[syzbot] possible deadlock in __schedule

From: syzbot
Date: Mon May 17 2021 - 05:32:30 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 88b06399 Merge tag 'for-5.13-rc1-part2-tag' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11d47145d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=e4fa783e79fe30c8
dashboard link: https://syzkaller.appspot.com/bug?extid=a9bb2f97117a3bb1b77d

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a9bb2f97117a3bb1b77d@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
5.13.0-rc1-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/9979 is trying to acquire lock:
ffff88803ffffba0 (&pgdat->kswapd_wait){..-.}-{2:2}, at: __wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137

but task is already holding lock:
ffff88802cd35358 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1334 [inline]
ffff88802cd35358 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x21c/0x23e0 kernel/sched/core.c:5061

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&rq->lock){-.-.}-{2:2}:
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:151
rq_lock kernel/sched/sched.h:1334 [inline]
task_fork_fair+0x74/0x4d0 kernel/sched/fair.c:10795
sched_fork+0x3fc/0xbd0 kernel/sched/core.c:3792
copy_process+0x1f32/0x7120 kernel/fork.c:2086
kernel_clone+0xe7/0xab0 kernel/fork.c:2503
kernel_thread+0xb5/0xf0 kernel/fork.c:2555
rest_init+0x23/0x388 init/main.c:687
start_kernel+0x475/0x496 init/main.c:1087
secondary_startup_64_no_verify+0xb0/0xbb

-> #1 (&p->pi_lock){-.-.}-{2:2}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
try_to_wake_up+0x98/0x14b0 kernel/sched/core.c:3364
autoremove_wake_function+0x12/0x140 kernel/sched/wait.c:404
__wake_up_common+0x147/0x650 kernel/sched/wait.c:108
__wake_up_common_lock+0xd0/0x130 kernel/sched/wait.c:138
wakeup_kswapd+0x3f8/0x640 mm/vmscan.c:4185
rmqueue mm/page_alloc.c:3572 [inline]
get_page_from_freelist+0x17bd/0x2b60 mm/page_alloc.c:3991
__alloc_pages+0x1b2/0x500 mm/page_alloc.c:5200
alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
__page_cache_alloc mm/filemap.c:1005 [inline]
__page_cache_alloc+0x303/0x3a0 mm/filemap.c:990
pagecache_get_page+0x38f/0x18d0 mm/filemap.c:1885
grab_cache_page_write_begin+0x64/0x90 mm/filemap.c:3610
ext4_da_write_begin+0x35c/0x1160 fs/ext4/inode.c:2984
generic_perform_write+0x20a/0x4f0 mm/filemap.c:3660
ext4_buffered_write_iter+0x244/0x4d0 fs/ext4/file.c:269
ext4_file_write_iter+0x423/0x14e0 fs/ext4/file.c:680
call_write_iter include/linux/fs.h:2114 [inline]
new_sync_write+0x426/0x650 fs/read_write.c:518
vfs_write+0x796/0xa30 fs/read_write.c:605
ksys_write+0x12d/0x250 fs/read_write.c:658
do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #0 (&pgdat->kswapd_wait){..-.}-{2:2}:
check_prev_add kernel/locking/lockdep.c:2938 [inline]
check_prevs_add kernel/locking/lockdep.c:3061 [inline]
validate_chain kernel/locking/lockdep.c:3676 [inline]
__lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4902
lock_acquire kernel/locking/lockdep.c:5512 [inline]
lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5477
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
__wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137
wakeup_kswapd+0x3f8/0x640 mm/vmscan.c:4185
wake_all_kswapds+0x143/0x2c0 mm/page_alloc.c:4484
__alloc_pages_slowpath.constprop.0+0x17c1/0x2140 mm/page_alloc.c:4756
__alloc_pages+0x422/0x500 mm/page_alloc.c:5213
alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
stack_depot_save+0x39d/0x4e0 lib/stackdepot.c:303
kasan_save_stack+0x32/0x40 mm/kasan/common.c:40
kasan_record_aux_stack+0xa4/0xd0 mm/kasan/generic.c:345
irq_work_queue_on+0x9f/0x160 kernel/irq_work.c:104
balance_rt+0x202/0x2c0 kernel/sched/rt.c:1541
put_prev_task_balance kernel/sched/core.c:4934 [inline]
pick_next_task kernel/sched/core.c:4974 [inline]
__schedule+0x134c/0x23e0 kernel/sched/core.c:5111
schedule+0xcf/0x270 kernel/sched/core.c:5226
schedule_timeout+0x14a/0x250 kernel/time/timer.c:1892
io_schedule_timeout+0xcb/0x140 kernel/sched/core.c:7203
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common_io kernel/sched/completion.c:123 [inline]
wait_for_completion_io_timeout+0x163/0x280 kernel/sched/completion.c:191
submit_bio_wait+0x158/0x230 block/bio.c:1160
blkdev_issue_flush+0xd6/0x130 block/blk-flush.c:446
ext4_sync_file+0x60b/0xfd0 fs/ext4/fsync.c:177
vfs_fsync_range+0x13a/0x220 fs/sync.c:200
generic_write_sync include/linux/fs.h:2982 [inline]
ext4_buffered_write_iter+0x36a/0x4d0 fs/ext4/file.c:277
ext4_file_write_iter+0x423/0x14e0 fs/ext4/file.c:680
call_write_iter include/linux/fs.h:2114 [inline]
do_iter_readv_writev+0x46f/0x740 fs/read_write.c:740
do_iter_write+0x188/0x670 fs/read_write.c:866
vfs_iter_write+0x70/0xa0 fs/read_write.c:907
iter_file_splice_write+0x6fa/0xc10 fs/splice.c:689
do_splice_from fs/splice.c:767 [inline]
direct_splice_actor+0x110/0x180 fs/splice.c:936
splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891
do_splice_direct+0x1b3/0x280 fs/splice.c:979
do_sendfile+0x9f0/0x1110 fs/read_write.c:1260
__do_sys_sendfile64 fs/read_write.c:1319 [inline]
__se_sys_sendfile64 fs/read_write.c:1311 [inline]
__x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1311
do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

other info that might help us debug this:

Chain exists of:
&pgdat->kswapd_wait --> &p->pi_lock --> &rq->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&rq->lock);
lock(&p->pi_lock);
lock(&rq->lock);
lock(&pgdat->kswapd_wait);

*** DEADLOCK ***

2 locks held by syz-executor.0/9979:
#0: ffff888023830460 (sb_writers#5){.+.+}-{0:0}, at: __do_sys_sendfile64 fs/read_write.c:1319 [inline]
#0: ffff888023830460 (sb_writers#5){.+.+}-{0:0}, at: __se_sys_sendfile64 fs/read_write.c:1311 [inline]
#0: ffff888023830460 (sb_writers#5){.+.+}-{0:0}, at: __x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1311
#1: ffff88802cd35358 (&rq->lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1334 [inline]
#1: ffff88802cd35358 (&rq->lock){-.-.}-{2:2}, at: __schedule+0x21c/0x23e0 kernel/sched/core.c:5061

stack backtrace:
CPU: 3 PID: 9979 Comm: syz-executor.0 Not tainted 5.13.0-rc1-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2129
check_prev_add kernel/locking/lockdep.c:2938 [inline]
check_prevs_add kernel/locking/lockdep.c:3061 [inline]
validate_chain kernel/locking/lockdep.c:3676 [inline]
__lock_acquire+0x2a17/0x5230 kernel/locking/lockdep.c:4902
lock_acquire kernel/locking/lockdep.c:5512 [inline]
lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5477
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
__wake_up_common_lock+0xb4/0x130 kernel/sched/wait.c:137
wakeup_kswapd+0x3f8/0x640 mm/vmscan.c:4185
wake_all_kswapds+0x143/0x2c0 mm/page_alloc.c:4484
__alloc_pages_slowpath.constprop.0+0x17c1/0x2140 mm/page_alloc.c:4756
__alloc_pages+0x422/0x500 mm/page_alloc.c:5213
alloc_pages+0x18c/0x2a0 mm/mempolicy.c:2272
stack_depot_save+0x39d/0x4e0 lib/stackdepot.c:303
kasan_save_stack+0x32/0x40 mm/kasan/common.c:40
kasan_record_aux_stack+0xa4/0xd0 mm/kasan/generic.c:345
irq_work_queue_on+0x9f/0x160 kernel/irq_work.c:104
balance_rt+0x202/0x2c0 kernel/sched/rt.c:1541
put_prev_task_balance kernel/sched/core.c:4934 [inline]
pick_next_task kernel/sched/core.c:4974 [inline]
__schedule+0x134c/0x23e0 kernel/sched/core.c:5111
schedule+0xcf/0x270 kernel/sched/core.c:5226
schedule_timeout+0x14a/0x250 kernel/time/timer.c:1892
io_schedule_timeout+0xcb/0x140 kernel/sched/core.c:7203
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common_io kernel/sched/completion.c:123 [inline]
wait_for_completion_io_timeout+0x163/0x280 kernel/sched/completion.c:191
submit_bio_wait+0x158/0x230 block/bio.c:1160
blkdev_issue_flush+0xd6/0x130 block/blk-flush.c:446
ext4_sync_file+0x60b/0xfd0 fs/ext4/fsync.c:177
vfs_fsync_range+0x13a/0x220 fs/sync.c:200
generic_write_sync include/linux/fs.h:2982 [inline]
ext4_buffered_write_iter+0x36a/0x4d0 fs/ext4/file.c:277
ext4_file_write_iter+0x423/0x14e0 fs/ext4/file.c:680
call_write_iter include/linux/fs.h:2114 [inline]
do_iter_readv_writev+0x46f/0x740 fs/read_write.c:740
do_iter_write+0x188/0x670 fs/read_write.c:866
vfs_iter_write+0x70/0xa0 fs/read_write.c:907
iter_file_splice_write+0x6fa/0xc10 fs/splice.c:689
do_splice_from fs/splice.c:767 [inline]
direct_splice_actor+0x110/0x180 fs/splice.c:936
splice_direct_to_actor+0x34b/0x8c0 fs/splice.c:891
do_splice_direct+0x1b3/0x280 fs/splice.c:979
do_sendfile+0x9f0/0x1110 fs/read_write.c:1260
__do_sys_sendfile64 fs/read_write.c:1319 [inline]
__se_sys_sendfile64 fs/read_write.c:1311 [inline]
__x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1311
do_syscall_64+0x3a/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665f9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f354f1c3188 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 000000000056c158 RCX: 00000000004665f9
RDX: 0000000020000100 RSI: 0000000000000006 RDI: 0000000000000006
RBP: 00000000004bfce1 R08: 0000000000000000 R09: 0000000000000000
R10: 00008080ffffff80 R11: 0000000000000246 R12: 000000000056c158
R13: 00007fff4004641f R14: 00007f354f1c3300 R15: 0000000000022000

---
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