syzbot


INFO: task hung in vfs_unlink (2)

Status: auto-closed as invalid on 2021/08/17 05:41
Reported-by: syzbot+5c92d80da57117e2b570@syzkaller.appspotmail.com
First crash: 431d, last: 431d
similar bugs (5):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 INFO: task hung in vfs_unlink 8 676d 918d 0/1 auto-closed as invalid on 2020/12/15 00:37
linux-4.19 INFO: task hung in vfs_unlink (2) 2 686d 747d 0/1 auto-closed as invalid on 2020/12/05 18:54
upstream INFO: task hung in vfs_unlink 32 698d 975d 0/22 auto-closed as invalid on 2020/11/23 01:14
linux-4.19 INFO: task hung in vfs_unlink 6 877d 1001d 0/1 auto-closed as invalid on 2020/05/28 17:30
linux-4.19 INFO: task hung in vfs_unlink (3) 1 324d 324d 0/1 auto-closed as invalid on 2021/12/01 23:35

Sample crash report:
INFO: task syz-executor.4:10777 blocked for more than 140 seconds.
      Not tainted 4.14.231-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D25912 10777      1 0x00000004
Call Trace:
 context_switch kernel/sched/core.c:2808 [inline]
 __schedule+0x88b/0x1de0 kernel/sched/core.c:3384
 schedule+0x8d/0x1b0 kernel/sched/core.c:3428
 __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:588 [inline]
 rwsem_down_write_failed+0x343/0x6d0 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
 inode_lock include/linux/fs.h:719 [inline]
 vfs_unlink+0xc0/0x470 fs/namei.c:4018
 do_unlinkat+0x30c/0x5c0 fs/namei.c:4092
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x465d97
RSP: 002b:00007ffc4a67f038 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000465d97
RDX: 00007ffc4a67f070 RSI: 00007ffc4a67f070 RDI: 00007ffc4a67f100
RBP: 00007ffc4a67f100 R08: 0000000000000001 R09: 00007ffc4a67eed0
R10: 00000000025148c3 R11: 0000000000000206 R12: 00000000004bebb2
R13: 00007ffc4a6801d0 R14: 0000000002514810 R15: 00007ffc4a680210

Showing all locks held in the system:
1 lock held by khungtaskd/1533:
 #0:  (tasklist_lock){.+.+}, at: [<ffffffff8700a357>] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548
1 lock held by in:imklog/7767:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff818d37fb>] __fdget_pos+0x1fb/0x2b0 fs/file.c:769
3 locks held by syz-executor.4/10777:
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff818dc65a>] sb_start_write include/linux/fs.h:1549 [inline]
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff818dc65a>] mnt_want_write+0x3a/0xb0 fs/namespace.c:386
 #1:  (&type->i_mutex_dir_key#3/1){+.+.}, at: [<ffffffff818a4bc1>] inode_lock_nested include/linux/fs.h:754 [inline]
 #1:  (&type->i_mutex_dir_key#3/1){+.+.}, at: [<ffffffff818a4bc1>] do_unlinkat+0x201/0x5c0 fs/namei.c:4078
 #2:  (&sb->s_type->i_mutex_key#10){++++}, at: [<ffffffff818963b0>] inode_lock include/linux/fs.h:719 [inline]
 #2:  (&sb->s_type->i_mutex_key#10){++++}, at: [<ffffffff818963b0>] vfs_unlink+0xc0/0x470 fs/namei.c:4018
3 locks held by syz-executor.4/338:
 #0:  (&f->f_pos_lock){+.+.}, at: [<ffffffff818d37fb>] __fdget_pos+0x1fb/0x2b0 fs/file.c:769
 #1:  (sb_writers#3){.+.+}, at: [<ffffffff8186d6c8>] file_start_write include/linux/fs.h:2712 [inline]
 #1:  (sb_writers#3){.+.+}, at: [<ffffffff8186d6c8>] vfs_write+0x3d8/0x4d0 fs/read_write.c:543
 #2:  (&sb->s_type->i_mutex_key#10){++++}, at: [<ffffffff81b738cc>] inode_trylock include/linux/fs.h:739 [inline]
 #2:  (&sb->s_type->i_mutex_key#10){++++}, at: [<ffffffff81b738cc>] ext4_file_write_iter+0x1cc/0xd20 fs/ext4/file.c:236

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

NMI backtrace for cpu 1
CPU: 1 PID: 1533 Comm: khungtaskd Not tainted 4.14.231-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x13a/0x180 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
 watchdog+0x5b9/0xb40 kernel/hung_task.c:274
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4623 Comm: systemd-journal Not tainted 4.14.231-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880a1188100 task.stack: ffff8880a1190000
RIP: 0010:__orc_find+0x20/0xf0 arch/x86/kernel/unwind_orc.c:46
RSP: 0018:ffff8880a1197a20 EFLAGS: 00000283
RAX: 0000000000000010 RBX: 1ffff11014232f54 RCX: ffffffff817ebbea
RDX: 0000000000000010 RSI: ffffffff8a7217a4 RDI: ffffffff8a19042c
RBP: 0000000000000001 R08: ffffffff8a7217a4 R09: ffffffff8a721804
R10: 000000000001e806 R11: 0000000000066071 R12: ffffffff8a190468
R13: ffff8880a1197b60 R14: ffff8880a1197b78 R15: ffff8880a1197b28
FS:  00007f62b1a928c0(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f62af130018 CR3: 00000000a1201000 CR4: 00000000001426f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 orc_find arch/x86/kernel/unwind_orc.c:118 [inline]
 unwind_next_frame+0x59a/0x17d0 arch/x86/kernel/unwind_orc.c:348
 __save_stack_trace+0x90/0x160 arch/x86/kernel/stacktrace.c:44
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
 prepare_creds+0x39/0x490 kernel/cred.c:255
 SYSC_faccessat fs/open.c:365 [inline]
 SyS_faccessat+0x7b/0x680 fs/open.c:353
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7f62b0d4d9c7
RSP: 002b:00007fff53118558 EFLAGS: 00000246 ORIG_RAX: 0000000000000015
RAX: ffffffffffffffda RBX: 00007fff5311b580 RCX: 00007f62b0d4d9c7
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00005581b10da9a3
RBP: 00007fff531186a0 R08: 00005581b10d03e5 R09: 0000000000000018
R10: 0000000000000069 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00005581b2bc38a0 R15: 00007fff53118b90
Code: 90 90 90 90 90 90 90 90 90 90 90 41 57 89 d0 41 56 41 55 41 54 4c 8d 64 87 fc 55 53 48 83 ec 10 85 d2 0f 84 95 00 00 00 4c 39 e7 <49> 89 fd 0f 87 9a 00 00 00 49 bf 00 00 00 00 00 fc ff df 49 89 

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2021/04/19 05:41 linux-4.14.y cf256fbcbe34 7e2b734b .config log report info INFO: task hung in vfs_unlink