syzbot


possible deadlock in seq_read (2)

Status: auto-obsoleted due to no activity on 2022/09/01 16:45
Reported-by: syzbot+eb2fac11ac7c4db9bf49@syzkaller.appspotmail.com
First crash: 720d, last: 720d
Similar bugs (7)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 possible deadlock in seq_read 144 1087d 1761d 0/1 auto-closed as invalid on 2021/08/31 02:48
android-44 possible deadlock in seq_read C 632 1603d 1839d 0/2 public: reported C repro on 2019/04/11 08:44
android-49 possible deadlock in seq_read C 56124 1602d 1839d 1/3 public: reported C repro on 2019/04/12 00:00
linux-4.19 possible deadlock in seq_read C error 290 453d 1723d 0/1 upstream: reported C repro on 2019/08/05 16:40
upstream possible deadlock in seq_read (2) overlayfs C done error 95 1300d 1836d 0/26 auto-obsoleted due to no activity on 2022/09/24 20:28
upstream possible deadlock in seq_read fs C 19074 1846d 2335d 12/26 fixed on 2019/04/12 08:05
android-414 possible deadlock in seq_read C 1737 1693d 1840d 0/1 public: reported C repro on 2019/04/11 00:00

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
4.14.277-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.1/13919 is trying to acquire lock:
 (&p->lock){+.+.}, at: [<ffffffff818ef6ea>] seq_read+0xba/0x1180 fs/seq_file.c:168

but task is already holding lock:
 (sb_writers#3){.+.+}, at: [<ffffffff8186e50f>] file_start_write include/linux/fs.h:2714 [inline]
 (sb_writers#3){.+.+}, at: [<ffffffff8186e50f>] do_sendfile+0x84f/0xb30 fs/read_write.c:1440

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (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:1551 [inline]
       mnt_want_write+0x3a/0xb0 fs/namespace.c:386
       ovl_do_remove+0x67/0xb90 fs/overlayfs/dir.c:759
       vfs_rmdir.part.0+0x144/0x390 fs/namei.c:3908
       vfs_rmdir fs/namei.c:3893 [inline]
       do_rmdir+0x334/0x3c0 fs/namei.c:3968
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #2 (&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

-> #1 (&sig->cred_guard_mutex){+.+.}:
       __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:2738 [inline]
       proc_tgid_io_accounting+0x1b9/0x7a0 fs/proc/base.c:2787
       proc_single_show+0xe7/0x150 fs/proc/base.c:761
       seq_read+0x4e4/0x1180 fs/seq_file.c:240
       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
       do_preadv fs/read_write.c:1065 [inline]
       SYSC_preadv fs/read_write.c:1115 [inline]
       SyS_preadv+0x15a/0x200 fs/read_write.c:1110
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x46/0xbb

-> #0 (&p->lock){+.+.}:
       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
       seq_read+0xba/0x1180 fs/seq_file.c:168
       proc_reg_read+0xee/0x1a0 fs/proc/inode.c:217
       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:
  &p->lock --> &ovl_i_mutex_dir_key[depth] --> sb_writers#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#3);
                               lock(&ovl_i_mutex_dir_key[depth]);
                               lock(sb_writers#3);
  lock(&p->lock);

 *** DEADLOCK ***

1 lock held by syz-executor.1/13919:
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff8186e50f>] file_start_write include/linux/fs.h:2714 [inline]
 #0:  (sb_writers#3){.+.+}, at: [<ffffffff8186e50f>] do_sendfile+0x84f/0xb30 fs/read_write.c:1440

stack backtrace:
CPU: 0 PID: 13919 Comm: syz-executor.1 Not tainted 4.14.277-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
 seq_read+0xba/0x1180 fs/seq_file.c:168
 proc_reg_read+0xee/0x1a0 fs/proc/inode.c:217
 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: 0033:0x7f0d0cbb80e9
RSP: 002b:00007f0d0b52d168 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f0d0cccaf60 RCX: 00007f0d0cbb80e9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000003
RBP: 00007f0d0cc1208d R08: 0000000000000000 R09: 0000000000000000
R10: 4000000000010046 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe42448e6f R14: 00007f0d0b52d300 R15: 0000000000022000
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: missing 'lowerdir'
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "obj_role=[(" or missing value
gfs2: gfs2 mount does not exist
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: missing 'lowerdir'
kauditd_printk_skb: 3 callbacks suppressed
audit: type=1800 audit(1651682687.775:36): pid=14001 uid=0 auid=4294967295 ses=4294967295 op="collect_data" cause="failed(directio)" comm="syz-executor.0" name="bus" dev="sda1" ino=14307 res=0
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "obj_role=[(" or missing value
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: missing 'lowerdir'
overlayfs: missing 'lowerdir'
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "obj_role=[(" or missing value
overlayfs: unrecognized mount option "obj_role=[(" or missing value
gfs2: gfs2 mount does not exist
overlayfs: fs on 'file0' does not support file handles, falling back to index=off.
overlayfs: missing 'lowerdir'
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
overlayfs: unrecognized mount option "obj_role=[(" or missing value
audit: type=1800 audit(1651682688.675:37): pid=14084 uid=0 auid=4294967295 ses=4294967295 op="collect_data" cause="failed(directio)" comm="syz-executor.0" name="bus" dev="sda1" ino=14295 res=0
gfs2: gfs2 mount does not exist
EXT4-fs (loop5): Unrecognized mount option "Z" or missing value
audit: type=1800 audit(1651682688.815:38): pid=14108 uid=0 auid=4294967295 ses=4294967295 op="collect_data" cause="failed(directio)" comm="syz-executor.0" name="bus" dev="sda1" ino=14309 res=0
EXT4-fs (loop5): Unrecognized mount option "Z" or missing value
EXT4-fs (loop5): Unrecognized mount option "Z" or missing value
EXT4-fs (loop0): Unrecognized mount option "Z" or missing value
print_req_error: I/O error, dev loop0, sector 0
Zero length message leads to an empty skb
bridge0: port 3(team0) entered blocking state
bridge0: port 3(team0) entered disabled state
device team0 entered promiscuous mode
device team_slave_0 entered promiscuous mode
device team_slave_1 entered promiscuous mode
device ipvlan1 entered promiscuous mode
bridge0: port 3(team0) entered blocking state
bridge0: port 3(team0) entered forwarding state
bridge0: port 3(team0) entered blocking state
bridge0: port 3(team0) entered disabled state
device team0 entered promiscuous mode
device team_slave_0 entered promiscuous mode
device team_slave_1 entered promiscuous mode
bridge0: port 3(team0) entered blocking state
bridge0: port 3(team0) entered forwarding state
print_req_error: I/O error, dev loop0, sector 0
unregister_netdevice: waiting for ip6gre0 to become free. Usage count = -1

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2022/05/04 16:44 linux-4.14.y e3a56aaade89 dc9e5259 .config console log report info ci2-linux-4-14 possible deadlock in seq_read
* Struck through repros no longer work on HEAD.