Re: [syzbot] possible deadlock in throtl_pending_timer_fn

From: syzbot
Date: Fri Jul 29 2022 - 19:32:30 EST

Next message: Stephen Boyd: "Re: [PATCH v3 00/11] drm/msm/dsi_phy: Replace parent names with clk_hw pointers"
Previous message: Jason A. Donenfeld: "Re: [PATCH 2/2 v2] lib/vsprintf: Initialize vsprintf's pointer hash once the random core is ready."
Next in thread: syzbot: "Re: [syzbot] possible deadlock in throtl_pending_timer_fn"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

syzbot has found a reproducer for the following issue on:

HEAD commit: cb71b93c2dc3 Add linux-next specific files for 20220628
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=154438f2080000
kernel config: https://syzkaller.appspot.com/x/.config?x=badbc1adb2d582eb
dashboard link: https://syzkaller.appspot.com/bug?extid=934ebb67352c8a490bf3
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17713dee080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15d24952080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+934ebb67352c8a490bf3@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
5.19.0-rc4-next-20220628-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor358/3597 is trying to acquire lock:
ffff888146f83aa0 (&q->queue_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:385 [inline]
ffff888146f83aa0 (&q->queue_lock){..-.}-{2:2}, at: throtl_pending_timer_fn+0xf7/0x1690 block/blk-throttle.c:1152

but task is already holding lock:
ffffc900001e0d70 ((&sq->pending_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:31 [inline]
ffffc900001e0d70 ((&sq->pending_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd5/0x6b0 kernel/time/timer.c:1464

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 ((&sq->pending_timer)){+.-.}-{0:0}:
del_timer_sync+0x5b/0x1b0 kernel/time/timer.c:1417
throtl_pd_free+0x15/0x40 block/blk-throttle.c:500
blkcg_deactivate_policy block/blk-cgroup.c:1520 [inline]
blkcg_deactivate_policy+0x2d2/0x4e0 block/blk-cgroup.c:1498
blk_throtl_exit+0x8a/0x1a0 block/blk-throttle.c:2336
blkcg_init_queue+0x19b/0x620 block/blk-cgroup.c:1301
__alloc_disk_node+0x260/0x610 block/genhd.c:1365
__blk_mq_alloc_disk+0x133/0x1c0 block/blk-mq.c:3927
loop_add+0x3e2/0xaf0 drivers/block/loop.c:1978
loop_control_ioctl+0x133/0x540 drivers/block/loop.c:2151
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0

-> #1 (&blkcg->lock){....}-{2:2}:
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:360 [inline]
blkg_create+0x45e/0x1000 block/blk-cgroup.c:344
blkcg_init_queue+0xb2/0x620 block/blk-cgroup.c:1282
__alloc_disk_node+0x260/0x610 block/genhd.c:1365
__blk_alloc_disk+0x35/0x70 block/genhd.c:1405
brd_alloc.part.0+0x27f/0x7a0 drivers/block/brd.c:391
brd_alloc drivers/block/brd.c:374 [inline]
brd_init+0x1b8/0x24b drivers/block/brd.c:477
do_one_initcall+0xfe/0x650 init/main.c:1300
do_initcall_level init/main.c:1375 [inline]
do_initcalls init/main.c:1391 [inline]
do_basic_setup init/main.c:1410 [inline]
kernel_init_freeable+0x6b1/0x73a init/main.c:1617
kernel_init+0x1a/0x1d0 init/main.c:1506
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302

-> #0 (&q->queue_lock){..-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3829 [inline]
__lock_acquire+0x2abe/0x5660 kernel/locking/lockdep.c:5053
lock_acquire kernel/locking/lockdep.c:5665 [inline]
lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5630
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:385 [inline]
throtl_pending_timer_fn+0xf7/0x1690 block/blk-throttle.c:1152
call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474
expire_timers kernel/time/timer.c:1519 [inline]
__run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790
__run_timers kernel/time/timer.c:1768 [inline]
run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803
__do_softirq+0x29b/0x9c2 kernel/softirq.c:571
invoke_softirq kernel/softirq.c:445 [inline]
__irq_exit_rcu+0x123/0x180 kernel/softirq.c:650
irq_exit_rcu+0x5/0x20 kernel/softirq.c:662
sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1106
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:649
lock_acquire+0x1ef/0x570 kernel/locking/lockdep.c:5633
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:360 [inline]
new_inode_pseudo fs/inode.c:1022 [inline]
new_inode+0x48/0x270 fs/inode.c:1047
debugfs_get_inode+0x1a/0x130 fs/debugfs/inode.c:72
debugfs_create_dir+0xdc/0x4d0 fs/debugfs/inode.c:578
bdi_debug_register mm/backing-dev.c:112 [inline]
bdi_register_va.part.0+0x22d/0x800 mm/backing-dev.c:880
bdi_register_va mm/backing-dev.c:908 [inline]
bdi_register+0x12a/0x140 mm/backing-dev.c:905
device_add_disk+0x83c/0xe20 block/genhd.c:513
add_disk include/linux/blkdev.h:768 [inline]
loop_add+0x884/0xaf0 drivers/block/loop.c:2031
loop_control_ioctl+0x133/0x540 drivers/block/loop.c:2151
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0

other info that might help us debug this:

Chain exists of:
&q->queue_lock --> &blkcg->lock --> (&sq->pending_timer)

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock((&sq->pending_timer));
lock(&blkcg->lock);
lock((&sq->pending_timer));
lock(&q->queue_lock);

