syzbot

 sign-in | mailing list | source | docs
🐞 Open [717]
🐞 Fixed [181]
🐞 Invalid [640]
≡ Crashes
Kernel Health Bugs/Month Bug Lifetimes Fuzzing
💬 Send us feedback

possible deadlock in proc_tgid_io_accounting

Status: upstream: reported C repro on 2020/08/03 19:18
Reported-by: syzbot+1a6d6e76ff4c5f8008e3@syzkaller.appspotmail.com
First crash: 1967d, last: 1356d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in proc_tgid_io_accounting fs 4 9 2091d 2149d 0/29 auto-closed as invalid on 2020/07/30 02:14
linux-4.19 possible deadlock in proc_tgid_io_accounting 4 208 1153d 1966d 0/1 auto-obsoleted due to no activity on 2023/02/23 02:05
upstream possible deadlock in proc_tgid_io_accounting (2) fs 4 1 1932d 1928d 0/29 auto-closed as invalid on 2021/01/04 23:12
linux-4.19 possible deadlock in proc_tgid_io_accounting (2) 4 2 1025d 1030d 0/1 upstream: reported on 2023/02/26 17:26
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2023/02/26 20:32 9m retest repro linux-4.14.y report log
2022/11/08 00:30 10m retest repro linux-4.14.y report log
▶ ▼ Fix bisection attempts (12)
Created Duration User Patch Repo Result
2022/05/06 06:44 11m bisect fix linux-4.14.y error job log
2022/04/06 06:22 21m bisect fix linux-4.14.y OK (0) job log log
2022/03/07 05:52 20m bisect fix linux-4.14.y OK (0) job log log
2022/02/05 05:22 30m bisect fix linux-4.14.y OK (0) job log log
2022/01/06 04:52 29m bisect fix linux-4.14.y OK (0) job log log
2021/12/07 04:26 25m bisect fix linux-4.14.y OK (0) job log log
2021/11/07 04:02 23m bisect fix linux-4.14.y OK (0) job log log
2021/10/08 03:39 22m bisect fix linux-4.14.y OK (0) job log log
2021/09/08 03:11 28m bisect fix linux-4.14.y OK (0) job log log
2021/08/09 02:45 25m bisect fix linux-4.14.y OK (0) job log log
2021/07/10 02:24 21m bisect fix linux-4.14.y OK (0) job log log
2021/06/10 02:04 19m bisect fix linux-4.14.y OK (0) job log log

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
4.14.232-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor612/7953 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.}, at: [<ffffffff81a03109>] do_io_accounting fs/proc/base.c:2725 [inline]
 (&sig->cred_guard_mutex){+.+.}, at: [<ffffffff81a03109>] proc_tgid_io_accounting+0x1b9/0x7a0 fs/proc/base.c:2774

but task is already holding lock:
 (&p->lock){+.+.}, at: [<ffffffff818e979a>] seq_read+0xba/0x1120 fs/seq_file.c:165

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->lock){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
       seq_read+0xba/0x1120 fs/seq_file.c:165
       do_loop_readv_writev fs/read_write.c:695 [inline]
       do_loop_readv_writev fs/read_write.c:682 [inline]
       do_iter_read+0x3eb/0x5b0 fs/read_write.c:919
       vfs_readv+0xc8/0x120 fs/read_write.c:981
       kernel_readv fs/splice.c:361 [inline]
       default_file_splice_read+0x418/0x910 fs/splice.c:416
       do_splice_to+0xfb/0x140 fs/splice.c:880
       splice_direct_to_actor+0x207/0x730 fs/splice.c:952
       do_splice_direct+0x164/0x210 fs/splice.c:1061
       do_sendfile+0x47f/0xb30 fs/read_write.c:1441
       SYSC_sendfile64 fs/read_write.c:1502 [inline]
       SyS_sendfile64+0xff/0x110 fs/read_write.c:1488
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #2 (sb_writers#3){.+.+}:
       percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline]
       percpu_down_read include/linux/percpu-rwsem.h:59 [inline]
       __sb_start_write+0x64/0x260 fs/super.c:1342
       sb_start_write include/linux/fs.h:1549 [inline]
       mnt_want_write+0x3a/0xb0 fs/namespace.c:386
       ovl_create_object+0x75/0x1d0 fs/overlayfs/dir.c:538
       lookup_open+0x77a/0x1750 fs/namei.c:3241
       do_last fs/namei.c:3334 [inline]
       path_openat+0xe08/0x2970 fs/namei.c:3569
       do_filp_open+0x179/0x3c0 fs/namei.c:3603
       do_sys_open+0x296/0x410 fs/open.c:1081
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #1 (&ovl_i_mutex_dir_key[depth]){++++}:
       down_read+0x36/0x80 kernel/locking/rwsem.c:24
       inode_lock_shared include/linux/fs.h:729 [inline]
       do_last fs/namei.c:3333 [inline]
       path_openat+0x149b/0x2970 fs/namei.c:3569
       do_filp_open+0x179/0x3c0 fs/namei.c:3603
       do_open_execat+0xd3/0x450 fs/exec.c:849
       do_execveat_common+0x711/0x1f30 fs/exec.c:1755
       do_execve fs/exec.c:1860 [inline]
       SYSC_execve fs/exec.c:1941 [inline]
       SyS_execve+0x3b/0x50 fs/exec.c:1936
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #0 (&sig->cred_guard_mutex){+.+.}:
       lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
       do_io_accounting fs/proc/base.c:2725 [inline]
       proc_tgid_io_accounting+0x1b9/0x7a0 fs/proc/base.c:2774
       proc_single_show+0xe7/0x150 fs/proc/base.c:761
       seq_read+0x4cf/0x1120 fs/seq_file.c:237
       do_loop_readv_writev fs/read_write.c:695 [inline]
       do_loop_readv_writev fs/read_write.c:682 [inline]
       do_iter_read+0x3eb/0x5b0 fs/read_write.c:919
       vfs_readv+0xc8/0x120 fs/read_write.c:981
       kernel_readv fs/splice.c:361 [inline]
       default_file_splice_read+0x418/0x910 fs/splice.c:416
       do_splice_to+0xfb/0x140 fs/splice.c:880
       splice_direct_to_actor+0x207/0x730 fs/splice.c:952
       do_splice_direct+0x164/0x210 fs/splice.c:1061
       do_sendfile+0x47f/0xb30 fs/read_write.c:1441
       SYSC_sendfile64 fs/read_write.c:1502 [inline]
       SyS_sendfile64+0xff/0x110 fs/read_write.c:1488
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x46/0xbb

