syzbot

IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
======================================================
WARNING: possible circular locking dependency detected
wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
4.19.191-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/9562 is trying to acquire lock:
000000003f26e7b9 (&sig->cred_guard_mutex){+.+.}, at: lock_trace fs/proc/base.c:402 [inline]
000000003f26e7b9 (&sig->cred_guard_mutex){+.+.}, at: proc_pid_syscall+0xb8/0x2f0 fs/proc/base.c:635

but task is already holding lock:
00000000da084160 (&p->lock){+.+.}, at: seq_read+0x6b/0x1160 fs/seq_file.c:161

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->lock){+.+.}:
IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready
       seq_read+0x6b/0x1160 fs/seq_file.c:161
       do_loop_readv_writev fs/read_write.c:701 [inline]
       do_loop_readv_writev fs/read_write.c:688 [inline]
       do_iter_read+0x471/0x630 fs/read_write.c:925
       vfs_readv+0xe5/0x150 fs/read_write.c:987
wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
       kernel_readv fs/splice.c:362 [inline]
       default_file_splice_read+0x457/0xa00 fs/splice.c:417
       do_splice_to+0x10e/0x160 fs/splice.c:881
       splice_direct_to_actor+0x2b9/0x8d0 fs/splice.c:959
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
       do_splice_direct+0x1a7/0x270 fs/splice.c:1068
IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
       do_sendfile+0x550/0xc30 fs/read_write.c:1447
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
       __do_sys_sendfile64 fs/read_write.c:1508 [inline]
       __se_sys_sendfile64+0x147/0x160 fs/read_write.c:1494
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #2 (sb_writers#3){.+.+}:
       sb_start_write include/linux/fs.h:1579 [inline]
       mnt_want_write+0x3a/0xb0 fs/namespace.c:360
       ovl_create_object+0x96/0x290 fs/overlayfs/dir.c:600
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
       lookup_open+0x893/0x1a20 fs/namei.c:3235
       do_last fs/namei.c:3327 [inline]
       path_openat+0x1094/0x2df0 fs/namei.c:3537
       do_filp_open+0x18c/0x3f0 fs/namei.c:3567
ieee80211 phy10: Selected rate control algorithm 'minstrel_ht'
       do_sys_open+0x3b3/0x520 fs/open.c:1085
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready

-> #1 (&ovl_i_mutex_dir_key[depth]){++++}:
       inode_lock_shared include/linux/fs.h:758 [inline]
       do_last fs/namei.c:3326 [inline]
       path_openat+0x17ec/0x2df0 fs/namei.c:3537
       do_filp_open+0x18c/0x3f0 fs/namei.c:3567
       do_open_execat+0x11d/0x5b0 fs/exec.c:853
wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
       __do_execve_file+0x1a8b/0x2360 fs/exec.c:1770
       do_execveat_common fs/exec.c:1879 [inline]
       do_execve+0x35/0x50 fs/exec.c:1896
       __do_sys_execve fs/exec.c:1977 [inline]
       __se_sys_execve fs/exec.c:1972 [inline]
       __x64_sys_execve+0x7c/0xa0 fs/exec.c:1972
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe
wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50

-> #0 (&sig->cred_guard_mutex){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:928 [inline]
       __mutex_lock+0xd7/0x1260 kernel/locking/mutex.c:1075
       lock_trace fs/proc/base.c:402 [inline]
       proc_pid_syscall+0xb8/0x2f0 fs/proc/base.c:635
       proc_single_show+0xeb/0x170 fs/proc/base.c:755
       seq_read+0x4be/0x1160 fs/seq_file.c:229
ieee80211 phy11: Selected rate control algorithm 'minstrel_ht'
       do_loop_readv_writev fs/read_write.c:701 [inline]
       do_loop_readv_writev fs/read_write.c:688 [inline]
       do_iter_read+0x471/0x630 fs/read_write.c:925
       vfs_readv+0xe5/0x150 fs/read_write.c:987
       kernel_readv fs/splice.c:362 [inline]
       default_file_splice_read+0x457/0xa00 fs/splice.c:417
       do_splice_to+0x10e/0x160 fs/splice.c:881
       splice_direct_to_actor+0x2b9/0x8d0 fs/splice.c:959
IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
       do_splice_direct+0x1a7/0x270 fs/splice.c:1068
       do_sendfile+0x550/0xc30 fs/read_write.c:1447
       __do_sys_sendfile64 fs/read_write.c:1508 [inline]
       __se_sys_sendfile64+0x147/0x160 fs/read_write.c:1494
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

