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SubjectINFO: task hung in vfat_lookup
From
Hello,

syzbot found the following crash on:

HEAD commit: 420f51f4ab6b Merge tag 'arm64-fixes' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11296c92400000
kernel config: https://syzkaller.appspot.com/x/.config?x=531a917630d2a492
dashboard link: https://syzkaller.appspot.com/bug?extid=72000baa7858f1703b04
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+72000baa7858f1703b04@syzkaller.appspotmail.com

INFO: task syz-executor0:4634 blocked for more than 140 seconds.
Not tainted 4.19.0-rc1+ #217
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0 D21248 4634 1 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2825 [inline]
__schedule+0x87c/0x1df0 kernel/sched/core.c:3473
schedule+0xfb/0x450 kernel/sched/core.c:3517
schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3575
__mutex_lock_common kernel/locking/mutex.c:1003 [inline]
__mutex_lock+0xbf9/0x1700 kernel/locking/mutex.c:1073
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1088
vfat_lookup+0xf1/0x640 fs/fat/namei_vfat.c:709
__lookup_slow+0x2b5/0x540 fs/namei.c:1671
lookup_slow+0x57/0x80 fs/namei.c:1688
walk_component+0x94a/0x2630 fs/namei.c:1810
link_path_walk.part.40+0xa6e/0x1540 fs/namei.c:2141
link_path_walk fs/namei.c:2072 [inline]
path_openat+0x268/0x5340 fs/namei.c:3533
do_filp_open+0x255/0x380 fs/namei.c:3564
do_sys_open+0x584/0x720 fs/open.c:1063
__do_sys_open fs/open.c:1081 [inline]
__se_sys_open fs/open.c:1076 [inline]
__x64_sys_open+0x7e/0xc0 fs/open.c:1076
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4551a0
Code: 44 24 10 48 8b 4c 24 08 48 8b 54 24 70 48 39 d0 0f 85 69 01 00 00 48
8b 9c 24 10 01 00 00 48 89 1c 24 48 89 54 24 08 48 89 4c <24> 10 48 89 44
24 18 e8 74 6d 00 00 0f b6 44 24 20 84 c0 0f 84 3c
RSP: 002b:00007ffd57125ec0 EFLAGS: 00000206 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004551a0
RDX: 0000000000000000 RSI: 0000000000090800 RDI: 00000000004c1e40
RBP: 00000000000001b6 R08: 0000000000000001 R09: 0000000001523940
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000003
R13: 0000000000051351 R14: 000000000000003a R15: badc0ffeebadface
INFO: task syz-executor0:8851 blocked for more than 140 seconds.
Not tainted 4.19.0-rc1+ #217
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor0 D23808 8851 4634 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2825 [inline]
__schedule+0x87c/0x1df0 kernel/sched/core.c:3473
schedule+0xfb/0x450 kernel/sched/core.c:3517
d_wait_lookup fs/dcache.c:2428 [inline]
d_alloc_parallel+0x1456/0x1eb0 fs/dcache.c:2510
__lookup_slow+0x1e6/0x540 fs/namei.c:1654
lookup_slow+0x57/0x80 fs/namei.c:1688
walk_component+0x94a/0x2630 fs/namei.c:1810
link_path_walk.part.40+0xa6e/0x1540 fs/namei.c:2141
link_path_walk fs/namei.c:2072 [inline]
path_openat+0x268/0x5340 fs/namei.c:3533
do_filp_open+0x255/0x380 fs/namei.c:3564
do_sys_open+0x584/0x720 fs/open.c:1063
__do_sys_open fs/open.c:1081 [inline]
__se_sys_open fs/open.c:1076 [inline]
__x64_sys_open+0x7e/0xc0 fs/open.c:1076
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x410dd1
Code: 00 00 00 00 00 00 00 48 c7 84 24 90 00 00 00 00 00 00 00 48 8d 05 0f
5e 04 00 48 89 44 24 78 48 8d 44 24 50 48 89 84 24 80 00 <00> 00 48 8d 84
24 a8 00 00 00 48 89 84 24 88 00 00 00 0f b6 84 24
RSP: 002b:00007f0a65bafbb0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f0a65bb06d4 RCX: 0000000000410dd1
RDX: 00007f0a65bafbe2 RSI: 0000000000000002 RDI: 00007f0a65bafbd0
RBP: 0000000000930140 R08: 0000000000000000 R09: 0000000000000012
R10: 0000000000000007 R11: 0000000000000293 R12: 00000000ffffffff
R13: 00000000004d72c0 R14: 00000000004ca44c R15: 0000000000000001

