* Re: possible circular locking dependency detected (bisected)
[not found] ` <812527981.484636.1472591145655.JavaMail.zimbra@redhat.com>
@ 2016-08-31 19:37 ` CAI Qian
2016-08-31 20:16 ` Rainer Weikusat
0 siblings, 1 reply; 3+ messages in thread
From: CAI Qian @ 2016-08-31 19:37 UTC (permalink / raw)
To: Rainer Weikusat, security
Cc: Miklos Szeredi, Eric Sandeen, Network Development
Reverted the patch below fixes this problem.
c845acb324aa85a39650a14e7696982ceea75dc1
af_unix: Fix splice-bind deadlock
CAI Qian
----- Original Message -----
> From: "CAI Qian" <caiqian@redhat.com>
> To: security@kernel.org
> Cc: "Miklos Szeredi" <mszeredi@redhat.com>, "Eric Sandeen" <esandeen@redhat.com>
> Sent: Tuesday, August 30, 2016 5:05:45 PM
> Subject: Re: possible circular locking dependency detected
>
> FYI, this one can only be reproduced using the overlayfs docker backend.
> The device-mapper works fine. The XFS below has ftype=1.
>
> # cp recvmsg01 /mnt
> # docker run -it -v /mnt/:/mnt/ rhel7 bash
> [root@c33c99aedd93 /]# mount
> overlay on / type overlay
> (rw,relatime,seclabel,lowerdir=l/I5VXL74ENBNAEARZ4M2SIN3XD6:l/KZGBKPXLDXUGHYWMERFUBM4FRP,upperdir=9a7c1f735166b1f63d220b4b6c59cc37f3922719ef810c97182b814c1ab336df/diff,workdir=9a7c1f735166b1f63d220b4b6c59cc37f3922719ef810c97182b814c1ab336df/work)
> ...
> [root@c33c99aedd93 /]# /mnt/recvmsg01
> CAI Qian
>
> ----- Original Message -----
> > From: "CAI Qian" <caiqian@redhat.com>
> > To: security@kernel.org
> > Sent: Friday, August 26, 2016 10:50:57 AM
> > Subject: possible circular locking dependency detected
> >
> > FYI, just want to give a head up to see if there is anything obvious so
> > we can avoid a possible DoS somehow.
> >
> > Running the LTP syscalls tests inside a container until this test trigger
> > below,
> > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/recvmsg/recvmsg01.c
> >
> > [ 4441.904103] open04 (42409) used greatest stack depth: 20552 bytes left
> > [ 4605.419167]
> > [ 4605.420831] ======================================================
> > [ 4605.427727] [ INFO: possible circular locking dependency detected ]
> > [ 4605.434720] 4.8.0-rc3+ #3 Not tainted
> > [ 4605.438803] -------------------------------------------------------
> > [ 4605.445796] recvmsg01/42878 is trying to acquire lock:
> > [ 4605.451528] (sb_writers#8){.+.+.+}, at: [<ffffffff816a6d34>]
> > __sb_start_write+0xb4/0xf0
> > [ 4605.460642]
> > [ 4605.460642] but task is already holding lock:
> > [ 4605.467150] (&u->readlock){+.+.+.}, at: [<ffffffff825242e9>]
> > unix_bind+0x299/0xdf0
> > [ 4605.475749]
> > [ 4605.475749] which lock already depends on the new lock.
