possible deadlock in rht_lock

Status: upstream: reported C repro on 2026/07/25 13:19
Subsystems: net fs
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+ef8d17bae14efb960935@syzkaller.appspotmail.com
First crash: 9d04h, last: 7h03m
Cause bisection: failed (error log, bisect log)
  
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ID Workflow Result Correct Bug Created Started Finished Revision Error
1ed00586 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ possible deadlock in rht_lock 2026/07/22 00:01 2026/07/22 00:01 2026/07/22 00:59 0d5a7c31

			
		
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [net?] [fs?] possible deadlock in rht_lock 0 (1) 2026/07/25 13:19

Sample crash report:
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz-executor/5768 is trying to acquire lock:
ffff88807d7f7038 (rhashtable_bucket){-.-.}-{0:0}, at: rht_lock+0x8b/0x180 include/linux/rhashtable.h:331

but task is already holding lock:
ffff88802cc48038 (rhashtable_bucket){-.-.}-{0:0}, at: rht_lock+0x8b/0x180 include/linux/rhashtable.h:331

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

       CPU0
       ----
  lock(rhashtable_bucket);
  lock(rhashtable_bucket);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

5 locks held by syz-executor/5768:
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: __rhashtable_insert_fast include/linux/rhashtable.h:774 [inline]
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rhashtable_insert_fast include/linux/rhashtable.h:887 [inline]
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: pidfs_add_pid+0x169/0xc50 fs/pidfs.c:178
 #1: ffff88802cc48038 (rhashtable_bucket){-.-.}-{0:0}, at: rht_lock+0x8b/0x180 include/linux/rhashtable.h:331
 #2: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #2: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #2: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: trace_call_bpf+0xb6/0xb80 kernel/trace/bpf_trace.c:-1
 #3: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #3: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #3: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: class_rcu_constructor include/linux/rcupdate.h:1183 [inline]
 #3: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rhtab_map_delete_elem+0x21/0x190 kernel/bpf/hashtab.c:2979
 #4: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #4: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #4: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: __rhashtable_remove_fast include/linux/rhashtable.h:1137 [inline]
 #4: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rhashtable_remove_fast include/linux/rhashtable.h:1175 [inline]
 #4: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rhtab_delete_elem+0x15c/0x1b30 kernel/bpf/hashtab.c:-1

stack backtrace:
CPU: 1 UID: 0 PID: 5768 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x24df/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 rht_lock+0xa3/0x180 include/linux/rhashtable.h:331
 __rhashtable_remove_fast_one include/linux/rhashtable.h:1065 [inline]
 __rhashtable_remove_fast include/linux/rhashtable.h:1146 [inline]
 rhashtable_remove_fast include/linux/rhashtable.h:1175 [inline]
 rhtab_delete_elem+0x404/0x1b30 kernel/bpf/hashtab.c:2954
 rhtab_map_delete_elem+0xe2/0x190 kernel/bpf/hashtab.c:2985
 bpf_prog_a4f1e23443ac9f8e+0x4e/0x56
 bpf_dispatcher_nop_func include/linux/bpf.h:1454 [inline]
 __bpf_prog_run include/linux/filter.h:724 [inline]
 bpf_prog_run include/linux/filter.h:731 [inline]
 bpf_prog_run_array include/linux/bpf.h:2597 [inline]
 trace_call_bpf+0x3f0/0xb80 kernel/trace/bpf_trace.c:147
 perf_trace_run_bpf_submit+0x78/0x170 kernel/events/core.c:11398
 do_perf_trace_lock include/trace/events/lock.h:49 [inline]
 perf_trace_lock+0x32d/0x410 include/trace/events/lock.h:49
 __do_trace_lock_release include/trace/events/lock.h:68 [inline]
 trace_lock_release include/trace/events/lock.h:68 [inline]
 lock_release+0x38e/0x3c0 kernel/locking/lockdep.c:5879
 rht_assign_unlock include/linux/rhashtable.h:431 [inline]
 __rhashtable_insert_fast include/linux/rhashtable.h:850 [inline]
 rhashtable_insert_fast include/linux/rhashtable.h:887 [inline]
 pidfs_add_pid+0x650/0xc50 fs/pidfs.c:178
 alloc_pid+0xe7a/0x1310 kernel/pid.c:338
 copy_process+0x20ea/0x4390 kernel/fork.c:2305
 kernel_clone+0x2d7/0x940 kernel/fork.c:2748
 __do_sys_clone kernel/fork.c:2889 [inline]
 __se_sys_clone kernel/fork.c:2873 [inline]
 __x64_sys_clone+0x1b6/0x230 kernel/fork.c:2873
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f703d7c6912
Code: 89 e7 e8 71 8b f7 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 66 89 c5 85 c0 75 3b 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffe5db74e40 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffe5db74e40 RCX: 00007f703d7c6912
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffe5db74fcc R08: 0000000000000000 R09: 0000000000000000
R10: 000055556f65e7d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 0000000000025e7d R15: 00007ffe5db75020
 </TASK>

