[PATCH 5.10 098/157] io_uring: fix inconsistent lock state

Greg Kroah-Hartman
2021-03-22T12:49:02Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit 9ae1f8dd372e0e4c020b345cf9e09f519265e981 ]

WARNING: inconsistent lock state

inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
syz-executor217/8450 [HC1[1]:SC0[0]:HE0:SE1] takes:
ffff888023d6e620 (&fs->lock){?.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:354 [inline]
ffff888023d6e620 (&fs->lock){?.+.}-{2:2}, at: io_req_clean_work fs/io_uring.c:1398 [inline]
ffff888023d6e620 (&fs->lock){?.+.}-{2:2}, at: io_dismantle_req+0x66f/0xf60 fs/io_uring.c:2029

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&fs->lock);
<Interrupt>
lock(&fs->lock);

*** DEADLOCK ***

1 lock held by syz-executor217/8450:
#0: ffff88802417c3e8 (&ctx->uring_lock){+.+.}-{3:3}, at: __do_sys_io_uring_enter+0x1071/0x1f30 fs/io_uring.c:9442

stack backtrace:
CPU: 1 PID: 8450 Comm: syz-executor217 Not tainted 5.11.0-rc5-next-20210129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
[...]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:354 [inline]
io_req_clean_work fs/io_uring.c:1398 [inline]
io_dismantle_req+0x66f/0xf60 fs/io_uring.c:2029
__io_free_req+0x3d/0x2e0 fs/io_uring.c:2046
io_free_req fs/io_uring.c:2269 [inline]
io_double_put_req fs/io_uring.c:2392 [inline]
io_put_req+0xf9/0x570 fs/io_uring.c:2388
io_link_timeout_fn+0x30c/0x480 fs/io_uring.c:6497
__run_hrtimer kernel/time/hrtimer.c:1519 [inline]
__hrtimer_run_queues+0x609/0xe40 kernel/time/hrtimer.c:1583
hrtimer_interrupt+0x334/0x940 kernel/time/hrtimer.c:1645
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1085 [inline]
__sysvec_apic_timer_interrupt+0x146/0x540 arch/x86/kernel/apic/apic.c:1102
asm_call_irq_on_stack+0xf/0x20
</IRQ>
__run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline]
run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline]
sysvec_apic_timer_interrupt+0xbd/0x100 arch/x86/kernel/apic/apic.c:1096
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:629
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x25/0x40 kernel/locking/spinlock.c:199
spin_unlock_irq include/linux/spinlock.h:404 [inline]
io_queue_linked_timeout+0x194/0x1f0 fs/io_uring.c:6525
__io_queue_sqe+0x328/0x1290 fs/io_uring.c:6594
io_queue_sqe+0x631/0x10d0 fs/io_uring.c:6639
io_queue_link_head fs/io_uring.c:6650 [inline]
io_submit_sqe fs/io_uring.c:6697 [inline]
io_submit_sqes+0x19b5/0x2720 fs/io_uring.c:6960
__do_sys_io_uring_enter+0x107d/0x1f30 fs/io_uring.c:9443
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Don't free requests from under hrtimer context (softirq) as it may sleep
or take spinlocks improperly (e.g. non-irq versions).

Cc: stable@vger.kernel.org # 5.6+
Reported-by: syzbot+81d17233a2b02eafba33@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index dcc77af5320e..5746998799ab 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6234,9 +6234,10 @@ static enum hrtimer_restart io_link_timeout_fn(struct hrtimer *timer)
if (prev) {
req_set_fail_links(prev);
io_async_find_and_cancel(ctx, req, prev->user_data, -ETIME);
- io_put_req(prev);
+ io_put_req_deferred(prev, 1);
} else {
- io_req_complete(req, -ETIME);
+ io_cqring_add_event(req, -ETIME, 0);
+ io_put_req_deferred(req, 1);
}
return HRTIMER_NORESTART;
}
--
2.30.1