> > [ 4605.475749]
> > [ 4605.484882]
> > [ 4605.484882] the existing dependency chain (in reverse order) is:
> > [ 4605.493234]
> > [ 4605.493234] -> #2 (&u->readlock){+.+.+.}:
> > [ 4605.497943] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> > [ 4605.504659] [<ffffffff826948fd>]
> > mutex_lock_interruptible_nested+0xdd/0x920
> > [ 4605.513119] [<ffffffff825242e9>] unix_bind+0x299/0xdf0
> > [ 4605.519540] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
> > [ 4605.525964] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
> > [ 4605.531998] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
> > [ 4605.538811] [<ffffffff8269e6bf>] return_from_SYSCALL_64+0x0/0x7a
> > [ 4605.546203]
> > [ 4605.546203] -> #1 (&type->i_mutex_dir_key#3/1){+.+.+.}:
> > [ 4605.552292] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> > [ 4605.559002] [<ffffffff812a0f6e>] down_write_nested+0x5e/0xe0
> > [ 4605.566008] [<ffffffff816d1b55>] filename_create+0x155/0x470
> > [ 4605.573013] [<ffffffff816d403f>] SyS_mkdir+0xaf/0x1f0
> > [ 4605.579339] [<ffffffff8269e5fc>]
> > entry_SYSCALL_64_fastpath+0x1f/0xbd
> > [ 4605.587119]
> > [ 4605.587119] -> #0 (sb_writers#8){.+.+.+}:
> > [ 4605.591835] [<ffffffff812b31f3>] __lock_acquire+0x3043/0x3dd0
> > [ 4605.598935] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> > [ 4605.605646] [<ffffffff812a138f>] percpu_down_read+0x4f/0xa0
> > [ 4605.612552] [<ffffffff816a6d34>] __sb_start_write+0xb4/0xf0
> > [ 4605.619459] [<ffffffff817050d1>] mnt_want_write+0x41/0xb0
> > [ 4605.626173] [<ffffffffa0ce4be6>] ovl_want_write+0x76/0xa0
> > [overlay]
> > [ 4605.633860] [<ffffffffa0cebd63>] ovl_create_object+0xa3/0x2d0
> > [overlay]
> > [ 4605.641942] [<ffffffffa0cebfc1>] ovl_mknod+0x31/0x40 [overlay]
> > [ 4605.649138] [<ffffffff816c16db>] vfs_mknod+0x34b/0x560
> > [ 4605.655570] [<ffffffff8252451a>] unix_bind+0x4ca/0xdf0
> > [ 4605.661991] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
> > [ 4605.668412] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
> > [ 4605.674456] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
> > [ 4605.681266] [<ffffffff8269e6bf>] return_from_SYSCALL_64+0x0/0x7a
> > [ 4605.688657]
> > [ 4605.688657] other info that might help us debug this:
> > [ 4605.688657]
> > [ 4605.697590] Chain exists of:
> > [ 4605.697590] sb_writers#8 --> &type->i_mutex_dir_key#3/1 -->
> > &u->readlock
> > [ 4605.697590]
> > [ 4605.707287] Possible unsafe locking scenario:
> > [ 4605.707287]
> > [ 4605.713890] CPU0 CPU1
> > [ 4605.718943] ---- ----
> > [ 4605.723995] lock(&u->readlock);
> > [ 4605.727708]
> > lock(&type->i_mutex_dir_key#3/1);
> > [ 4605.735613] lock(&u->readlock);
> > [ 4605.742146] lock(sb_writers#8);
> > [ 4605.745880]
> > [ 4605.745880] *** DEADLOCK ***
> > [ 4605.745880]
> > [ 4605.752486] 3 locks held by recvmsg01/42878:
> > [ 4605.757247] #0: (sb_writers#13){.+.+.+}, at: [<ffffffff816a6d34>]
> > __sb_start_write+0xb4/0xf0
> > [ 4605.766930] #1: (&sb->s_type->i_mutex_key#16/1){+.+.+.}, at:
> > [<ffffffff816d1b55>] filename_create+0x155/0x470
> > [ 4605.778269] #2: (&u->readlock){+.+.+.}, at: [<ffffffff825242e9>]
> > unix_bind+0x299/0xdf0
> > [ 4605.787350]
> > [ 4605.787350] stack backtrace:
> > [ 4605.792213] CPU: 38 PID: 42878 Comm: recvmsg01 Not tainted 4.8.0-rc3+ #3
> > [ 4605.799691] Hardware name: Intel Corporation S2600WTT/S2600WTT, BIOS
> > GRNDSDP1.86B.0044.R00.1501191641 01/19/2015
> > [ 4605.811047] 0000000000000000 000000009cc8af78 ffff8803c2c37770
> > ffffffff81a63fb1
> > [ 4605.819341] ffffffff842a0590 ffffffff842c0ae0 ffff8803c2c377c0
> > ffffffff812ac0d6
> > [ 4605.827633] ffffffff842a0590 ffff8804619f0d08 ffff8803c2c378e0
> > ffff8804619f0d08
> > [ 4605.835927] Call Trace:
> > [ 4605.838656] [<ffffffff81a63fb1>] dump_stack+0x85/0xc4
> > [ 4605.844390] [<ffffffff812ac0d6>] print_circular_bug+0x356/0x460
> > [ 4605.851092] [<ffffffff812b31f3>] __lock_acquire+0x3043/0x3dd0
> > [ 4605.857602] [<ffffffff81632710>] ? kfree+0x310/0x370
> > [ 4605.863238] [<ffffffff812b01b0>] ?
