* possible deadlock in io_submit_one
@ 2019-02-05 2:03 syzbot
2019-03-11 13:23 ` syzbot
2019-06-12 19:48 ` Eric Biggers
0 siblings, 2 replies; 4+ messages in thread
From: syzbot @ 2019-02-05 2:03 UTC (permalink / raw)
To: bcrl, linux-aio, linux-fsdevel, linux-kernel, syzkaller-bugs, viro
Hello,
syzbot found the following crash on:
HEAD commit: 5eeb63359b1e Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17906f64c00000
kernel config: https://syzkaller.appspot.com/x/.config?x=2e0064f906afee10
dashboard link: https://syzkaller.appspot.com/bug?extid=a3accb352f9c22041cfa
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=156479f8c00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=128c75c4c00000
IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+a3accb352f9c22041cfa@syzkaller.appspotmail.com
=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
5.0.0-rc4+ #56 Not tainted
-----------------------------------------------------
syz-executor263/8874 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
00000000c469f622 (&ctx->fd_wqh){....}, at: spin_lock
include/linux/spinlock.h:329 [inline]
00000000c469f622 (&ctx->fd_wqh){....}, at: aio_poll fs/aio.c:1772 [inline]
00000000c469f622 (&ctx->fd_wqh){....}, at: __io_submit_one fs/aio.c:1875
[inline]
00000000c469f622 (&ctx->fd_wqh){....}, at: io_submit_one+0xedf/0x1cf0
fs/aio.c:1908
and this task is already holding:
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq
include/linux/spinlock.h:354 [inline]
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll
fs/aio.c:1771 [inline]
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one
fs/aio.c:1875 [inline]
00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at:
io_submit_one+0xeb6/0x1cf0 fs/aio.c:1908
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+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline]
_raw_spin_lock_irq+0x60/0x80 kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0x2d/0x4a0 fs/aio.c:610
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+0x3e7/0x520 lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:240 [inline]
rcu_do_batch kernel/rcu/tree.c:2452 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2773 [inline]
rcu_process_callbacks+0x928/0x1390 kernel/rcu/tree.c:2754
__do_softirq+0x266/0x95a kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:57
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
default_idle_call+0x36/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x386/0x570 kernel/sched/idle.c:262
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
rest_init+0x245/0x37b init/main.c:442
arch_call_rest_init+0xe/0x1b
start_kernel+0x808/0x841 init/main.c:740
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
to a SOFTIRQ-irq-unsafe lock:
(&ctx->fault_pending_wqh){+.+.}
... which became SOFTIRQ-irq-unsafe at:
...
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_release+0x497/0x6d0 fs/userfaultfd.c:916
__fput+0x2df/0x8d0 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x14a/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x273/0x2c0 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Chain exists of:
&(&ctx->ctx_lock)->rlock --> &ctx->fd_wqh --> &ctx->fault_pending_wqh
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&ctx->fault_pending_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-executor263/8874:
#0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq
include/linux/spinlock.h:354 [inline]
#0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll
fs/aio.c:1771 [inline]
#0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one
fs/aio.c:1875 [inline]
#0: 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at:
io_submit_one+0xeb6/0x1cf0 fs/aio.c:1908
the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
-> (&(&ctx->ctx_lock)->rlock){..-.} {
IN-SOFTIRQ-W at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock_irq
include/linux/spinlock_api_smp.h:128 [inline]
_raw_spin_lock_irq+0x60/0x80
kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0x2d/0x4a0 fs/aio.c:610
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+0x3e7/0x520
lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:240 [inline]
rcu_do_batch kernel/rcu/tree.c:2452 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2773 [inline]
rcu_process_callbacks+0x928/0x1390
kernel/rcu/tree.c:2754
