syzbot


possible deadlock in proc_pid_attr_write

Status: auto-closed as invalid on 2020/05/23 15:46
Reported-by: syzbot+fb469ad2c0cb8f47e8b2@syzkaller.appspotmail.com
First crash: 971d, last: 882d
similar bugs (6):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-414 possible deadlock in proc_pid_attr_write C 203 1185d 1170d 0/1 public: reported C repro on 2019/04/11 00:00
upstream possible deadlock in proc_pid_attr_write (2) 1 860d 856d 0/22 auto-closed as invalid on 2020/04/15 17:32
linux-4.19 possible deadlock in proc_pid_attr_write 1 644d 644d 0/1 auto-closed as invalid on 2021/01/16 05:53
upstream possible deadlock in proc_pid_attr_write C 281 1184d 1658d 0/22 closed as dup on 2017/12/12 22:00
linux-4.14 possible deadlock in proc_pid_attr_write (2) 1 427d 427d 0/1 auto-closed as invalid on 2021/08/21 09:25
linux-4.19 possible deadlock in proc_pid_attr_write (2) 1 272d 272d 0/1 auto-closed as invalid on 2022/01/23 20:06

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
4.14.167-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.5/26909 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.}, at: [<ffffffff81a9a753>] proc_pid_attr_write+0x163/0x290 fs/proc/base.c:2585

but task is already holding lock:
 (&pipe->mutex/1){+.+.}, at: [<ffffffff81912a43>] pipe_lock_nested fs/pipe.c:67 [inline]
 (&pipe->mutex/1){+.+.}, at: [<ffffffff81912a43>] pipe_lock+0x63/0x80 fs/pipe.c:75

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&pipe->mutex/1){+.+.}:
       lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
       mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
       pipe_lock_nested fs/pipe.c:67 [inline]
       pipe_lock+0x63/0x80 fs/pipe.c:75
       iter_file_splice_write+0x15e/0xad0 fs/splice.c:699
       do_splice_from fs/splice.c:851 [inline]
       do_splice fs/splice.c:1147 [inline]
       SYSC_splice fs/splice.c:1402 [inline]
       SyS_splice+0xd92/0x1430 fs/splice.c:1382
       do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #2 (sb_writers#4){.+.+}:
       lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
       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+0x1ae/0x2f0 fs/super.c:1363
       sb_start_write include/linux/fs.h:1548 [inline]
       mnt_want_write+0x3f/0xb0 fs/namespace.c:386
       ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:25
       ovl_xattr_set+0x4f/0x270 fs/overlayfs/inode.c:214
       ovl_posix_acl_xattr_set+0x3f9/0x830 fs/overlayfs/super.c:762
       __vfs_setxattr+0xd8/0x130 fs/xattr.c:150
       __vfs_setxattr_noperm+0x102/0x3c0 fs/xattr.c:181
       vfs_setxattr+0xc5/0xf0 fs/xattr.c:224
       setxattr+0x1de/0x350 fs/xattr.c:453
       path_setxattr+0x11f/0x140 fs/xattr.c:472
       SYSC_lsetxattr fs/xattr.c:494 [inline]
       SyS_lsetxattr+0x38/0x50 fs/xattr.c:490
       do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #1 (&ovl_i_mutex_dir_key[depth]){++++}:
       lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
       down_read+0x3b/0xb0 kernel/locking/rwsem.c:24
       inode_lock_shared include/linux/fs.h:728 [inline]
       do_last fs/namei.c:3330 [inline]
       path_openat+0x191c/0x3f70 fs/namei.c:3566
       do_filp_open+0x18e/0x250 fs/namei.c:3600
       do_open_execat+0xe7/0x4a0 fs/exec.c:849
       do_execveat_common.isra.0+0x6d5/0x1dd0 fs/exec.c:1740
       do_execve fs/exec.c:1847 [inline]
       SYSC_execve fs/exec.c:1928 [inline]
       SyS_execve+0x39/0x50 fs/exec.c:1923
       do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 (&sig->cred_guard_mutex){+.+.}:
       check_prev_add kernel/locking/lockdep.c:1901 [inline]
       check_prevs_add kernel/locking/lockdep.c:2018 [inline]
       validate_chain kernel/locking/lockdep.c:2460 [inline]
       __lock_acquire+0x2cb3/0x4620 kernel/locking/lockdep.c:3487
       lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
       mutex_lock_interruptible_nested+0x16/0x20 kernel/locking/mutex.c:930
       proc_pid_attr_write+0x163/0x290 fs/proc/base.c:2585
       __vfs_write+0x105/0x6b0 fs/read_write.c:480
       __kernel_write+0xfc/0x370 fs/read_write.c:501
       write_pipe_buf+0x148/0x1c0 fs/splice.c:797
       splice_from_pipe_feed fs/splice.c:502 [inline]
       __splice_from_pipe+0x348/0x780 fs/splice.c:626
       splice_from_pipe+0xf0/0x150 fs/splice.c:661
       default_file_splice_write+0x3c/0x80 fs/splice.c:809
       do_splice_from fs/splice.c:851 [inline]
       do_splice fs/splice.c:1147 [inline]
       SYSC_splice fs/splice.c:1402 [inline]
       SyS_splice+0xd92/0x1430 fs/splice.c:1382
       do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

other info that might help us debug this:

