INFO: task hung in grab_super (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 93c338c2 Merge 4.14.129 into android-4.14
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=111682dea00000
kernel config: https://syzkaller.appspot.com/x/.config?x=654d6d7c478db79
dashboard link: https://syzkaller.appspot.com/bug?extid=8a497943f38daf6bd197
compiler: gcc (GCC) 9.0.0 20181231 (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+8a4979...@syzkaller.appspotmail.com

audit: type=1400 audit(1022.087:26964): avc: denied { map } for
pid=28272 comm="sh" path="/bin/dash" dev="sda1" ino=1473
scontext=system_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
ip6_tunnel: ip6tnl1 xmit: Local address not yet configured!
ip6_tunnel: ip6tnl1 xmit: Local address not yet configured!
INFO: task syz-executor.1:28235 blocked for more than 140 seconds.
Not tainted 4.14.129+ #11
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D27960 28235 1845 0x00000004
Call Trace:
schedule+0x92/0x1c0 kernel/sched/core.c:3498
__rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:588 [inline]
rwsem_down_write_failed+0x3b1/0x760 kernel/locking/rwsem-xadd.c:617
call_rwsem_down_write_failed+0x13/0x20 arch/x86/lib/rwsem.S:105
__down_write arch/x86/include/asm/rwsem.h:126 [inline]
down_write+0x4f/0x90 kernel/locking/rwsem.c:56
grab_super+0x55/0x140 fs/super.c:373
sget_userns+0x2b4/0xc40 fs/super.c:504
sget+0xd1/0x110 fs/super.c:572
mount_bdev+0xcd/0x360 fs/super.c:1122
mount_fs+0x277/0x312 fs/super.c:1255
vfs_kern_mount.part.0+0xc7/0x4a0 fs/namespace.c:1056
vfs_kern_mount fs/namespace.c:1038 [inline]
do_new_mount fs/namespace.c:2573 [inline]
do_mount+0x3f6/0x26a0 fs/namespace.c:2903
SYSC_mount fs/namespace.c:3119 [inline]
SyS_mount+0xa8/0x120 fs/namespace.c:3096
do_syscall_64+0x19b/0x510 arch/x86/entry/common.c:292

Showing all locks held in the system:
1 lock held by khungtaskd/23:
#0: (tasklist_lock){.+.+}, at: [<00000000c159d2e7>]
debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4541
2 locks held by getty/1772:
#0: (&tty->ldisc_sem){++++}, at: [<0000000085bc67e6>]
tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
#1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000e4cc5d91>]
n_tty_read+0x1f7/0x1700 drivers/tty/n_tty.c:2156
2 locks held by syz-executor.1/28235:
#0: (&bdev->bd_fsfreeze_mutex){+.+.}, at: [<00000000d4595238>]
mount_bdev+0x71/0x360 fs/super.c:1116
#1: (&type->s_umount_key#34){++++}, at: [<0000000025a2e938>]
grab_super+0x55/0x140 fs/super.c:373

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

NMI backtrace for cpu 1
CPU: 1 PID: 23 Comm: khungtaskd Not tainted 4.14.129+ #11
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x10e lib/dump_stack.c:53
nmi_cpu_backtrace.cold+0x47/0x86 lib/nmi_backtrace.c:101
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 28230 Comm: syz-executor.0 Not tainted 4.14.129+ #11
task: 0000000020d7e9ff task.stack: 0000000005281c1b
RIP: 0010:__sanitizer_cov_trace_pc+0x4b/0x60 kernel/kcov.c:87
RSP: 0018:ffff88818cc1f858 EFLAGS: 00000287
RAX: 0000000000040000 RBX: ffff8881cf021a90 RCX: 000000000003ffff
RDX: ffffffff81b9ebc0 RSI: ffffc90001117000 RDI: ffffffff97748d40
RBP: ffffffff97748d40 R08: 0000000000000000 R09: 0000000000020025
R10: ffff8881a57c0858 R11: 0000000000000001 R12: 0000000000000000
R13: ffffffff97748d00 R14: 0000000000000001 R15: dffffc0000000000
FS: 00007f72c8f6b700(0000) GS:ffff8881dba00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001563978 CR3: 00000001885ce001 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
check_preemption_disabled+0x30/0x1f0 lib/smp_processor_id.c:16
rcu_dynticks_curr_cpu_in_eqs kernel/rcu/tree.c:360 [inline]
rcu_is_watching+0x11/0xb0 kernel/rcu/tree.c:1130
rcu_read_lock include/linux/rcupdate.h:630 [inline]
find_get_entry+0x31d/0x510 mm/filemap.c:1342
pagecache_get_page+0x44/0x790 mm/filemap.c:1458
find_get_page_flags include/linux/pagemap.h:283 [inline]
__find_get_block_slow fs/buffer.c:214 [inline]
__find_get_block+0x333/0x900 fs/buffer.c:1357
__getblk_slow fs/buffer.c:1100 [inline]
__getblk_gfp+0x18c/0x710 fs/buffer.c:1383
Code: 11 00 00 83 fa 01 74 01 c3 48 c7 c2 00 00 00 81 48 81 ea 00 00 80 95
48 03 14 24 48 8b b0 b0 11 00 00 8b 80 ac 11 00 00 48 8b 0e <48> 83 c1 01
48 39 c8 76 d4 48 89 14 ce 48 89 0e c3 0f 1f 40 00


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.