__do_softirq+0x266/0x95a kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x14a/0x570
arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20
arch/x86/entry/entry_64.S:807
native_safe_halt+0x2/0x10
arch/x86/include/asm/irqflags.h:57
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
default_idle_call+0x36/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x386/0x570 kernel/sched/idle.c:262
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
rest_init+0x245/0x37b init/main.c:442
arch_call_rest_init+0xe/0x1b
start_kernel+0x808/0x841 init/main.c:740
x86_64_start_reservations+0x29/0x2b
arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x77/0x7b
arch/x86/kernel/head64.c:451
secondary_startup_64+0xa4/0xb0
arch/x86/kernel/head_64.S:243
INITIAL USE at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128
[inline]
_raw_spin_lock_irq+0x60/0x80
kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
free_ioctx_users+0x2d/0x4a0 fs/aio.c:610
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+0x3e7/0x520
lib/percpu-refcount.c:158
__rcu_reclaim kernel/rcu/rcu.h:240 [inline]
rcu_do_batch kernel/rcu/tree.c:2452 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2773 [inline]
rcu_process_callbacks+0x928/0x1390 kernel/rcu/tree.c:2754
__do_softirq+0x266/0x95a kernel/softirq.c:292
invoke_softirq kernel/softirq.c:373 [inline]
irq_exit+0x180/0x1d0 kernel/softirq.c:413
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x14a/0x570
arch/x86/kernel/apic/apic.c:1062
apic_timer_interrupt+0xf/0x20
arch/x86/entry/entry_64.S:807
native_safe_halt+0x2/0x10
arch/x86/include/asm/irqflags.h:57
arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555
default_idle_call+0x36/0x90 kernel/sched/idle.c:93
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x386/0x570 kernel/sched/idle.c:262
cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353
start_secondary+0x404/0x5c0 arch/x86/kernel/smpboot.c:271
secondary_startup_64+0xa4/0xb0
arch/x86/kernel/head_64.S:243
}
... key at: [<ffffffff8a5760a0>] __key.51972+0x0/0x40
... acquired at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
aio_poll fs/aio.c:1772 [inline]
__io_submit_one fs/aio.c:1875 [inline]
io_submit_one+0xedf/0x1cf0 fs/aio.c:1908
__do_sys_io_submit fs/aio.c:1953 [inline]
__se_sys_io_submit fs/aio.c:1923 [inline]
__x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923
do_syscall_64+0x103/0x610 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->fault_pending_wqh){+.+.} {
HARDIRQ-ON-W at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock include/linux/spinlock_api_smp.h:142
[inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_release+0x497/0x6d0 fs/userfaultfd.c:916
__fput+0x2df/0x8d0 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x14a/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188
[inline]
exit_to_usermode_loop+0x273/0x2c0
arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197
[inline]
syscall_return_slowpath arch/x86/entry/common.c:268
[inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
SOFTIRQ-ON-W at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock include/linux/spinlock_api_smp.h:142
[inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_release+0x497/0x6d0 fs/userfaultfd.c:916
__fput+0x2df/0x8d0 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x14a/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188
[inline]
exit_to_usermode_loop+0x273/0x2c0
arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197
[inline]
syscall_return_slowpath arch/x86/entry/common.c:268
[inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
INITIAL USE at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock include/linux/spinlock_api_smp.h:142
[inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198
__vfs_read+0x116/0x8c0 fs/read_write.c:416
vfs_read+0x194/0x3e0 fs/read_write.c:452
ksys_read+0xea/0x1f0 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+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
}
... key at: [<ffffffff8a575ee0>] __key.44851+0x0/0x40
... acquired at:
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
userfaultfd_ctx_read fs/userfaultfd.c:1040 [inline]
userfaultfd_read+0x540/0x1940 fs/userfaultfd.c:1198
__vfs_read+0x116/0x8c0 fs/read_write.c:416
vfs_read+0x194/0x3e0 fs/read_write.c:452
