syzbot
BUG: unable to handle kernel paging request in percpu_ref_kill_and_confirm
Status:
upstream: reported on 2026/09/03 15:38
Reported-by: syzbot+903b461283452e7232f7@syzkaller.appspotmail.com
First crash: 1d18h, last: 1d00h
Sample crash report:
Unable to handle kernel paging request at virtual address dfff800000000001
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
[dfff800000000001] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 5342 Comm: syz.2.427 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 824000c5 (Nzcv daIF +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : percpu_ref_kill_and_confirm+0x118/0x150 lib/percpu-refcount.c:391
lr : percpu_ref_kill_and_confirm+0xec/0x150 lib/percpu-refcount.c:389
sp : ffff800020ec7770
x29: ffff800020ec7770 x28: 0000000000000008 x27: 1fffe00018887003
x26: ffff0000c4438018 x25: ffff0000c4438048 x24: 1fffe00018887008
x23: dfff800000000000 x22: 0000000000000008 x21: 0000000000000000
x20: 0000000000000000 x19: ffff0000c4438040 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082f2858 x15: 000000000004ffff
x14: ffff7000041d8ed4 x13: 1ffff000041d8ed4 x12: 0000000000080000
x11: 0000000000001288 x10: ffff800028d9a000 x9 : 1fffe00018887009
x8 : 0000000000000001 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000020 x4 : 0000000000000000 x3 : ffff8000082f2980
x2 : 0000000000000001 x1 : 0000000000000002 x0 : 0000000000000000
Call trace:
percpu_ref_kill_and_confirm+0x118/0x150 lib/percpu-refcount.c:391
percpu_ref_kill include/linux/percpu-refcount.h:149 [inline]
mddev_suspend+0x1c0/0x4e0 drivers/md/md.c:470
mddev_create_serial_pool+0x210/0x3fc drivers/md/md.c:221
backlog_store+0x2ac/0x3f0 drivers/md/md-bitmap.c:2508
md_attr_store+0x168/0x234 drivers/md/md.c:5626
sysfs_kf_write+0x1f8/0x274 fs/sysfs/file.c:140
kernfs_fop_write_iter+0x390/0x4b4 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2271 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x3c8/0x7c8 fs/read_write.c:584
ksys_write+0x12c/0x228 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__arm64_sys_write+0x7c/0x90 fs/read_write.c:646
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: 977f1b91 f9400328 91002116 d343fec8 (38776908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 977f1b91 bl 0xfffffffffdfc6e44
4: f9400328 ldr x8, [x25]
8: 91002116 add x22, x8, #0x8
c: d343fec8 lsr x8, x22, #3
* 10: 38776908 ldrb w8, [x8, x23] <-- trapping instruction
* Struck through repros no longer work on HEAD.