> > debug_check_no_locks_freed+0x2c0/0x2c0
> > [ 4605.870912] [<ffffffff818be5f2>] ? avc_has_perm+0xa2/0x480
> > [ 4605.877130] [<ffffffff818be792>] ? avc_has_perm+0x242/0x480
> > [ 4605.883443] [<ffffffff818be7b1>] ? avc_has_perm+0x261/0x480
> > [ 4605.889758] [<ffffffff818be5f2>] ? avc_has_perm+0xa2/0x480
> > [ 4605.895977] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> > [ 4605.902098] [<ffffffff816a6d34>] ? __sb_start_write+0xb4/0xf0
> > [ 4605.908607] [<ffffffff812a138f>] percpu_down_read+0x4f/0xa0
> > [ 4605.914921] [<ffffffff816a6d34>] ? __sb_start_write+0xb4/0xf0
> > [ 4605.921429] [<ffffffff816a6d34>] __sb_start_write+0xb4/0xf0
> > [ 4605.927742] [<ffffffff817050d1>] mnt_want_write+0x41/0xb0
> > [ 4605.933875] [<ffffffffa0ce4be6>] ovl_want_write+0x76/0xa0 [overlay]
> > [ 4605.940967] [<ffffffffa0cebd63>] ovl_create_object+0xa3/0x2d0 [overlay]
> > [ 4605.948445] [<ffffffffa0cebcc0>] ?
> > ovl_create_or_link.part.3+0xc70/0xc70
> > [overlay]
> > [ 4605.956990] [<ffffffff818c55c2>] ? selinux_inode_mknod+0x42/0x80
> > [ 4605.963790] [<ffffffffa0cebfc1>] ovl_mknod+0x31/0x40 [overlay]
> > [ 4605.970395] [<ffffffff816c16db>] vfs_mknod+0x34b/0x560
> > [ 4605.976224] [<ffffffff8252451a>] unix_bind+0x4ca/0xdf0
> > [ 4605.982053] [<ffffffff82524050>] ? unix_autobind.isra.24+0x600/0x600
> > [ 4605.989244] [<ffffffff815a7d86>] ? __might_fault+0xf6/0x1b0
> > [ 4605.995550] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
> > [ 4606.001381] [<ffffffff821f6740>] ?
> > move_addr_to_kernel.part.13+0xe0/0xe0
> > [ 4606.008958] [<ffffffff813d1af5>] ? __audit_syscall_entry+0x325/0x6f0
> > [ 4606.016144] [<ffffffff813d1af5>] ? __audit_syscall_entry+0x325/0x6f0
> > [ 4606.023332] [<ffffffff81007a02>] ? do_syscall_64+0x52/0x500
> > [ 4606.029645] [<ffffffff821fb6f0>] ? SyS_socketpair+0x470/0x470
> > [ 4606.036154] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
> > [ 4606.041595] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
> > [ 4606.047813] [<ffffffff8100401a>] ? trace_hardirqs_on_thunk+0x1a/0x1c
> > [ 4606.055000] [<ffffffff8269e6bf>] entry_SYSCALL64_slow_path+0x25/0x25
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: possible circular locking dependency detected (bisected)
2016-08-31 19:37 ` possible circular locking dependency detected (bisected) CAI Qian
@ 2016-08-31 20:16 ` Rainer Weikusat
2016-09-01 19:14 ` CAI Qian
0 siblings, 1 reply; 3+ messages in thread
From: Rainer Weikusat @ 2016-08-31 20:16 UTC (permalink / raw)
To: CAI Qian
Cc: Rainer Weikusat, security, Miklos Szeredi, Eric Sandeen,
Network Development
CAI Qian <caiqian@redhat.com> writes:
> Reverted the patch below fixes this problem.
>
> c845acb324aa85a39650a14e7696982ceea75dc1
> af_unix: Fix splice-bind deadlock
Reverting a patch fixing one deadlock in order to avoid another deadlock
leaves the 'net situation' unchanged. The idea of the other patch was to
change unix_mknod such that it doesn't do __sb_start_write with
u->readlock held anymore. As far as I understand the output below,
overlayfs introduce an additional codepath where unix_mknod end up doing
__sb_start_write again. That's already the original deadlock re-added,
cf,
B: splice() from a pipe to /mnt/regular_file
does sb_start_write() on /mnt
C: try to freeze /mnt
wait for B to finish with /mnt
A: bind() try to bind our socket to /mnt/new_socket_name
lock our socket, see it not bound yet
decide that it needs to create something in /mnt
try to do sb_start_write() on /mnt, block (it's
waiting for C).
