KCSAN: data-race in expire_timers / try_to_del_timer_sync

10 views
Skip to first unread message

syzbot

unread,
Jun 29, 2020, 12:31:17 PM6/29/20
to syzkaller-upst...@googlegroups.com
Hello,

syzbot found the following crash on:

HEAD commit: 9ebcfadb Linux 5.8-rc3
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1438e39b100000
kernel config: https://syzkaller.appspot.com/x/.config?x=ef2c2e4f6006998c
dashboard link: https://syzkaller.appspot.com/bug?extid=abea4558531bae1ba9fe
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
CC: [ak...@linux-foundation.org b...@alien8.de hkall...@gmail.com h...@zytor.com linux-...@vger.kernel.org lu...@kernel.org mi...@redhat.com tg...@linutronix.de x...@kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+abea45...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in expire_timers / try_to_del_timer_sync

write to 0xffff88812c11cb08 of 8 bytes by interrupt on cpu 1:
expire_timers+0x11e/0x290 kernel/time/timer.c:1450
__run_timers+0x443/0x500 kernel/time/timer.c:1773
run_timer_softirq+0x2e/0x60 kernel/time/timer.c:1786
__do_softirq+0x198/0x360 kernel/softirq.c:292
asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
__run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
do_softirq_own_stack+0x5d/0x80 arch/x86/kernel/irq_64.c:77
invoke_softirq kernel/softirq.c:387 [inline]
__irq_exit_rcu+0x115/0x120 kernel/softirq.c:417
sysvec_apic_timer_interrupt+0xba/0xd0 arch/x86/kernel/apic/apic.c:1091
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:596
arch_local_irq_restore arch/x86/include/asm/paravirt.h:765 [inline]
kcsan_setup_watchpoint+0x47c/0x4d0 kernel/kcsan/core.c:542
common_file_perm security/apparmor/lsm.c:462 [inline]
apparmor_file_permission+0x30/0x270 security/apparmor/lsm.c:480
security_file_permission+0x42/0xa0 security/security.c:1431
rw_verify_area+0x12c/0x240 fs/read_write.c:400
do_splice_to fs/splice.c:862 [inline]
splice_direct_to_actor+0x23a/0x660 fs/splice.c:950
do_splice_direct+0xf2/0x170 fs/splice.c:1059
do_sendfile+0x562/0xb10 fs/read_write.c:1521
__do_sys_sendfile64 fs/read_write.c:1576 [inline]
__se_sys_sendfile64 fs/read_write.c:1568 [inline]
__x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1568
do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812c11cb08 of 8 bytes by task 10 on cpu 0:
try_to_del_timer_sync+0xd3/0x2d0 kernel/time/timer.c:1225
del_timer_sync kernel/time/timer.c:1365 [inline]
schedule_timeout+0x1bb/0x2c0 kernel/time/timer.c:1898
rcu_gp_fqs_loop kernel/rcu/tree.c:1874 [inline]
rcu_gp_kthread+0x9ad/0x1380 kernel/rcu/tree.c:2044
kthread+0x20d/0x230 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10 Comm: rcu_preempt Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
Reply all
Reply to author
Forward
0 new messages