ksys_read+0xea/0x1f0 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+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> (&ctx->fd_wqh){....} {
INITIAL USE at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:128
[inline]
_raw_spin_lock_irq+0x60/0x80
kernel/locking/spinlock.c:160
spin_lock_irq include/linux/spinlock.h:354 [inline]
userfaultfd_ctx_read fs/userfaultfd.c:1036 [inline]
userfaultfd_read+0x27a/0x1940 fs/userfaultfd.c:1198
__vfs_read+0x116/0x8c0 fs/read_write.c:416
vfs_read+0x194/0x3e0 fs/read_write.c:452
ksys_read+0xea/0x1f0 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+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
}
... key at: [<ffffffff8a575e20>] __key.44854+0x0/0x40
... acquired at:
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
aio_poll fs/aio.c:1772 [inline]
__io_submit_one fs/aio.c:1875 [inline]
io_submit_one+0xedf/0x1cf0 fs/aio.c:1908
__do_sys_io_submit fs/aio.c:1953 [inline]
__se_sys_io_submit fs/aio.c:1923 [inline]
__x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
stack backtrace:
CPU: 1 PID: 8874 Comm: syz-executor263 Not tainted 5.0.0-rc4+ #56
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+0x172/0x1f0 lib/dump_stack.c:113
print_bad_irq_dependency kernel/locking/lockdep.c:1573 [inline]
check_usage.cold+0x60f/0x940 kernel/locking/lockdep.c:1605
check_irq_usage kernel/locking/lockdep.c:1661 [inline]
check_prev_add_irq kernel/locking/lockdep_states.h:8 [inline]
check_prev_add kernel/locking/lockdep.c:1871 [inline]
check_prevs_add kernel/locking/lockdep.c:1979 [inline]
validate_chain kernel/locking/lockdep.c:2350 [inline]
__lock_acquire+0x1f47/0x4700 kernel/locking/lockdep.c:3338
lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:3841
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
spin_lock include/linux/spinlock.h:329 [inline]
aio_poll fs/aio.c:1772 [inline]
__io_submit_one fs/aio.c:1875 [inline]
io_submit_one+0xedf/0x1cf0 fs/aio.c:1908
__do_sys_io_submit fs/aio.c:1953 [inline]
__se_sys_io_submit fs/aio.c:1923 [inline]
__x64_sys_io_submit+0x1bd/0x580 fs/aio.c:1923
---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this bug report. See:
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syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: possible deadlock in io_submit_one 2019-02-05 2:03 possible deadlock in io_submit_one syzbot @ 2019-03-11 13:23 ` syzbot 2019-06-12 19:48 ` Eric Biggers 1 sibling, 0 replies; 4+ messages in thread From: syzbot @ 2019-03-11 13:23 UTC (permalink / raw) To: adam.manzanares, avi, bcrl, darrick.wong, gregkh, hch, jmoyer, linux-aio, linux-fsdevel, linux-kernel, syzkaller-bugs, viro syzbot has bisected this bug to: commit bfe4037e722ec672c9dafd5730d9132afeeb76e9 Author: Christoph Hellwig <hch@lst.de> Date: Mon Jul 16 07:08:20 2018 +0000 aio: implement IOCB_CMD_POLL bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=108886bd200000 start commit: bfe4037e aio: implement IOCB_CMD_POLL git tree: upstream final crash: https://syzkaller.appspot.com/x/report.txt?x=128886bd200000 console output: https://syzkaller.appspot.com/x/log.txt?x=148886bd200000 kernel config: https://syzkaller.appspot.com/x/.config?x=2e0064f906afee10 dashboard link: https://syzkaller.appspot.com/bug?extid=a3accb352f9c22041cfa userspace arch: amd64 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=156479f8c00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=128c75c4c00000 Reported-by: syzbot+a3accb352f9c22041cfa@syzkaller.appspotmail.com Fixes: bfe4037e ("aio: implement IOCB_CMD_POLL") ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: possible deadlock in io_submit_one 2019-02-05 2:03 possible deadlock in io_submit_one syzbot 2019-03-11 13:23 ` syzbot @ 2019-06-12 19:48 ` Eric Biggers 2019-06-27 7:50 ` [PATCH] userfaultfd: disable irqs for fault_pending and event locks Eric Biggers 1 sibling, 1 reply; 4+ messages in thread From: Eric Biggers @ 2019-06-12 19:48 UTC (permalink / raw) To: Bart Van Assche, Christoph Hellwig Cc: syzbot, bcrl, linux-aio, linux-fsdevel, linux-kernel, syzkaller-bugs, viro Hi Bart and Christoph, On Mon, Feb 04, 2019 at 06:03:04PM -0800, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 5eeb63359b1e Merge tag 'for-linus' of git://git.kernel.org.