D: splice() from the same pipe to our socket
lock the pipe, see that socket is connected
try to lock the socket, block waiting for A
B: get around to actually feeding a chunk from
pipe to file, try to lock the pipe. Deadlock.
as A will again acquire the readlock and then call __sb_start_write.
>
> CAI Qian
>
> ----- Original Message -----
>> From: "CAI Qian" <caiqian@redhat.com>
>> To: security@kernel.org
>> Cc: "Miklos Szeredi" <mszeredi@redhat.com>, "Eric Sandeen" <esandeen@redhat.com>
>> Sent: Tuesday, August 30, 2016 5:05:45 PM
>> Subject: Re: possible circular locking dependency detected
>>
>> FYI, this one can only be reproduced using the overlayfs docker backend.
>> The device-mapper works fine. The XFS below has ftype=1.
>>
>> # cp recvmsg01 /mnt
>> # docker run -it -v /mnt/:/mnt/ rhel7 bash
>> [root@c33c99aedd93 /]# mount
>> overlay on / type overlay
>> (rw,relatime,seclabel,lowerdir=l/I5VXL74ENBNAEARZ4M2SIN3XD6:l/KZGBKPXLDXUGHYWMERFUBM4FRP,upperdir=9a7c1f735166b1f63d220b4b6c59cc37f3922719ef810c97182b814c1ab336df/diff,workdir=9a7c1f735166b1f63d220b4b6c59cc37f3922719ef810c97182b814c1ab336df/work)
>> ...
>> [root@c33c99aedd93 /]# /mnt/recvmsg01
>> CAI Qian
>>
>> ----- Original Message -----
>> > From: "CAI Qian" <caiqian@redhat.com>
>> > To: security@kernel.org
>> > Sent: Friday, August 26, 2016 10:50:57 AM
>> > Subject: possible circular locking dependency detected
>> >
>> > FYI, just want to give a head up to see if there is anything obvious so
>> > we can avoid a possible DoS somehow.
>> >
>> > Running the LTP syscalls tests inside a container until this test trigger
>> > below,
>> > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/recvmsg/recvmsg01.c
>> >
>> > [ 4441.904103] open04 (42409) used greatest stack depth: 20552 bytes left
>> > [ 4605.419167]
>> > [ 4605.420831] ======================================================
>> > [ 4605.427727] [ INFO: possible circular locking dependency detected ]
>> > [ 4605.434720] 4.8.0-rc3+ #3 Not tainted
>> > [ 4605.438803] -------------------------------------------------------
>> > [ 4605.445796] recvmsg01/42878 is trying to acquire lock:
>> > [ 4605.451528] (sb_writers#8){.+.+.+}, at: [<ffffffff816a6d34>]
>> > __sb_start_write+0xb4/0xf0
>> > [ 4605.460642]
>> > [ 4605.460642] but task is already holding lock:
>> > [ 4605.467150] (&u->readlock){+.+.+.}, at: [<ffffffff825242e9>]
>> > unix_bind+0x299/0xdf0
>> > [ 4605.475749]
>> > [ 4605.475749] which lock already depends on the new lock.