Chain exists of:
  &sig->cred_guard_mutex --> sb_writers#4 --> &pipe->mutex/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pipe->mutex/1);
                               lock(sb_writers#4);
                               lock(&pipe->mutex/1);
  lock(&sig->cred_guard_mutex);

 *** DEADLOCK ***

2 locks held by syz-executor.5/26909:
 #0:  (sb_writers#7){.+.+}, at: [<ffffffff819ae26a>] file_start_write include/linux/fs.h:2707 [inline]
 #0:  (sb_writers#7){.+.+}, at: [<ffffffff819ae26a>] do_splice fs/splice.c:1146 [inline]
 #0:  (sb_writers#7){.+.+}, at: [<ffffffff819ae26a>] SYSC_splice fs/splice.c:1402 [inline]
 #0:  (sb_writers#7){.+.+}, at: [<ffffffff819ae26a>] SyS_splice+0xf3a/0x1430 fs/splice.c:1382
 #1:  (&pipe->mutex/1){+.+.}, at: [<ffffffff81912a43>] pipe_lock_nested fs/pipe.c:67 [inline]
 #1:  (&pipe->mutex/1){+.+.}, at: [<ffffffff81912a43>] pipe_lock+0x63/0x80 fs/pipe.c:75

stack backtrace:
CPU: 0 PID: 26909 Comm: syz-executor.5 Not tainted 4.14.167-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+0x142/0x197 lib/dump_stack.c:58
 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1258
 check_prev_add kernel/locking/lockdep.c:1901 [inline]
 check_prevs_add kernel/locking/lockdep.c:2018 [inline]
 validate_chain kernel/locking/lockdep.c:2460 [inline]
 __lock_acquire+0x2cb3/0x4620 kernel/locking/lockdep.c:3487
 lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994
 __mutex_lock_common kernel/locking/mutex.c:756 [inline]
 __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893
 mutex_lock_interruptible_nested+0x16/0x20 kernel/locking/mutex.c:930
 proc_pid_attr_write+0x163/0x290 fs/proc/base.c:2585
 __vfs_write+0x105/0x6b0 fs/read_write.c:480
 __kernel_write+0xfc/0x370 fs/read_write.c:501
 write_pipe_buf+0x148/0x1c0 fs/splice.c:797
 splice_from_pipe_feed fs/splice.c:502 [inline]
 __splice_from_pipe+0x348/0x780 fs/splice.c:626
 splice_from_pipe+0xf0/0x150 fs/splice.c:661
 default_file_splice_write+0x3c/0x80 fs/splice.c:809
 do_splice_from fs/splice.c:851 [inline]
 do_splice fs/splice.c:1147 [inline]
 SYSC_splice fs/splice.c:1402 [inline]
 SyS_splice+0xd92/0x1430 fs/splice.c:1382
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45b349
RSP: 002b:00007f8194ae4c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f8194ae56d4 RCX: 000000000045b349
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000080000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000b3e R14: 00000000004ccc7e R15: 000000000075bf2c
selinux_nlmsg_perm: 235 callbacks suppressed
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27006 comm=syz-executor.5
x_tables: ip_tables: rpfilter match: used from hooks INPUT, but only valid from PREROUTING
x_tables: ip_tables: rpfilter match: used from hooks INPUT, but only valid from PREROUTING
audit: type=1804 audit(1579880755.027:283): pid=27197 uid=0 auid=4294967295 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 op="invalid_pcr" cause="ToMToU" comm="syz-executor.3" name="/root/syzkaller-testdir926441775/syzkaller.5vQr5P/2226/file0" dev="sda1" ino=16617 res=1
audit: type=1400 audit(1579880756.757:284): avc:  denied  { getattr } for  pid=27285 comm="syz-executor.2" path="socket:[383848]" dev="sockfs" ino=383848 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
selinux_nlmsg_perm: 352 callbacks suppressed
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
caif:caif_disconnect_client(): nothing to disconnect
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
caif:caif_disconnect_client(): nothing to disconnect
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=0 sclass=netlink_tcpdiag_socket pig=27350 comm=syz-executor.5
overlayfs: unrecognized mount option "metacopy=off" or missing value
audit: type=1804 audit(1579880759.737:285): pid=27513 uid=0 auid=4294967295 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 op="invalid_pcr" cause="open_writers" comm="syz-executor.1" name="file0" dev="sda1" ino=16909 res=1
audit: type=1804 audit(1579880759.797:286): pid=27522 uid=0 auid=4294967295 ses=4294967295 subj=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 op="invalid_pcr" cause="open_writers" comm="syz-executor.1" name="file0" dev="sda1" ino=16909 res=1

Crashes (3):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/01/24 15:46 linux-4.14.y 8bac50406cca 2e95ab33 .config log report
ci2-linux-4-14 2019/11/17 06:13 linux-4.14.y 775d01b65b5d cdac920b .config log report
ci2-linux-4-14 2019/10/27 14:52 linux-4.14.y b98aebd29824 25bb509e .config log report