Showing all locks held in the system:
1 lock held by khungtaskd/792:
#0: 00000000d6534971 (rcu_read_lock){....}, at:
debug_show_all_locks+0xd0/0x428 kernel/locking/lockdep.c:4436
1 lock held by rsyslogd/4498:
2 locks held by getty/4588:
#0: 000000001a00424d (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:353
#1: 0000000064c91a05 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4589:
#0: 0000000044cc0e87 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:353
#1: 0000000031085714 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4590:
#0: 00000000a90082dc (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:353
#1: 00000000dcf02824 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4591:
#0: 000000003298bfed (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:353
#1: 0000000065469fb5 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4592:
#0: 00000000c527c2cb (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:353
#1: 000000006b71748e (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4593:
#0: 000000007d73fabd (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:353
#1: 00000000e3e6d879 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4594:
#0: 00000000c6a3fd33 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:353
#1: 000000003e69bf2b (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by syz-executor0/4634:
#0: 00000000cc4e26bc (&sb->s_type->i_mutex_key#22){++++}, at:
inode_lock_shared include/linux/fs.h:748 [inline]
#0: 00000000cc4e26bc (&sb->s_type->i_mutex_key#22){++++}, at:
lookup_slow+0x49/0x80 fs/namei.c:1687
#1: 00000000a76b47cf (&sbi->s_lock){+.+.}, at: vfat_lookup+0xf1/0x640
fs/fat/namei_vfat.c:709
2 locks held by syz-executor0/8846:
1 lock held by syz-executor0/8851:
#0: 00000000cc4e26bc (&sb->s_type->i_mutex_key#22){++++}, at:
inode_lock_shared include/linux/fs.h:748 [inline]
#0: 00000000cc4e26bc (&sb->s_type->i_mutex_key#22){++++}, at:
lookup_slow+0x49/0x80 fs/namei.c:1687

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

NMI backtrace for cpu 1
CPU: 1 PID: 792 Comm: khungtaskd Not tainted 4.19.0-rc1+ #217
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+0x1c9/0x2b4 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.3+0x48/0x88 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:144 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline]
watchdog+0xb39/0x1040 kernel/hung_task.c:265
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413
Sending NMI from CPU 1 to CPUs 0:
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.030
msecs
NMI backtrace for cpu 0
CPU: 0 PID: 8846 Comm: syz-executor0 Not tainted 4.19.0-rc1+ #217
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:find_get_entry+0x304/0xc90 mm/filemap.c:1424
Code: c2 3b 0d 9b 81 e8 4c 90 c4 ff 48 b8 00 00 00 00 00 fc ff df 48 03 85
d0 fc ff ff 48 8d 78 08 48 c7 00 00 00 00 00 48 83 e7 f8 <48> c7 40 48 00
00 00 00 48 29 f8 8d 48 50 31 c0 c1 e9 03 f3 48 ab
RSP: 0018:ffff8801824de488 EFLAGS: 00000286
RAX: ffffed003049bc9f RBX: 0000000000000001 RCX: 1ffff1003b35b50e
RDX: 1ffffffff10237b5 RSI: 0000000000000003 RDI: ffffed003049bca0
RBP: ffff8801824de7c0 R08: 1ffff1003049bc72 R09: ffffed003b6046de
R10: 0000000000000003 R11: 0000000000000002 R12: ffffea00070312c0
R13: ffff8801824de798 R14: 0000000000000000 R15: dffffc0000000000
FS: 00007f0a65bd1700(0000) GS:ffff8801db000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 000000018732e000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
pagecache_get_page+0x11e/0xe40 mm/filemap.c:1541
find_or_create_page include/linux/pagemap.h:322 [inline]
grow_dev_page fs/buffer.c:948 [inline]
grow_buffers fs/buffer.c:1017 [inline]
__getblk_slow fs/buffer.c:1044 [inline]
__getblk_gfp+0x3bb/0xb10 fs/buffer.c:1321
__bread_gfp+0x2d/0x310 fs/buffer.c:1355
sb_bread include/linux/buffer_head.h:307 [inline]
fat__get_entry+0x59c/0xa30 fs/fat/dir.c:101
fat_get_entry fs/fat/dir.c:129 [inline]
fat_search_long+0x33b/0x15d0 fs/fat/dir.c:477
vfat_find+0x16d/0x1a0 fs/fat/namei_vfat.c:697
vfat_lookup+0x107/0x640 fs/fat/namei_vfat.c:711
__lookup_slow+0x2b5/0x540 fs/namei.c:1671
lookup_slow+0x57/0x80 fs/namei.c:1688
walk_component+0x94a/0x2630 fs/namei.c:1810
link_path_walk.part.40+0xa6e/0x1540 fs/namei.c:2141
link_path_walk fs/namei.c:2072 [inline]
path_openat+0x268/0x5340 fs/namei.c:3533
do_filp_open+0x255/0x380 fs/namei.c:3564
do_sys_open+0x584/0x720 fs/open.c:1063
__do_sys_open fs/open.c:1081 [inline]
__se_sys_open fs/open.c:1076 [inline]
__x64_sys_open+0x7e/0xc0 fs/open.c:1076
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x410dd1
Code: 75 14 b8 02 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 b4 17 00 00 c3 48
83 ec 08 e8 8a fa ff ff 48 89 04 24 b8 02 00 00 00 0f 05 <48> 8b 3c 24 48
89 c2 e8 d3 fa ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007f0a65bd0bb0 EFLAGS: 00000293 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007f0a65bd16d4 RCX: 0000000000410dd1
RDX: 00007f0a65bd0be2 RSI: 0000000000000002 RDI: 00007f0a65bd0bd0
RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000012
R10: 0000000000000007 R11: 0000000000000293 R12: 00000000ffffffff
R13: 00000000004d72c0 R14: 00000000004ca44c R15: 0000000000000000


---
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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