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=17906f64c00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=2e0064f906afee10 > dashboard link: https://syzkaller.appspot.com/bug?extid=a3accb352f9c22041cfa > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=156479f8c00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=128c75c4c00000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+a3accb352f9c22041cfa@syzkaller.appspotmail.com > > ===================================================== > WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected > 5.0.0-rc4+ #56 Not tainted > ----------------------------------------------------- > syz-executor263/8874 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: > 00000000c469f622 (&ctx->fd_wqh){....}, at: spin_lock > include/linux/spinlock.h:329 [inline] > 00000000c469f622 (&ctx->fd_wqh){....}, at: aio_poll fs/aio.c:1772 [inline] > 00000000c469f622 (&ctx->fd_wqh){....}, at: __io_submit_one fs/aio.c:1875 > [inline] > 00000000c469f622 (&ctx->fd_wqh){....}, at: io_submit_one+0xedf/0x1cf0 > fs/aio.c:1908 > > and this task is already holding: > 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq > include/linux/spinlock.h:354 [inline] > 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll > fs/aio.c:1771 [inline] > 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one > fs/aio.c:1875 [inline] > 00000000829de875 (&(&ctx->ctx_lock)->rlock){..-.}, at: > io_submit_one+0xeb6/0x1cf0 fs/aio.c:1908 > which would create a new lock dependency: > (&(&ctx->ctx_lock)->rlock){..-.} -> (&ctx->fd_wqh){....} > This is still happening. See https://syzkaller.appspot.com/text?tag=CrashReport&x=129eb971a00000 for a report on Linus' tree from 5 days ago. I see that a few months ago there was a commit commit d3d6a18d7d351cbcc9b33dbedf710e65f8ce1595 Author: Bart Van Assche <bvanassche@acm.org> Date: Fri Feb 8 16:59:49 2019 -0800 aio: Fix locking in aio_poll() but apparently it didn't fully fix the problem. - Eric ^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] userfaultfd: disable irqs for fault_pending and event locks 2019-06-12 19:48 ` Eric Biggers @ 2019-06-27 7:50 ` Eric Biggers 0 siblings, 0 replies; 4+ messages in thread From: Eric Biggers @ 2019-06-27 7:50 UTC (permalink / raw) To: linux-mm, Andrew Morton Cc: linux-aio, linux-fsdevel, syzkaller-bugs, Christoph Hellwig, Andrea Arcangeli From: Eric Biggers <ebiggers@google.com> When IOCB_CMD_POLL is used on a userfaultfd, aio_poll() disables IRQs and takes kioctx::ctx_lock, then userfaultfd_ctx::fd_wqh.lock. This may have to wait for userfaultfd_ctx::fd_wqh.lock to be released by userfaultfd_ctx_read(), which can be waiting for userfaultfd_ctx::fault_pending_wqh.lock or userfaultfd_ctx::event_wqh.lock. But elsewhere the fault_pending_wqh and event_wqh locks are taken with IRQs enabled. Since the IRQ handler may take kioctx::ctx_lock, lockdep reports that a deadlock is possible. Fix it by always disabling IRQs when taking the fault_pending_wqh and event_wqh locks. Commit ae62c16e105a ("userfaultfd: disable irqs when taking the waitqueue lock") didn't fix this because it only accounted for the fd_wqh lock, not the other locks nested inside it. Reported-by: syzbot+fab6de82892b6b9c6191@syzkaller.appspotmail.com Reported-by: syzbot+53c0b767f7ca0dc0c451@syzkaller.appspotmail.com Reported-by: syzbot+a3accb352f9c22041cfa@syzkaller.appspotmail.com Fixes: bfe4037e722e ("aio: implement IOCB_CMD_POLL") Cc: <stable@vger.kernel.org> # v4.19+ Signed-off-by: Eric Biggers <ebiggers@google.com> --- fs/userfaultfd.c | 42 ++++++++++++++++++++++++++---------------- 1 file changed, 26 insertions(+), 16 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index ae0b8b5f69e6..ccbdbd62f0d8 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -40,6 +40,16 @@ enum userfaultfd_state { /* * Start with fault_pending_wqh and fault_wqh so they're more likely * to be in the same cacheline. + * + * Locking order: + * fd_wqh.lock + * fault_pending_wqh.lock + * fault_wqh.lock + * event_wqh.lock + * + * To avoid deadlocks, IRQs must be disabled when taking any of the above locks, + * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's + * also taken in IRQ context. */ struct userfaultfd_ctx { /* waitqueue head for the pending (i.e. not read) userfaults */ @@ -458,7 +468,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : TASK_KILLABLE; - spin_lock(&ctx->fault_pending_wqh.lock); + spin_lock_irq(&ctx->fault_pending_wqh.lock); /* * After the __add_wait_queue