Hello,
syzbot found the following issue on:
HEAD commit: 7a137e9bfa0e Linux 6.6.127
git tree: linux-6.6.y
console output:
https://syzkaller.appspot.com/x/log.txt?x=1054d0ba580000
kernel config:
https://syzkaller.appspot.com/x/.config?x=2a950bf7c0bff9f9
dashboard link:
https://syzkaller.appspot.com/bug?extid=783a26b2070ed282e2ca
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image:
https://storage.googleapis.com/syzbot-assets/04a02efb4a79/disk-7a137e9b.raw.xz
vmlinux:
https://storage.googleapis.com/syzbot-assets/f7b848f192f0/vmlinux-7a137e9b.xz
kernel image:
https://storage.googleapis.com/syzbot-assets/77a981f90b3d/bzImage-7a137e9b.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by:
syzbot+783a26...@syzkaller.appspotmail.com
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P6588/1:b..l P6566/1:b..l
rcu: (detected by 0, t=10502 jiffies, g=16809, q=410 ncpus=2)
task:syz.3.204 state:R running task stack:25320 pid:6566 ppid:5768 flags:0x00004006
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_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:692
RIP: 0010:lock_is_held_type+0x13e/0x190 kernel/locking/lockdep.c:5830
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc900031d7418 EFLAGS: 00000206
RAX: a5078a74b7525c00 RBX: ffff88801a7bbc00 RCX: a5078a74b7525c00
RDX: ffffc9000e5b0000 RSI: ffffffff8acada80 RDI: ffffffff8b1c82e0
RBP: 0000000000000000 R08: dffffc0000000000 R09: 1ffffffff2237ea0
R10: dffffc0000000000 R11: fffffbfff2237ea1 R12: 0000000000000002
R13: 0000000000000246 R14: ffffffff8d15ba78 R15: ffff88801a7bc730
lock_is_held include/linux/lockdep.h:288 [inline]
task_css include/linux/cgroup.h:436 [inline]
mem_cgroup_from_task+0x77/0x110 mm/memcontrol.c:1038
count_memcg_event_mm+0x195/0x3c0 include/linux/memcontrol.h:1101
mm_account_fault mm/memory.c:5222 [inline]
handle_mm_fault+0x2b25/0x4c00 mm/memory.c:5369
do_user_addr_fault+0x730/0x12c0 arch/x86/mm/fault.c:1371
handle_page_fault arch/x86/mm/fault.c:1463 [inline]
exc_page_fault+0x64/0x100 arch/x86/mm/fault.c:1516
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:608
RIP: 0010:__put_user_nocheck_4+0x7/0x10 arch/x86/lib/putuser.S:98
Code: 01 ca c3 f3 0f 1e fa 48 89 cb 48 c1 fb 3f 48 09 d9 0f 01 cb 89 01 31 c9 0f 01 ca c3 90 90 90 90 90 90 90 f3 0f 1e fa 0f 01 cb <89> 01 31 c9 0f 01 ca c3 90 f3 0f 1e fa 48 89 cb 48 c1 fb 3f 48 09
RSP: 0018:ffffc900031d78d8 EFLAGS: 00050202
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00002000001e1030
RDX: ffff88801a7bbc00 RSI: 0000000000000002 RDI: 00000000ffffffff
RBP: ffffc900031d7a70 R08: ffffc900031d76a7 R09: 1ffff9200063aed4
R10: dffffc0000000000 R11: fffff5200063aed5 R12: 0000000000000002
R13: 0000000000000000 R14: 000000000000783d R15: 00002000001e1000
____sys_recvmsg+0x3ba/0x5e0 net/socket.c:2826
___sys_recvmsg+0x216/0x590 net/socket.c:2855
do_recvmmsg+0x39a/0x870 net/socket.c:2949
__sys_recvmmsg net/socket.c:3028 [inline]
__do_sys_recvmmsg net/socket.c:3051 [inline]
__se_sys_recvmmsg net/socket.c:3044 [inline]
__x64_sys_recvmmsg+0x199/0x250 net/socket.c:3044
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: 0033:0x7f26d7b9c799
RSP: 002b:00007f26d8aa4028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f26d7e16090 RCX: 00007f26d7b9c799
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f26d7c32bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f26d7e16128 R14: 00007f26d7e16090 R15: 00007ffea91814f8
</TASK>
task:syz-executor state:R running task stack:28744 pid:6588 ppid:5766 flags:0x00004000
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:bpf_lsm_inode_permission+0x4/0x10 include/linux/lsm_hook_defs.h:137
Code: c0 c3 0f 1f 40 00 f3 0f 1e fa e8 77 c0 da ff 31 c0 c3 0f 1f 40 00 f3 0f 1e fa e8 67 c0 da ff 31 c0 c3 0f 1f 40 00 f3 0f 1e fa <e8> 57 c0 da ff 31 c0 c3 0f 1f 40 00 f3 0f 1e fa e8 47 c0 da ff 31
RSP: 0018:ffffc900032179c0 EFLAGS: 00000246
RAX: 1ffffffff194eb89 RBX: 0000000000000081 RCX: 0000000000000000
RDX: ffff888058a7bc00 RSI: 0000000000000081 RDI: ffff88807b92c4d8
RBP: 0000000000000000 R08: ffff888058a7bc00 R09: 0000000000000002
R10: 000000000000002f R11: 0000000000000000 R12: ffffffff8ca75c48
R13: dffffc0000000000 R14: ffff88807b92c4d8 R15: ffffffff8ca75c30
security_inode_permission+0xa0/0xf0 security/security.c:2111
may_lookup fs/namei.c:1728 [inline]
link_path_walk+0x286/0xe30 fs/namei.c:2279
path_parentat fs/namei.c:2538 [inline]
__filename_parentat+0x22a/0x650 fs/namei.c:2562
filename_parentat fs/namei.c:2580 [inline]
filename_create+0xd9/0x480 fs/namei.c:3871
do_symlinkat+0xc5/0x400 fs/namei.c:4500
__do_sys_symlinkat fs/namei.c:4523 [inline]
__se_sys_symlinkat fs/namei.c:4520 [inline]
__x64_sys_symlinkat+0x99/0xb0 fs/namei.c:4520
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: 0033:0x7fc9f4b9b857
RSP: 002b:00007ffdb9eb98f8 EFLAGS: 00000202 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc9f4b9b857
RDX: 00007fc9f4c33b9b RSI: 00000000ffffff9c RDI: 00007ffdb9eb9990
RBP: 00007ffdb9eb993c R08: 0000000000000001 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000002d
R13: 00000000000927c0 R14: 00000000000266d3 R15: 00007ffdb9eb9990
</TASK>
rcu: rcu_preempt kthread starved for 10237 jiffies! g16809 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:27656 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x1553/0x45a0 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
rcu_gp_kthread+0x9d/0x3b0 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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: c7 22 02 c3 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 83 d1 43 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2e 41 89 de 80
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c2
RAX: 8a2f927d2783df00 RBX: ffffffff8162a490 RCX: 8a2f927d2783df00
RDX: 0000000000000001 RSI: ffffffff8acac900 RDI: ffffffff8b1c82e0
RBP: ffffc90000187f20 R08: ffff8880b8f36b2b R09: 1ffff110171e6d65
R10: dffffc0000000000 R11: ffffed10171e6d66 R12: 1ffff1100384a780
R13: 1ffff92000030fc8 R14: 0000000000000001 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000006b000 CR3: 000000002f68e000 CR4: 00000000003526e0
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+0x1f0/0x4e0 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>
---
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