>> > [ 4605.475749]
>> > [ 4605.484882]
>> > [ 4605.484882] the existing dependency chain (in reverse order) is:
>> > [ 4605.493234]
>> > [ 4605.493234] -> #2 (&u->readlock){+.+.+.}:
>> > [ 4605.497943] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
>> > [ 4605.504659] [<ffffffff826948fd>]
>> > mutex_lock_interruptible_nested+0xdd/0x920
>> > [ 4605.513119] [<ffffffff825242e9>] unix_bind+0x299/0xdf0
>> > [ 4605.519540] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
>> > [ 4605.525964] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
>> > [ 4605.531998] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
>> > [ 4605.538811] [<ffffffff8269e6bf>] return_from_SYSCALL_64+0x0/0x7a
>> > [ 4605.546203]
>> > [ 4605.546203] -> #1 (&type->i_mutex_dir_key#3/1){+.+.+.}:
>> > [ 4605.552292] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
>> > [ 4605.559002] [<ffffffff812a0f6e>] down_write_nested+0x5e/0xe0
>> > [ 4605.566008] [<ffffffff816d1b55>] filename_create+0x155/0x470
>> > [ 4605.573013] [<ffffffff816d403f>] SyS_mkdir+0xaf/0x1f0
>> > [ 4605.579339] [<ffffffff8269e5fc>]
>> > entry_SYSCALL_64_fastpath+0x1f/0xbd
>> > [ 4605.587119]
>> > [ 4605.587119] -> #0 (sb_writers#8){.+.+.+}:
>> > [ 4605.591835] [<ffffffff812b31f3>] __lock_acquire+0x3043/0x3dd0
>> > [ 4605.598935] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
>> > [ 4605.605646] [<ffffffff812a138f>] percpu_down_read+0x4f/0xa0
>> > [ 4605.612552] [<ffffffff816a6d34>] __sb_start_write+0xb4/0xf0
>> > [ 4605.619459] [<ffffffff817050d1>] mnt_want_write+0x41/0xb0
>> > [ 4605.626173] [<ffffffffa0ce4be6>] ovl_want_write+0x76/0xa0
>> > [overlay]
>> > [ 4605.633860] [<ffffffffa0cebd63>] ovl_create_object+0xa3/0x2d0
>> > [overlay]
>> > [ 4605.641942] [<ffffffffa0cebfc1>] ovl_mknod+0x31/0x40 [overlay]
>> > [ 4605.649138] [<ffffffff816c16db>] vfs_mknod+0x34b/0x560
>> > [ 4605.655570] [<ffffffff8252451a>] unix_bind+0x4ca/0xdf0
>> > [ 4605.661991] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
>> > [ 4605.668412] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
>> > [ 4605.674456] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
>> > [ 4605.681266] [<ffffffff8269e6bf>] return_from_SYSCALL_64+0x0/0x7a
>> > [ 4605.688657]
>> > [ 4605.688657] other info that might help us debug this:
>> > [ 4605.688657]
>> > [ 4605.697590] Chain exists of:
>> > [ 4605.697590] sb_writers#8 --> &type->i_mutex_dir_key#3/1 -->
>> > &u->readlock
>> > [ 4605.697590]
>> > [ 4605.707287] Possible unsafe locking scenario:
>> > [ 4605.707287]
>> > [ 4605.713890] CPU0 CPU1
>> > [ 4605.718943] ---- ----
>> > [ 4605.723995] lock(&u->readlock);
>> > [ 4605.727708]
>> > lock(&type->i_mutex_dir_key#3/1);
>> > [ 4605.735613] lock(&u->readlock);
>> > [ 4605.742146] lock(sb_writers#8);
>> > [ 4605.745880]
>> > [ 4605.745880] *** DEADLOCK ***
>> > [ 4605.745880]
>> > [ 4605.752486] 3 locks held by recvmsg01/42878:
>> > [ 4605.757247] #0: (sb_writers#13){.+.+.+}, at: [<ffffffff816a6d34>]
>> > __sb_start_write+0xb4/0xf0
>> > [ 4605.766930] #1: (&sb->s_type->i_mutex_key#16/1){+.+.+.}, at:
>> > [<ffffffff816d1b55>] filename_create+0x155/0x470
>> > [ 4605.778269] #2: (&u->readlock){+.+.+.}, at: [<ffffffff825242e9>]
>> > unix_bind+0x299/0xdf0
>> > [ 4605.787350]
>> > [ 4605.787350] stack backtrace:
>> > [ 4605.792213] CPU: 38 PID: 42878 Comm: recvmsg01 Not tainted 4.8.0-rc3+ #3
>> > [ 4605.799691] Hardware name: Intel Corporation S2600WTT/S2600WTT, BIOS
>> > GRNDSDP1.86B.0044.R00.1501191641 01/19/2015
>> > [ 4605.811047] 0000000000000000 000000009cc8af78 ffff8803c2c37770
>> > ffffffff81a63fb1
>> > [ 4605.819341] ffffffff842a0590 ffffffff842c0ae0 ffff8803c2c377c0
>> > ffffffff812ac0d6
>> > [ 4605.827633] ffffffff842a0590 ffff8804619f0d08 ffff8803c2c378e0
>> > ffff8804619f0d08
>> > [ 4605.835927] Call Trace:
>> > [ 4605.838656] [<ffffffff81a63fb1>] dump_stack+0x85/0xc4
>> > [ 4605.844390] [<ffffffff812ac0d6>] print_circular_bug+0x356/0x460
>> > [ 4605.851092] [<ffffffff812b31f3>] __lock_acquire+0x3043/0x3dd0
>> > [ 4605.857602] [<ffffffff81632710>] ? kfree+0x310/0x370
>> > [ 4605.863238] [<ffffffff812b01b0>] ?
