syzbot has found a reproducer for the following crash on:
HEAD commit: 18d0eae30e6a Merge tag 'char-misc-4.20-rc1' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14728be5400000
kernel config: https://syzkaller.appspot.com/x/.config?x=342f43de913c81b9
dashboard link: https://syzkaller.appspot.com/bug?extid=5b1df0420c523b45a953
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161d6999400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=110f4cf5400000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5b1df0420c523b45a953@xxxxxxxxxxxxxxxxxxxxxxxxx
=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
4.19.0+ #84 Not tainted
-----------------------------------------------------
syz-executor781/7254 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
00000000e70e96f7 (&ctx->fd_wqh){+.+.}, at: spin_lock
include/linux/spinlock.h:329 [inline]
00000000e70e96f7 (&ctx->fd_wqh){+.+.}, at: aio_poll+0x760/0x1420
fs/aio.c:1747
and this task is already holding:
000000009957d7d7 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq
include/linux/spinlock.h:354 [inline]
000000009957d7d7 (&(&ctx->ctx_lock)->rlock){..-.}, at:
aio_poll+0x738/0x1420 fs/aio.c:1746
which would create a new lock dependency:
(&(&ctx->ctx_lock)->rlock){..-.} -> (&ctx->fd_wqh){+.+.}
but this new dependency connects a SOFTIRQ-irq-safe lock:
(&(&ctx->ctx_lock)->rlock){..-.}
... which became SOFTIRQ-irq-safe at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
_raw_spin_lock_irq+0x61/0x80 kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0xbc/0x710 fs/aio.c:603
percpu_ref_put_many include/linux/percpu-refcount.h:285 [inline]
percpu_ref_put include/linux/percpu-refcount.h:301 [inline]
percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123 [inline]
percpu_ref_switch_to_atomic_rcu+0x563/0x730 lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:240 [inline]
rcu_do_batch kernel/rcu/tree.c:2437 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
rcu_process_callbacks+0x100a/0x1ac0 kernel/rcu/tree.c:2697
__do_softirq+0x308/0xb7e kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x17f/0x1c0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:801
native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57
arch_safe_halt arch/x86/include/asm/paravirt.h:151 [inline]
default_idle+0xbf/0x490 arch/x86/kernel/process.c:498
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489
default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x49b/0x5c0 kernel/sched/idle.c:262
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353
start_secondary+0x487/0x5f0 arch/x86/kernel/smpboot.c:271
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
to a SOFTIRQ-irq-unsafe lock:
(&ctx->fd_wqh){+.+.}
... which became SOFTIRQ-irq-unsafe at:
...
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read+0x2e4/0x2180 fs/userfaultfd.c:1029
userfaultfd_read+0x1e2/0x2c0 fs/userfaultfd.c:1191
__vfs_read+0x117/0x9b0 fs/read_write.c:416
vfs_read+0x17f/0x3c0 fs/read_write.c:452
ksys_read+0x101/0x260 fs/read_write.c:578
__do_sys_read fs/read_write.c:588 [inline]
__se_sys_read fs/read_write.c:586 [inline]
__x64_sys_read+0x73/0xb0 fs/read_write.c:586
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&ctx->fd_wqh);
local_irq_disable();
lock(&(&ctx->ctx_lock)->rlock);
lock(&ctx->fd_wqh);
<Interrupt>
lock(&(&ctx->ctx_lock)->rlock);
*** DEADLOCK ***
1 lock held by syz-executor781/7254:
#0: 000000009957d7d7 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq
include/linux/spinlock.h:354 [inline]
#0: 000000009957d7d7 (&(&ctx->ctx_lock)->rlock){..-.}, at:
aio_poll+0x738/0x1420 fs/aio.c:1746
the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
-> (&(&ctx->ctx_lock)->rlock){..-.} {
IN-SOFTIRQ-W at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock_irq
include/linux/spinlock_api_smp.h:128 [inline]
_raw_spin_lock_irq+0x61/0x80
kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0xbc/0x710 fs/aio.c:603
percpu_ref_put_many include/linux/percpu-refcount.h:285
[inline]
percpu_ref_put include/linux/percpu-refcount.h:301
[inline]
percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123
[inline]
percpu_ref_switch_to_atomic_rcu+0x563/0x730
lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:240 [inline]
rcu_do_batch kernel/rcu/tree.c:2437 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
rcu_process_callbacks+0x100a/0x1ac0
kernel/rcu/tree.c:2697
__do_softirq+0x308/0xb7e kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x17f/0x1c0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1cb/0x760
arch/x86/kernel/apic/apic.c:1061
apic_timer_interrupt+0xf/0x20
arch/x86/entry/entry_64.S:801
native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:57
arch_safe_halt arch/x86/include/asm/paravirt.h:151
[inline]
default_idle+0xbf/0x490 arch/x86/kernel/process.c:498
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489
default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x49b/0x5c0 kernel/sched/idle.c:262
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353
start_secondary+0x487/0x5f0
arch/x86/kernel/smpboot.c:271
secondary_startup_64+0xa4/0xb0
arch/x86/kernel/head_64.S:243
INITIAL USE at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128
[inline]
_raw_spin_lock_irq+0x61/0x80
kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0xbc/0x710 fs/aio.c:603
percpu_ref_put_many include/linux/percpu-refcount.h:285
[inline]
percpu_ref_put include/linux/percpu-refcount.h:301
[inline]
percpu_ref_call_confirm_rcu lib/percpu-refcount.c:123
[inline]
percpu_ref_switch_to_atomic_rcu+0x563/0x730
lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:240 [inline]
rcu_do_batch kernel/rcu/tree.c:2437 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
rcu_process_callbacks+0x100a/0x1ac0
kernel/rcu/tree.c:2697
__do_softirq+0x308/0xb7e kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x17f/0x1c0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x1cb/0x760
arch/x86/kernel/apic/apic.c:1061
apic_timer_interrupt+0xf/0x20
arch/x86/entry/entry_64.S:801
native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:57
arch_safe_halt arch/x86/include/asm/paravirt.h:151
[inline]
default_idle+0xbf/0x490 arch/x86/kernel/process.c:498
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:489
default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x49b/0x5c0 kernel/sched/idle.c:262
cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353
start_secondary+0x487/0x5f0 arch/x86/kernel/smpboot.c:271
secondary_startup_64+0xa4/0xb0
arch/x86/kernel/head_64.S:243
}
... key at: [<ffffffff8aed9b20>] __key.50623+0x0/0x40
... acquired at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
aio_poll+0x760/0x1420 fs/aio.c:1747
io_submit_one+0xa49/0xf80 fs/aio.c:1850
__do_sys_io_submit fs/aio.c:1916 [inline]
__se_sys_io_submit fs/aio.c:1887 [inline]
__x64_sys_io_submit+0x1b7/0x580 fs/aio.c:1887
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
the dependencies between the lock to be acquired
and SOFTIRQ-irq-unsafe lock:
-> (&ctx->fd_wqh){+.+.} {
HARDIRQ-ON-W at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock include/linux/spinlock_api_smp.h:142
[inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read+0x2e4/0x2180 fs/userfaultfd.c:1029
userfaultfd_read+0x1e2/0x2c0 fs/userfaultfd.c:1191
__vfs_read+0x117/0x9b0 fs/read_write.c:416
vfs_read+0x17f/0x3c0 fs/read_write.c:452
ksys_read+0x101/0x260 fs/read_write.c:578
__do_sys_read fs/read_write.c:588 [inline]
__se_sys_read fs/read_write.c:586 [inline]
__x64_sys_read+0x73/0xb0 fs/read_write.c:586
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
SOFTIRQ-ON-W at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock include/linux/spinlock_api_smp.h:142
[inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read+0x2e4/0x2180 fs/userfaultfd.c:1029
userfaultfd_read+0x1e2/0x2c0 fs/userfaultfd.c:1191
__vfs_read+0x117/0x9b0 fs/read_write.c:416
vfs_read+0x17f/0x3c0 fs/read_write.c:452
ksys_read+0x101/0x260 fs/read_write.c:578
__do_sys_read fs/read_write.c:588 [inline]
__se_sys_read fs/read_write.c:586 [inline]
__x64_sys_read+0x73/0xb0 fs/read_write.c:586
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
INITIAL USE at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock include/linux/spinlock_api_smp.h:142
[inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read+0x2e4/0x2180 fs/userfaultfd.c:1029
userfaultfd_read+0x1e2/0x2c0 fs/userfaultfd.c:1191
__vfs_read+0x117/0x9b0 fs/read_write.c:416
vfs_read+0x17f/0x3c0 fs/read_write.c:452
ksys_read+0x101/0x260 fs/read_write.c:578
__do_sys_read fs/read_write.c:588 [inline]
__se_sys_read fs/read_write.c:586 [inline]
__x64_sys_read+0x73/0xb0 fs/read_write.c:586
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
}
... key at: [<ffffffff8aed98a0>] __key.44253+0x0/0x40
... acquired at:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
aio_poll+0x760/0x1420 fs/aio.c:1747
io_submit_one+0xa49/0xf80 fs/aio.c:1850
__do_sys_io_submit fs/aio.c:1916 [inline]
__se_sys_io_submit fs/aio.c:1887 [inline]
__x64_sys_io_submit+0x1b7/0x580 fs/aio.c:1887
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
stack backtrace:
CPU: 0 PID: 7254 Comm: syz-executor781 Not tainted 4.19.0+ #84
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x244/0x39d lib/dump_stack.c:113
print_bad_irq_dependency kernel/locking/lockdep.c:1570 [inline]
check_usage.cold.58+0x6d5/0xad1 kernel/locking/lockdep.c:1602
check_irq_usage kernel/locking/lockdep.c:1658 [inline]
check_prev_add_irq kernel/locking/lockdep_states.h:8 [inline]
check_prev_add kernel/locking/lockdep.c:1868 [inline]
check_prevs_add kernel/locking/lockdep.c:1976 [inline]
validate_chain kernel/locking/lockdep.c:2347 [inline]
__lock_acquire+0x238a/0x4c20 kernel/locking/lockdep.c:3341
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
aio_poll+0x760/0x1420 fs/aio.c:1747
io_submit_one+0xa49/0xf80 fs/aio.c:1850
__do_sys_io_submit fs/aio.c:1916 [inline]
__se_sys_io_submit fs/aio.c:1887 [inline]
__x64_sys_io_submit+0x1b7/0x580 fs/aio.c:1887
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x447dc9
Code: e8 9c ba 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 5b 07 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fc840e69da8 EFLAGS: 00000293 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 00000000006e39e8 RCX: 0000000000447dc9
RDX: 0000000020000b00 RSI: 0000000000000001 RDI: 00007fc840e39000
RBP: 00000000006e39e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00000000006e39ec
R13: 702f74656e2f666c R14: 65732f636f72702f R15: 0000000000000000