*** DEADLOCK ***

3 locks held by syz-executor358/3597:
#0: ffff888140c48b70 (&sb->s_type->i_mutex_key#3){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:761 [inline]
#0: ffff888140c48b70 (&sb->s_type->i_mutex_key#3){+.+.}-{3:3}, at: start_creating.part.0+0xb2/0x280 fs/debugfs/inode.c:348
#1: ffff8880761cf340 (&sb->s_type->i_lock_key#7){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:360 [inline]
#1: ffff8880761cf340 (&sb->s_type->i_lock_key#7){+.+.}-{2:2}, at: new_inode_pseudo fs/inode.c:1022 [inline]
#1: ffff8880761cf340 (&sb->s_type->i_lock_key#7){+.+.}-{2:2}, at: new_inode+0x48/0x270 fs/inode.c:1047
#2: ffffc900001e0d70 ((&sq->pending_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:31 [inline]
#2: ffffc900001e0d70 ((&sq->pending_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd5/0x6b0 kernel/time/timer.c:1464

stack backtrace:
CPU: 1 PID: 3597 Comm: syz-executor358 Not tainted 5.19.0-rc4-next-20220628-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3829 [inline]
__lock_acquire+0x2abe/0x5660 kernel/locking/lockdep.c:5053
lock_acquire kernel/locking/lockdep.c:5665 [inline]
lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5630
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:385 [inline]
throtl_pending_timer_fn+0xf7/0x1690 block/blk-throttle.c:1152
call_timer_fn+0x1a0/0x6b0 kernel/time/timer.c:1474
expire_timers kernel/time/timer.c:1519 [inline]
__run_timers.part.0+0x674/0xa80 kernel/time/timer.c:1790
__run_timers kernel/time/timer.c:1768 [inline]
run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1803
__do_softirq+0x29b/0x9c2 kernel/softirq.c:571
invoke_softirq kernel/softirq.c:445 [inline]
__irq_exit_rcu+0x123/0x180 kernel/softirq.c:650
irq_exit_rcu+0x5/0x20 kernel/softirq.c:662
sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1106
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1b/0x20 arch/x86/include/asm/idtentry.h:649
RIP: 0010:lock_acquire+0x1ef/0x570 kernel/locking/lockdep.c:5633
Code: e7 a3 7e 83 f8 01 0f 85 e8 02 00 00 9c 58 f6 c4 02 0f 85 fb 02 00 00 48 83 7c 24 08 00 74 01 fb 48 b8 00 00 00 00 00 fc ff df <48> 01 c3 48 c7 03 00 00 00 00 48 c7 43 08 00 00 00 00 48 8b 84 24
RSP: 0018:ffffc90002fffaa0 EFLAGS: 00000206
RAX: dffffc0000000000 RBX: 1ffff920005fff56 RCX: ffffffff815e3c0e
RDX: 1ffff11004088899 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff906a5967
R10: fffffbfff20d4b2c R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: ffff8880761cf340 R15: 0000000000000000
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:360 [inline]
new_inode_pseudo fs/inode.c:1022 [inline]
new_inode+0x48/0x270 fs/inode.c:1047
debugfs_get_inode+0x1a/0x130 fs/debugfs/inode.c:72
debugfs_create_dir+0xdc/0x4d0 fs/debugfs/inode.c:578
bdi_debug_register mm/backing-dev.c:112 [inline]
bdi_register_va.part.0+0x22d/0x800 mm/backing-dev.c:880
bdi_register_va mm/backing-dev.c:908 [inline]
bdi_register+0x12a/0x140 mm/backing-dev.c:905
device_add_disk+0x83c/0xe20 block/genhd.c:513
add_disk include/linux/blkdev.h:768 [inline]
loop_add+0x884/0xaf0 drivers/block/loop.c:2031
loop_control_ioctl+0x133/0x540 drivers/block/loop.c:2151
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f92d80b4079
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 90 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcc0861258 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f92d80b4079
RDX: 0000000000000000 RSI: 0000000000004c80 RDI: 0000000000000003
RBP: 00007ffcc0861270 R08: 0000000000000002 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 431bde82d7b634db R14: 0000000000000000 R15: 0000000000000000
</TASK>
----------------
Code disassembly (best guess):
0: e7 a3 out %eax,$0xa3
2: 7e 83 jle 0xffffff87
4: f8 clc
5: 01 0f add %ecx,(%rdi)
7: 85 e8 test %ebp,%eax
9: 02 00 add (%rax),%al
b: 00 9c 58 f6 c4 02 0f add %bl,0xf02c4f6(%rax,%rbx,2)
12: 85 fb test %edi,%ebx
14: 02 00 add (%rax),%al
16: 00 48 83 add %cl,-0x7d(%rax)
19: 7c 24 jl 0x3f
1b: 08 00 or %al,(%rax)
1d: 74 01 je 0x20
1f: fb sti
20: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
27: fc ff df
* 2a: 48 01 c3 add %rax,%rbx <-- trapping instruction
2d: 48 c7 03 00 00 00 00 movq $0x0,(%rbx)
34: 48 c7 43 08 00 00 00 movq $0x0,0x8(%rbx)
3b: 00
3c: 48 rex.W
3d: 8b .byte 0x8b
3e: 84 .byte 0x84
3f: 24 .byte 0x24

Next message: Stephen Boyd: "Re: [PATCH v3 00/11] drm/msm/dsi_phy: Replace parent names with clk_hw pointers"
Previous message: Jason A. Donenfeld: "Re: [PATCH 2/2 v2] lib/vsprintf: Initialize vsprintf's pointer hash once the random core is ready."
Next in thread: syzbot: "Re: [syzbot] possible deadlock in throtl_pending_timer_fn"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]