>> > debug_check_no_locks_freed+0x2c0/0x2c0
>> > [ 4605.870912] [<ffffffff818be5f2>] ? avc_has_perm+0xa2/0x480
>> > [ 4605.877130] [<ffffffff818be792>] ? avc_has_perm+0x242/0x480
>> > [ 4605.883443] [<ffffffff818be7b1>] ? avc_has_perm+0x261/0x480
>> > [ 4605.889758] [<ffffffff818be5f2>] ? avc_has_perm+0xa2/0x480
>> > [ 4605.895977] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
>> > [ 4605.902098] [<ffffffff816a6d34>] ? __sb_start_write+0xb4/0xf0
>> > [ 4605.908607] [<ffffffff812a138f>] percpu_down_read+0x4f/0xa0
>> > [ 4605.914921] [<ffffffff816a6d34>] ? __sb_start_write+0xb4/0xf0
>> > [ 4605.921429] [<ffffffff816a6d34>] __sb_start_write+0xb4/0xf0
>> > [ 4605.927742] [<ffffffff817050d1>] mnt_want_write+0x41/0xb0
>> > [ 4605.933875] [<ffffffffa0ce4be6>] ovl_want_write+0x76/0xa0 [overlay]
>> > [ 4605.940967] [<ffffffffa0cebd63>] ovl_create_object+0xa3/0x2d0 [overlay]
>> > [ 4605.948445] [<ffffffffa0cebcc0>] ?
>> > ovl_create_or_link.part.3+0xc70/0xc70
>> > [overlay]
>> > [ 4605.956990] [<ffffffff818c55c2>] ? selinux_inode_mknod+0x42/0x80
>> > [ 4605.963790] [<ffffffffa0cebfc1>] ovl_mknod+0x31/0x40 [overlay]
>> > [ 4605.970395] [<ffffffff816c16db>] vfs_mknod+0x34b/0x560
>> > [ 4605.976224] [<ffffffff8252451a>] unix_bind+0x4ca/0xdf0
>> > [ 4605.982053] [<ffffffff82524050>] ? unix_autobind.isra.24+0x600/0x600
>> > [ 4605.989244] [<ffffffff815a7d86>] ? __might_fault+0xf6/0x1b0
>> > [ 4605.995550] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
>> > [ 4606.001381] [<ffffffff821f6740>] ?
>> > move_addr_to_kernel.part.13+0xe0/0xe0
>> > [ 4606.008958] [<ffffffff813d1af5>] ? __audit_syscall_entry+0x325/0x6f0
>> > [ 4606.016144] [<ffffffff813d1af5>] ? __audit_syscall_entry+0x325/0x6f0
>> > [ 4606.023332] [<ffffffff81007a02>] ? do_syscall_64+0x52/0x500
>> > [ 4606.029645] [<ffffffff821fb6f0>] ? SyS_socketpair+0x470/0x470
>> > [ 4606.036154] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
>> > [ 4606.041595] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
>> > [ 4606.047813] [<ffffffff8100401a>] ? trace_hardirqs_on_thunk+0x1a/0x1c
>> > [ 4606.055000] [<ffffffff8269e6bf>] entry_SYSCALL64_slow_path+0x25/0x25
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: possible circular locking dependency detected (bisected)
2016-08-31 20:16 ` Rainer Weikusat
@ 2016-09-01 19:14 ` CAI Qian
0 siblings, 0 replies; 3+ messages in thread
From: CAI Qian @ 2016-09-01 19:14 UTC (permalink / raw)
To: Rainer Weikusat
Cc: Rainer Weikusat, security, Miklos Szeredi, Eric Sandeen,
Network Development
FYI, the regression is tracked here,
https://bugzilla.kernel.org/show_bug.cgi?id=155781
CAI Qian
----- Original Message -----
> From: "Rainer Weikusat" <rweikusat@cyberadapt.com>
> To: "CAI Qian" <caiqian@redhat.com>
> Cc: "Rainer Weikusat" <rweikusat@mobileactivedefense.com>, security@kernel.org, "Miklos Szeredi"
> <mszeredi@redhat.com>, "Eric Sandeen" <esandeen@redhat.com>, "Network Development" <netdev@vger.kernel.org>
> Sent: Wednesday, August 31, 2016 4:16:25 PM
> Subject: Re: possible circular locking dependency detected (bisected)
>
> CAI Qian <caiqian@redhat.com> writes:
> > Reverted the patch below fixes this problem.