other info that might help us debug this:

Chain exists of:
  &sig->cred_guard_mutex --> sb_writers#3 --> &p->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&p->lock);
                               lock(sb_writers#3);
                               lock(&p->lock);
  lock(&sig->cred_guard_mutex);

 *** DEADLOCK ***

2 locks held by syz-executor612/7953:
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff8186b31f>] file_start_write include/linux/fs.h:2712 [inline]
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff8186b31f>] do_sendfile+0x84f/0xb30 fs/read_write.c:1440
 #1:  (&p->lock){+.+.}, at: [<ffffffff818e979a>] seq_read+0xba/0x1120 fs/seq_file.c:165

stack backtrace:
CPU: 1 PID: 7953 Comm: syz-executor612 Not tainted 4.14.232-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
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1258
 check_prev_add kernel/locking/lockdep.c:1905 [inline]
 check_prevs_add kernel/locking/lockdep.c:2022 [inline]
 validate_chain kernel/locking/lockdep.c:2464 [inline]
 __lock_acquire+0x2e0e/0x3f20 kernel/locking/lockdep.c:3491
 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
 __mutex_lock_common kernel/locking/mutex.c:756 [inline]
 __mutex_lock+0xc4/0x1310 kernel/locking/mutex.c:893
 do_io_accounting fs/proc/base.c:2725 [inline]
 proc_tgid_io_accounting+0x1b9/0x7a0 fs/proc/base.c:2774
 proc_single_show+0xe7/0x150 fs/proc/base.c:761
 seq_read+0x4cf/0x1120 fs/seq_file.c:237
 do_loop_readv_writev fs/read_write.c:695 [inline]
 do_loop_readv_writev fs/read_write.c:682 [inline]
 do_iter_read+0x3eb/0x5b0 fs/read_write.c:919
 vfs_readv+0xc8/0x120 fs/read_write.c:981
 kernel_readv fs/splice.c:361 [inline]
 default_file_splice_read+0x418/0x910 fs/splice.c:416
 do_splice_to+0xfb/0x140 fs/splice.c:880
 splice_direct_to_actor+0x207/0x730 fs/splice.c:952
 do_splice_direct+0x164/0x210 fs/splice.c:1061
 do_sendfile+0x47f/0xb30 fs/read_write.c:1441
 SYSC_sendfile64 fs/read_write.c:1502 [inline]
 SyS_sendfile64+0xff/0x110 fs/read_write.c:1488
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x43f239
RSP: 002b:00007fff55c1dd68 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043f239
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2021/05/11 02:04 linux-4.14.y 7d7d1c0ab3eb ca873091 .config console log report syz C ci2-linux-4-14 possible deadlock in proc_tgid_io_accounting
2021/05/09 15:25 linux-4.14.y 7d7d1c0ab3eb bc5434be .config console log report info ci2-linux-4-14 possible deadlock in proc_tgid_io_accounting
2021/05/06 20:39 linux-4.14.y 7d7d1c0ab3eb 06585184 .config console log report info ci2-linux-4-14 possible deadlock in proc_tgid_io_accounting
2021/05/01 15:55 linux-4.14.y 7d7d1c0ab3eb 77e2b668 .config console log report info ci2-linux-4-14 possible deadlock in proc_tgid_io_accounting
2021/02/28 13:58 linux-4.14.y 3242aa3a635c 4c37c133 .config console log report info ci2-linux-4-14 possible deadlock in proc_tgid_io_accounting
2020/11/21 22:14 linux-4.14.y 8961076ed318 c7ec2d19 .config console log report info ci2-linux-4-14
2020/08/30 00:22 linux-4.14.y d7e78d08fa77 d5a3ae1f .config console log report ci2-linux-4-14
2020/08/10 11:46 linux-4.14.y 14b58326976d 7adc7b65 .config console log report ci2-linux-4-14
2020/08/03 19:17 linux-4.14.y 7f2c5eb458b8 96dd3623 .config console log report ci2-linux-4-14
* Struck through repros no longer work on HEAD.