the uwq is visible to userland * through poll/read(). @@ -470,7 +480,7 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) * __add_wait_queue. */ set_current_state(blocking_state); - spin_unlock(&ctx->fault_pending_wqh.lock); + spin_unlock_irq(&ctx->fault_pending_wqh.lock); if (!is_vm_hugetlb_page(vmf->vma)) must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, @@ -552,13 +562,13 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) * kernel stack can be released after the list_del_init. */ if (!list_empty_careful(&uwq.wq.entry)) { - spin_lock(&ctx->fault_pending_wqh.lock); + spin_lock_irq(&ctx->fault_pending_wqh.lock); /* * No need of list_del_init(), the uwq on the stack * will be freed shortly anyway. */ list_del(&uwq.wq.entry); - spin_unlock(&ctx->fault_pending_wqh.lock); + spin_unlock_irq(&ctx->fault_pending_wqh.lock); } /* @@ -583,7 +593,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, init_waitqueue_entry(&ewq->wq, current); release_new_ctx = NULL; - spin_lock(&ctx->event_wqh.lock); + spin_lock_irq(&ctx->event_wqh.lock); /* * After the __add_wait_queue the uwq is visible to userland * through poll/read(). @@ -613,15 +623,15 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, break; } - spin_unlock(&ctx->event_wqh.lock); + spin_unlock_irq(&ctx->event_wqh.lock); wake_up_poll(&ctx->fd_wqh, EPOLLIN); schedule(); - spin_lock(&ctx->event_wqh.lock); + spin_lock_irq(&ctx->event_wqh.lock); } __set_current_state(TASK_RUNNING); - spin_unlock(&ctx->event_wqh.lock); + spin_unlock_irq(&ctx->event_wqh.lock); if (release_new_ctx) { struct vm_area_struct *vma; @@ -918,10 +928,10 @@ static int userfaultfd_release(struct inode *inode, struct file *file) * the last page faults that may have been already waiting on * the fault_*wqh. */ - spin_lock(&ctx->fault_pending_wqh.lock); + spin_lock_irq(&ctx->fault_pending_wqh.lock); __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range); - spin_unlock(&ctx->fault_pending_wqh.lock); + spin_unlock_irq(&ctx->fault_pending_wqh.lock); /* Flush pending events that may still wait on event_wqh */ wake_up_all(&ctx->event_wqh); @@ -1134,7 +1144,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, if (!ret && msg->event == UFFD_EVENT_FORK) { ret = resolve_userfault_fork(ctx, fork_nctx, msg); - spin_lock(&ctx->event_wqh.lock); + spin_lock_irq(&ctx->event_wqh.lock); if (!list_empty(&fork_event)) { /* * The fork thread didn't abort, so we can @@ -1180,7 +1190,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, if (ret) userfaultfd_ctx_put(fork_nctx); } - spin_unlock(&ctx->event_wqh.lock); + spin_unlock_irq(&ctx->event_wqh.lock); } return ret; @@ -1219,14 +1229,14 @@ static ssize_t userfaultfd_read(struct file *file, char __user *buf, static void __wake_userfault(struct userfaultfd_ctx *ctx, struct userfaultfd_wake_range *range) { - spin_lock(&ctx->fault_pending_wqh.lock); + spin_lock_irq(&ctx->fault_pending_wqh.lock); /* wake all in the range and autoremove */ if (waitqueue_active(&ctx->fault_pending_wqh)) __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, range); if (waitqueue_active(&ctx->fault_wqh)) __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range); - spin_unlock(&ctx->fault_pending_wqh.lock); + spin_unlock_irq(&ctx->fault_pending_wqh.lock); } static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, @@ -1881,7 +1891,7 @@ static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) wait_queue_entry_t *wq; unsigned long pending = 0, total = 0; - spin_lock(&ctx->fault_pending_wqh.lock); + spin_lock_irq(&ctx->fault_pending_wqh.lock); list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) { pending++; total++; @@ -1889,7 +1899,7 @@ static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) list_for_each_entry(wq, &ctx->fault_wqh.head, entry) { total++; } - spin_unlock(&ctx->fault_pending_wqh.lock); + spin_unlock_irq(&ctx->fault_pending_wqh.lock); /* * If more protocols will be added, there will be all shown -- 2.22.0 ^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-06-27 7:55 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-02-05 2:03 possible deadlock in io_submit_one syzbot 2019-03-11 13:23 ` syzbot 2019-06-12 19:48 ` Eric Biggers 2019-06-27 7:50 ` [PATCH] userfaultfd: disable irqs for fault_pending and event locks Eric Biggers
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