> >
> > c845acb324aa85a39650a14e7696982ceea75dc1
> > af_unix: Fix splice-bind deadlock
>
> Reverting a patch fixing one deadlock in order to avoid another deadlock
> leaves the 'net situation' unchanged. The idea of the other patch was to
> change unix_mknod such that it doesn't do __sb_start_write with
> u->readlock held anymore. As far as I understand the output below,
> overlayfs introduce an additional codepath where unix_mknod end up doing
> __sb_start_write again. That's already the original deadlock re-added,
> cf,
>
> B: splice() from a pipe to /mnt/regular_file
> does sb_start_write() on /mnt
> C: try to freeze /mnt
> wait for B to finish with /mnt
> A: bind() try to bind our socket to /mnt/new_socket_name
> lock our socket, see it not bound yet
> decide that it needs to create something in /mnt
> try to do sb_start_write() on /mnt, block (it's
> waiting for C).
> D: splice() from the same pipe to our socket
> lock the pipe, see that socket is connected
> try to lock the socket, block waiting for A
> B: get around to actually feeding a chunk from
> pipe to file, try to lock the pipe. Deadlock.
>
>
> as A will again acquire the readlock and then call __sb_start_write.
>
> >
> > CAI Qian
> >
> > ----- Original Message -----
> >> From: "CAI Qian" <caiqian@redhat.com>
> >> To: security@kernel.org
> >> Cc: "Miklos Szeredi" <mszeredi@redhat.com>, "Eric Sandeen"
> >> <esandeen@redhat.com>
> >> Sent: Tuesday, August 30, 2016 5:05:45 PM
> >> Subject: Re: possible circular locking dependency detected
> >>
> >> FYI, this one can only be reproduced using the overlayfs docker backend.
> >> The device-mapper works fine. The XFS below has ftype=1.
> >>
> >> # cp recvmsg01 /mnt
> >> # docker run -it -v /mnt/:/mnt/ rhel7 bash
> >> [root@c33c99aedd93 /]# mount
> >> overlay on / type overlay
> >> (rw,relatime,seclabel,lowerdir=l/I5VXL74ENBNAEARZ4M2SIN3XD6:l/KZGBKPXLDXUGHYWMERFUBM4FRP,upperdir=9a7c1f735166b1f63d220b4b6c59cc37f3922719ef810c97182b814c1ab336df/diff,workdir=9a7c1f735166b1f63d220b4b6c59cc37f3922719ef810c97182b814c1ab336df/work)
> >> ...
> >> [root@c33c99aedd93 /]# /mnt/recvmsg01
> >> CAI Qian
> >>
> >> ----- Original Message -----
> >> > From: "CAI Qian" <caiqian@redhat.com>
> >> > To: security@kernel.org
> >> > Sent: Friday, August 26, 2016 10:50:57 AM
> >> > Subject: possible circular locking dependency detected
> >> >
> >> > FYI, just want to give a head up to see if there is anything obvious so
> >> > we can avoid a possible DoS somehow.
> >> >
> >> > Running the LTP syscalls tests inside a container until this test
> >> > trigger
> >> > below,
> >> > https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/recvmsg/recvmsg01.c
> >> >
> >> > [ 4441.904103] open04 (42409) used greatest stack depth: 20552 bytes
> >> > left
> >> > [ 4605.419167]
> >> > [ 4605.420831] ======================================================
> >> > [ 4605.427727] [ INFO: possible circular locking dependency detected ]
> >> > [ 4605.434720] 4.8.0-rc3+ #3 Not tainted
> >> > [ 4605.438803] -------------------------------------------------------
> >> > [ 4605.445796] recvmsg01/42878 is trying to acquire lock:
> >> > [ 4605.451528] (sb_writers#8){.+.+.+}, at: [<ffffffff816a6d34>]
> >> > __sb_start_write+0xb4/0xf0
> >> > [ 4605.460642]
> >> > [ 4605.460642] but task is already holding lock:
> >> > [ 4605.467150] (&u->readlock){+.+.+.}, at: [<ffffffff825242e9>]
> >> > unix_bind+0x299/0xdf0
> >> > [ 4605.475749]
> >> > [ 4605.475749] which lock already depends on the new lock.
