inline]
ffff888047635290 (&psock->link_lock){+...}-{2:2}, at: sock_hash_update_common+0x620/0xa30 net/core/sock_map.c:1022

but task is already holding lock:
ffff8880779028b0 (&htab->buckets[i].lock){+.-.}-{2:2}, at: sock_hash_update_common+0x20c/0xa30 net/core/sock_map.c:1006

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+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_hash_delete_elem+0x177/0x400 net/core/sock_map.c:938
       bpf_prog_b50d1fe9eb4be512+0x17/0x24
       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_map_free+0x1e3/0x3d0 net/core/sock_map.c:353
       process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
       worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
       kthread+0x28d/0x320 kernel/kthread.c:376
       ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

-> #0 (&psock->link_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
       spin_lock_bh include/linux/spinlock.h:356 [inline]
       sock_map_add_link net/core/sock_map.c:136 [inline]
       sock_hash_update_common+0x620/0xa30 net/core/sock_map.c:1022
       sock_map_update_elem_sys+0x5a0/0x910 net/core/sock_map.c:586
       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+0x3b/0xb0 arch/x86/entry/common.c:81
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

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-executor.4/17179:
 #0: ffff888045be9130 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1748 [inline]
 #0: ffff888045be9130 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_sk_acquire net/core/sock_map.c:119 [inline]
 #0: ffff888045be9130 (sk_lock-AF_UNIX){+.+.}-{0:0}, at: sock_map_update_elem_sys+0x1c8/0x910 net/core/sock_map.c:580
 #1: ffffffff8d12ac80 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #1: ffffffff8d12ac80 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #1: ffffffff8d12ac80 (rcu_read_lock){....}-{1:2}, at: sock_map_sk_acquire net/core/sock_map.c:120 [inline]
 #1: ffffffff8d12ac80 (rcu_read_lock){....}-{1:2}, at: sock_map_update_elem_sys+0x1d4/0x910 net/core/sock_map.c:580
 #2: ffff8880779028b0 (&htab->buckets[i].lock){+.-.}-{2:2}, at: sock_hash_update_common+0x20c/0xa30 net/core/sock_map.c:1006

stack backtrace:
CPU: 0 PID: 17179 Comm: syz-executor.4 Not tainted 6.1.91-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+0x1e3/0x2cb 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
 spin_lock_bh include/linux/spinlock.h:356 [inline]
 sock_map_add_link net/core/sock_map.c:136 [inline]
 sock_hash_update_common+0x620/0xa30 net/core/sock_map.c:1022
 sock_map_update_elem_sys+0x5a0/0x910 net/core/sock_map.c:586
 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+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff0b5e7cee9
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:00007ff0b6c160c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007ff0b5fabf80 RCX: 00007ff0b5e7cee9
RDX: 0000000000000020 RSI: 00000000200004c0 RDI: 0000000000000002
RBP: 00007ff0b5ec949e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007ff0b5fabf80 R15: 00007ffdc83dd738
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/22 18:53 linux-6.1.y 4078fa637fcd 4d098039 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf possible deadlock in sock_hash_update_common
2024/05/17 22:12 linux-6.1.y 4078fa637fcd a12e99e7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf possible deadlock in sock_hash_update_common
2024/04/28 11:52 linux-6.1.y f2295faba5e8 07b455f9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf possible deadlock in sock_hash_update_common
* Struck through repros no longer work on HEAD.