syzbot


INFO: rcu detected stall in sys_newfstat

Status: upstream: reported on 2025/06/24 03:58
Reported-by: syzbot+a1c47b55df2d49b27140@syzkaller.appspotmail.com
First crash: 33d, last: 33d
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sys_newfstat 1 2 25d 48d 0/3 upstream: reported on 2025/06/09 10:15
upstream INFO: rcu detected stall in sys_newfstat (2) mm 1 1 2027d 2027d 0/29 closed as invalid on 2020/01/08 05:33
upstream INFO: rcu detected stall in sys_newfstat mm 1 1 2062d 2062d 0/29 closed as invalid on 2019/12/04 14:04

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5139/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=9829, q=639 ncpus=2)
task:udevd           state:R  running task     stack:25160 pid:5139  ppid:1      flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 preempt_schedule_irq+0xb5/0x140 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:rcu_read_unlock include/linux/rcupdate.h:815 [inline]
RIP: 0010:prepend_path+0x716/0x960 fs/d_path.c:182
Code: 24 10 44 89 f6 83 e6 01 31 ff e8 05 19 8a ff 41 f6 c6 01 0f 85 f5 00 00 00 e8 c6 bc 6a 08 41 89 c6 31 ff 89 c6 e8 ea 18 8a ff <45> 85 f6 74 10 e8 c0 0f 74 ff 84 c0 74 0e e8 27 15 8a ff eb 58 e8
RSP: 0018:ffffc90003257978 EFLAGS: 00000293
RAX: ffffffff81fb8096 RBX: 0000000000000001 RCX: 0000000000000000
RDX: ffff88807d691e00 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90003257a48 R08: ffffffff8e49ab2f R09: 1ffffffff1c93565
R10: dffffc0000000000 R11: fffffbfff1c93566 R12: ffff88802ffcf080
R13: dffffc0000000000 R14: 0000000000000001 R15: 0000000000000000
 d_absolute_path+0xa2/0x140 fs/d_path.c:234
 tomoyo_get_absolute_path security/tomoyo/realpath.c:101 [inline]
 tomoyo_realpath_from_path+0x2d9/0x5d0 security/tomoyo/realpath.c:271
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x20f/0x4b0 security/tomoyo/file.c:822
 security_inode_getattr+0xd3/0x120 security/security.c:2153
 vfs_getattr fs/stat.c:173 [inline]
 vfs_fstat fs/stat.c:198 [inline]
 __do_sys_newfstat fs/stat.c:473 [inline]
 __se_sys_newfstat fs/stat.c:470 [inline]
 __x64_sys_newfstat+0x101/0x1f0 fs/stat.c:470
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0019b11ad7
RSP: 002b:00007fff55739c48 EFLAGS: 00000206 ORIG_RAX: 0000000000000005
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 00007f0019b11ad7
RDX: 0000000000090800 RSI: 00007fff55739c50 RDI: 000000000000000f
RBP: 00007fff55739c50 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000206 R12: 0000563291d99760
R13: 00000000000000fd R14: 000056328d6bcbe0 R15: 00007fff55739ff0
 </TASK>
rcu: rcu_preempt kthread starved for 10461 jiffies! g9829 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:R  running task     stack:27496 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x14e2/0x4580 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.6.94-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:148
Code: cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d 63 f0 41 00 f3 0f 1e fa fb f4 <c3> cc cc cc cc cc cc cc cc cc cc cc cc 66 0f 1f 00 55 41 57 41 56
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c2
RAX: e25f93921cd5c300 RBX: ffffffff81618a7b RCX: e25f93921cd5c300
RDX: 0000000000000001 RSI: ffffffff8aaab2c0 RDI: ffffffff8afc6900
RBP: ffffc90000187f20 R08: ffff8880b8f36d4b R09: 1ffff110171e6da9
R10: dffffc0000000000 R11: ffffed10171e6daa R12: ffffffff8e49ab28
R13: 0000000000000001 R14: 0000000000000001 R15: 1ffff1100364e780
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff55732ff8 CR3: 0000000063bab000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1eb/0x510 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/24 03:57 linux-6.6.y 6282921b6825 e2f27c35 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_newfstat
* Struck through repros no longer work on HEAD.