[syzbot] INFO: task hung in fuse_launder_page

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 36a21d51725a Linux 5.14-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=104b8eaa300000
kernel config: https://syzkaller.appspot.com/x/.config?x=e3a20bae04b96ccd
dashboard link: https://syzkaller.appspot.com/bug?extid=bea44a5189836d956894
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=143c0ee9300000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=158fc9aa300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bea44a...@syzkaller.appspotmail.com

INFO: task syz-executor276:8433 blocked for more than 143 seconds.
Not tainted 5.14.0-rc5-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor276 state:D stack:27736 pid: 8433 ppid: 8430 flags:0x00004004
Call Trace:
context_switch kernel/sched/core.c:4681 [inline]
__schedule+0x93a/0x26f0 kernel/sched/core.c:5938
schedule+0xd3/0x270 kernel/sched/core.c:6017
fuse_wait_on_page_writeback fs/fuse/file.c:452 [inline]
fuse_wait_on_page_writeback+0x120/0x170 fs/fuse/file.c:448
fuse_launder_page fs/fuse/file.c:2316 [inline]
fuse_launder_page+0xe9/0x130 fs/fuse/file.c:2306
do_launder_page mm/truncate.c:595 [inline]
invalidate_inode_pages2_range+0x994/0xf80 mm/truncate.c:661
fuse_finish_open+0x2d9/0x560 fs/fuse/file.c:202
fuse_open_common+0x2f9/0x4c0 fs/fuse/file.c:254
do_dentry_open+0x4c8/0x11d0 fs/open.c:826
do_open fs/namei.c:3374 [inline]
path_openat+0x1c23/0x27f0 fs/namei.c:3507
do_filp_open+0x1aa/0x400 fs/namei.c:3534
do_sys_openat2+0x16d/0x420 fs/open.c:1204
do_sys_open fs/open.c:1220 [inline]
__do_sys_creat fs/open.c:1294 [inline]
__se_sys_creat fs/open.c:1288 [inline]
__x64_sys_creat+0xc9/0x120 fs/open.c:1288
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+0x44/0xae
RIP: 0033:0x446409
RSP: 002b:00007f0e6a9f92f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00000000004d34f0 RCX: 0000000000446409
RDX: 0000000000446409 RSI: 0000000000000000 RDI: 0000000020000280
RBP: 00000000004a3164 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 000000000049f158 R14: 00000000004a1160 R15: 00000000004d34f8

Showing all locks held in the system:
1 lock held by khungtaskd/1584:
#0: ffffffff8b97c1c0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6446
2 locks held by syz-executor276/8433:
#0: ffff888015e38460 (sb_writers#11){.+.+}-{0:0}, at: do_open fs/namei.c:3367 [inline]
#0: ffff888015e38460 (sb_writers#11){.+.+}-{0:0}, at: path_openat+0x1aee/0x27f0 fs/namei.c:3507
#1: ffff8880397d0150 (&sb->s_type->i_mutex_key#17){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:774 [inline]
#1: ffff8880397d0150 (&sb->s_type->i_mutex_key#17){+.+.}-{3:3}, at: fuse_open_common+0x366/0x4c0 fs/fuse/file.c:241

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 1584 Comm: khungtaskd Not tainted 5.14.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105
nmi_cpu_backtrace.cold+0x44/0xd7 lib/nmi_backtrace.c:105
nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
watchdog+0xd0a/0xfc0 kernel/hung_task.c:295
kthread+0x3e5/0x4d0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_safe_halt drivers/acpi/processor_idle.c:109 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_idle_do_entry+0x1c6/0x250 drivers/acpi/processor_idle.c:553


---
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[Miklos Szeredi]

Attached patch should fix this.

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
master

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+bea44a...@syzkaller.appspotmail.com

Tested on:

commit: 794c7931 Merge branch 'linus' of git://git.kernel.org/..
git tree: upstream
kernel config: https://syzkaller.appspot.com/x/.config?x=96f0602203250753

dashboard link: https://syzkaller.appspot.com/bug?extid=bea44a5189836d956894
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1

patch: https://syzkaller.appspot.com/x/patch.diff?x=169e4131300000

Note: testing is done by a robot and is best-effort only.