syzbot


INFO: rcu detected stall in dcache_dir_open

Status: upstream: reported on 2026/04/09 06:07
Reported-by: syzbot+73c5f39e178c7ad1bb1d@syzkaller.appspotmail.com
First crash: 74d, last: 43d
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in dcache_dir_open (2) mm 1 2 417d 425d 0/29 auto-obsoleted due to no activity on 2025/07/29 09:09
upstream INFO: rcu detected stall in dcache_dir_open mm 1 4 515d 596d 0/29 auto-obsoleted due to no activity on 2025/04/23 01:08

Sample crash report:
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5775/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=41085, q=147 ncpus=2)
task:syz-executor    state:R  running task     stack:21640 pid:5775  ppid:5768   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:check_kcov_mode kernel/kcov.c:193 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:245 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp8+0x36/0x80 kernel/kcov.c:320
Code: 70 8f 7c 7e 65 8b 15 71 8f 7c 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 57 83 b9 1c 16 00 00 00 74 4e 8b 91 f8 15 00 00 <83> fa 03 75 43 48 8b 91 00 16 00 00 44 8b 89 fc 15 00 00 49 c1 e1
RSP: 0018:ffffc9000457f5a0 EFLAGS: 00000246
RAX: ffffffff81ea4041 RBX: 0000000000000005 RCX: ffff888021ce5a00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: dffffc0000000000 R08: ffff88801953d7a7 R09: 1ffff110032a7af4
R10: dffffc0000000000 R11: ffffed10032a7af5 R12: 0000000000000000
R13: 1ffffffff2e66f30 R14: ffff88801953d7a8 R15: 0000000000000003
 __page_table_check_zero+0x191/0x4b0 mm/page_table_check.c:153
 page_table_check_free include/linux/page_table_check.h:41 [inline]
 free_pages_prepare mm/page_alloc.c:1182 [inline]
 free_unref_page_prepare+0x7c1/0x8c0 mm/page_alloc.c:2365
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2458
 __slab_free+0x35a/0x400 mm/slub.c:3736
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc_lru+0x111/0x2d0 mm/slub.c:3526
 __d_alloc+0x31/0x730 fs/dcache.c:1773
 d_alloc_anon fs/dcache.c:1874 [inline]
 d_alloc_cursor+0x44/0xd0 fs/dcache.c:1880
 dcache_dir_open+0x41/0x80 fs/libfs.c:83
 do_dentry_open+0x8c6/0x1500 fs/open.c:929
 do_open fs/namei.c:3640 [inline]
 path_openat+0x27f1/0x3230 fs/namei.c:3797
 do_filp_open+0x1f5/0x430 fs/namei.c:3824
 do_sys_openat2+0x134/0x1d0 fs/open.c:1421
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f89e259c0fc
RSP: 002b:00007ffcb2e165c0 EFLAGS: 00000206 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00000000000003e1 RCX: 00007f89e259c0fc
RDX: 0000000000090800 RSI: 00007f89e26326ab RDI: 00000000ffffff9c
RBP: 00007ffcb2e1666c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 000000000000015c
R13: 0000000000000000 R14: 0000000000056808 R15: 00007ffcb2e166c0
 </TASK>
net_ratelimit: 14170 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
net_ratelimit: 15334 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:5a:7e:95:f8:df:da, vlan:0)

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/09 15:05 linux-6.6.y 3b9f64db0496 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in dcache_dir_open
2026/04/09 06:06 linux-6.6.y 80de0a958133 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in dcache_dir_open
* Struck through repros no longer work on HEAD.