Message-ID: <000000000000cec1940570940acf@google.com>
Date:   Mon, 09 Jul 2018 10:07:02 -0700
From:   syzbot <syzbot+9d0373cdac2be4979750@...kaller.appspotmail.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: INFO: task hung in vfs_removexattr

Hello,

syzbot found the following crash on:

HEAD commit:    1e4b044d2251 Linux 4.18-rc4
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14dc81b2400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=25856fac4e580aa7
dashboard link: https://syzkaller.appspot.com/bug?extid=9d0373cdac2be4979750
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+9d0373cdac2be4979750@...kaller.appspotmail.com

netlink: 16 bytes leftover after parsing attributes in process  
`syz-executor0'.
netlink: 16 bytes leftover after parsing attributes in process  
`syz-executor0'.
INFO: task syz-executor5:14548 blocked for more than 140 seconds.
       Not tainted 4.18.0-rc4+ #138
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D24752 14548   4547 0x00000004
Call Trace:
  context_switch kernel/sched/core.c:2853 [inline]
  __schedule+0x87c/0x1ed0 kernel/sched/core.c:3501
  schedule+0xfb/0x450 kernel/sched/core.c:3545
  __rwsem_down_write_failed_common+0x95d/0x1630  
kernel/locking/rwsem-xadd.c:566
  rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:595
  call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117
  __down_write arch/x86/include/asm/rwsem.h:142 [inline]
  down_write+0xaa/0x130 kernel/locking/rwsem.c:72
  inode_lock include/linux/fs.h:715 [inline]
  vfs_removexattr+0x82/0x1c0 fs/xattr.c:391
  removexattr+0xd3/0x130 fs/xattr.c:691
  path_removexattr+0x1b9/0x210 fs/xattr.c:705
  __do_sys_removexattr fs/xattr.c:719 [inline]
  __se_sys_removexattr fs/xattr.c:716 [inline]
  __x64_sys_removexattr+0x59/0x80 fs/xattr.c:716
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455e29
Code: cc 64 48 8b 0c 25 f8 ff ff ff 48 3b 61 10 0f 86 ab 04 00 00 48 83 ec  
58 48 89 6c 24 50 48 8d 6c 24 50 48 8b 44 24 60 c6 00 00 <48> 8b 4c 24 68  
48 89 ca 48 89 50 08 48 8b 59 20 48 01 da 31 db 31
RSP: 002b:00007f4465180c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000c5
RAX: ffffffffffffffda RBX: 00007f44651816d4 RCX: 0000000000455e29
RDX: 0000000000000000 RSI: 0000000020000400 RDI: 0000000020000380
RBP: 000000000072bf48 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004bbfeb R14: 00000000004d1108 R15: 0000000000000001

Showing all locks held in the system:
1 lock held by khungtaskd/901:
  #0: 00000000ebf24c36 (rcu_read_lock){....}, at:  
debug_show_all_locks+0xd0/0x428 kernel/locking/lockdep.c:4461
1 lock held by rsyslogd/4405:
2 locks held by getty/4495:
  #0: 00000000692a9d2f (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 0000000072fe5412 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4496:
  #0: 000000002b623882 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 0000000056c15f7c (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4497:
  #0: 000000002c1f858b (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 0000000048aba06b (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4498:
  #0: 00000000da02f89a (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 000000004a06c40f (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4499:
  #0: 0000000017508207 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 00000000a4b24877 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4500:
  #0: 0000000079a247d3 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 000000009bcfd45d (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by getty/4501:
  #0: 00000000e73958a9 (&tty->ldisc_sem){++++}, at:  
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
  #1: 000000007d96a629 (&ldata->atomic_read_lock){+.+.}, at:  
n_tty_read+0x335/0x1ce0 drivers/tty/n_tty.c:2140
2 locks held by syz-executor5/14500:
  #0: 00000000ba1ef7f9 (sb_writers#19){.+.+}, at: sb_start_write  
include/linux/fs.h:1554 [inline]
  #0: 00000000ba1ef7f9 (sb_writers#19){.+.+}, at: mnt_want_write+0x3f/0xc0  
fs/namespace.c:386
  #1: 00000000e4cbde96 (&sb->s_type->i_mutex_key#25){++++}, at: inode_lock  
include/linux/fs.h:715 [inline]
  #1: 00000000e4cbde96 (&sb->s_type->i_mutex_key#25){++++}, at:  
vfs_removexattr+0x82/0x1c0 fs/xattr.c:391
2 locks held by syz-executor5/14548:
  #0: 00000000ba1ef7f9 (sb_writers#19){.+.+}, at: sb_start_write  
include/linux/fs.h:1554 [inline]
  #0: 00000000ba1ef7f9 (sb_writers#19){.+.+}, at: mnt_want_write+0x3f/0xc0  
fs/namespace.c:386
  #1: 00000000e4cbde96 (&sb->s_type->i_mutex_key#25){++++}, at: inode_lock  
include/linux/fs.h:715 [inline]
  #1: 00000000e4cbde96 (&sb->s_type->i_mutex_key#25){++++}, at:  
vfs_removexattr+0x82/0x1c0 fs/xattr.c:391

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

NMI backtrace for cpu 0
CPU: 0 PID: 901 Comm: khungtaskd Not tainted 4.18.0-rc4+ #138
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.4+0x19/0xce lib/nmi_backtrace.c:103
  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:138 [inline]
  check_hung_uninterruptible_tasks kernel/hung_task.c:196 [inline]
  watchdog+0x9c4/0xf80 kernel/hung_task.c:252
  kthread+0x345/0x410 kernel/kthread.c:246
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10  
arch/x86/include/asm/irqflags.h:54


---
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