Crashes (112):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/21 20:18 bpf 94515f3a7d42 7c5de9c3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/21 14:54 bpf 94515f3a7d42 7c5de9c3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/21 17:28 bpf-next 0bcca2a42cc5 7c5de9c3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/30 03:15 bpf 0ce37745d4bf cb1587ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/29 15:44 bpf 0ce37745d4bf cb1587ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/29 10:27 bpf 0ce37745d4bf 19622d9d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/28 21:36 bpf 0ce37745d4bf 19622d9d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/26 15:15 bpf 0ce37745d4bf 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/26 01:28 bpf 0ce37745d4bf 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/25 12:07 bpf 0ce37745d4bf 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/25 03:13 bpf 55c7bd2ddee5 05b26a28 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/24 22:09 bpf 55c7bd2ddee5 05b26a28 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/23 22:22 bpf 94515f3a7d42 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/23 21:15 bpf 94515f3a7d42 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/23 16:30 bpf 94515f3a7d42 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/23 12:55 bpf 94515f3a7d42 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/23 12:55 bpf 94515f3a7d42 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/23 12:54 bpf 94515f3a7d42 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/23 08:06 bpf 94515f3a7d42 881ce5c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-kasan-gce possible deadlock in rht_lock
2026/07/30 10:40 bpf-next fdec474c65fd 2377cd3d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/29 05:07 bpf-next fdec474c65fd 19622d9d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/28 14:46 bpf-next fcf741584a56 45ae1df4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/28 06:59 bpf-next fcf741584a56 45ae1df4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/27 15:20 bpf-next 4748a67f7111 4cb2b096 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/27 13:14 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/27 11:59 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/27 10:00 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/27 05:19 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/26 17:41 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/26 13:21 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/26 08:06 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/26 06:03 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/26 03:33 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/26 03:20 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/25 22:38 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/25 20:26 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/25 16:52 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/25 15:43 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/25 10:31 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/25 06:28 bpf-next 4748a67f7111 492bab15 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 20:00 bpf-next 87267b894598 05b26a28 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 17:10 bpf-next 87267b894598 05b26a28 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 13:56 bpf-next 87267b894598 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 13:35 bpf-next 87267b894598 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 11:48 bpf-next 87267b894598 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 10:44 bpf-next 87267b894598 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 08:11 bpf-next 87267b894598 544adce9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 02:15 bpf-next 87267b894598 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/24 00:08 bpf-next 87267b894598 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/23 12:12 bpf-next 87267b894598 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/23 11:06 bpf-next 87267b894598 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/23 10:41 bpf-next 87267b894598 71a13572 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
2026/07/23 09:31 bpf-next 87267b894598 881ce5c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-bpf-next-kasan-gce possible deadlock in rht_lock
* Struck through repros no longer work on HEAD.