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-executor.2/9562:
 #0: 0000000025209a34 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2779 [inline]
 #0: 0000000025209a34 (sb_writers#3){.+.+}, at: do_sendfile+0x97d/0xc30 fs/read_write.c:1446
 #1: 00000000da084160 (&p->lock){+.+.}, at: seq_read+0x6b/0x1160 fs/seq_file.c:161

stack backtrace:
CPU: 0 PID: 9562 Comm: syz-executor.2 Not tainted 4.19.191-syzkaller #0
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+0x1fc/0x2ef lib/dump_stack.c:118
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
 check_prev_add kernel/locking/lockdep.c:1866 [inline]
 check_prevs_add kernel/locking/lockdep.c:1979 [inline]
 validate_chain kernel/locking/lockdep.c:2420 [inline]
 __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 __mutex_lock_common kernel/locking/mutex.c:928 [inline]
 __mutex_lock+0xd7/0x1260 kernel/locking/mutex.c:1075
 lock_trace fs/proc/base.c:402 [inline]
 proc_pid_syscall+0xb8/0x2f0 fs/proc/base.c:635
 proc_single_show+0xeb/0x170 fs/proc/base.c:755
 seq_read+0x4be/0x1160 fs/seq_file.c:229
 do_loop_readv_writev fs/read_write.c:701 [inline]
 do_loop_readv_writev fs/read_write.c:688 [inline]
 do_iter_read+0x471/0x630 fs/read_write.c:925
 vfs_readv+0xe5/0x150 fs/read_write.c:987
IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready
wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
 kernel_readv fs/splice.c:362 [inline]
 default_file_splice_read+0x457/0xa00 fs/splice.c:417
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
ieee80211 phy12: Selected rate control algorithm 'minstrel_ht'
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
 do_splice_to+0x10e/0x160 fs/splice.c:881
 splice_direct_to_actor+0x2b9/0x8d0 fs/splice.c:959
wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50
ieee80211 phy13: Selected rate control algorithm 'minstrel_ht'
 do_splice_direct+0x1a7/0x270 fs/splice.c:1068
IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready
 do_sendfile+0x550/0xc30 fs/read_write.c:1447
 __do_sys_sendfile64 fs/read_write.c:1508 [inline]
 __se_sys_sendfile64+0x147/0x160 fs/read_write.c:1494
wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
RIP: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6087737188 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
overlayfs: './bus' not a directory
RAX: ffffffffffffffda RBX: 000000000056c038 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000007 R11: 0000000000000246 R12: 000000000056c038
R13: 00007ffd2d4933bf R14: 00007f6087737300 R15: 0000000000022000
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
audit: type=1800 audit(1621882336.927:2): pid=9691 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed comm="syz-executor.5" name="bus" dev="overlay" ino=13931 res=0
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
audit: type=1800 audit(1621882337.007:3): pid=9700 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed comm="syz-executor.4" name="bus" dev="overlay" ino=13947 res=0
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
audit: type=1800 audit(1621882337.698:4): pid=9845 uid=0 auid=4294967295 ses=4294967295 subj==unconfined op=collect_data cause=failed comm="syz-executor.3" name="bus" dev="overlay" ino=13908 res=0
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory
overlayfs: './bus' not a directory