> >> > [ 4605.475749]
> >> > [ 4605.484882]
> >> > [ 4605.484882] the existing dependency chain (in reverse order) is:
> >> > [ 4605.493234]
> >> > [ 4605.493234] -> #2 (&u->readlock){+.+.+.}:
> >> > [ 4605.497943] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> >> > [ 4605.504659] [<ffffffff826948fd>]
> >> > mutex_lock_interruptible_nested+0xdd/0x920
> >> > [ 4605.513119] [<ffffffff825242e9>] unix_bind+0x299/0xdf0
> >> > [ 4605.519540] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
> >> > [ 4605.525964] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
> >> > [ 4605.531998] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
> >> > [ 4605.538811] [<ffffffff8269e6bf>]
> >> > return_from_SYSCALL_64+0x0/0x7a
> >> > [ 4605.546203]
> >> > [ 4605.546203] -> #1 (&type->i_mutex_dir_key#3/1){+.+.+.}:
> >> > [ 4605.552292] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> >> > [ 4605.559002] [<ffffffff812a0f6e>] down_write_nested+0x5e/0xe0
> >> > [ 4605.566008] [<ffffffff816d1b55>] filename_create+0x155/0x470
> >> > [ 4605.573013] [<ffffffff816d403f>] SyS_mkdir+0xaf/0x1f0
> >> > [ 4605.579339] [<ffffffff8269e5fc>]
> >> > entry_SYSCALL_64_fastpath+0x1f/0xbd
> >> > [ 4605.587119]
> >> > [ 4605.587119] -> #0 (sb_writers#8){.+.+.+}:
> >> > [ 4605.591835] [<ffffffff812b31f3>] __lock_acquire+0x3043/0x3dd0
> >> > [ 4605.598935] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> >> > [ 4605.605646] [<ffffffff812a138f>] percpu_down_read+0x4f/0xa0
> >> > [ 4605.612552] [<ffffffff816a6d34>] __sb_start_write+0xb4/0xf0
> >> > [ 4605.619459] [<ffffffff817050d1>] mnt_want_write+0x41/0xb0
> >> > [ 4605.626173] [<ffffffffa0ce4be6>] ovl_want_write+0x76/0xa0
> >> > [overlay]
> >> > [ 4605.633860] [<ffffffffa0cebd63>] ovl_create_object+0xa3/0x2d0
> >> > [overlay]
> >> > [ 4605.641942] [<ffffffffa0cebfc1>] ovl_mknod+0x31/0x40 [overlay]
> >> > [ 4605.649138] [<ffffffff816c16db>] vfs_mknod+0x34b/0x560
> >> > [ 4605.655570] [<ffffffff8252451a>] unix_bind+0x4ca/0xdf0
> >> > [ 4605.661991] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
> >> > [ 4605.668412] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
> >> > [ 4605.674456] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
> >> > [ 4605.681266] [<ffffffff8269e6bf>]
> >> > return_from_SYSCALL_64+0x0/0x7a
> >> > [ 4605.688657]
> >> > [ 4605.688657] other info that might help us debug this:
> >> > [ 4605.688657]
> >> > [ 4605.697590] Chain exists of:
> >> > [ 4605.697590] sb_writers#8 --> &type->i_mutex_dir_key#3/1 -->
> >> > &u->readlock
> >> > [ 4605.697590]
> >> > [ 4605.707287] Possible unsafe locking scenario:
> >> > [ 4605.707287]
> >> > [ 4605.713890] CPU0 CPU1
> >> > [ 4605.718943] ---- ----
> >> > [ 4605.723995] lock(&u->readlock);
> >> > [ 4605.727708]
> >> > lock(&type->i_mutex_dir_key#3/1);
> >> > [ 4605.735613] lock(&u->readlock);
> >> > [ 4605.742146] lock(sb_writers#8);
> >> > [ 4605.745880]
> >> > [ 4605.745880] *** DEADLOCK ***
> >> > [ 4605.745880]
> >> > [ 4605.752486] 3 locks held by recvmsg01/42878:
> >> > [ 4605.757247] #0: (sb_writers#13){.+.+.+}, at: [<ffffffff816a6d34>]
> >> > __sb_start_write+0xb4/0xf0
> >> > [ 4605.766930] #1: (&sb->s_type->i_mutex_key#16/1){+.+.+.}, at:
> >> > [<ffffffff816d1b55>] filename_create+0x155/0x470
> >> > [ 4605.778269] #2: (&u->readlock){+.+.+.}, at: [<ffffffff825242e9>]
> >> > unix_bind+0x299/0xdf0
> >> > [ 4605.787350]
> >> > [ 4605.787350] stack backtrace:
> >> > [ 4605.792213] CPU: 38 PID: 42878 Comm: recvmsg01 Not tainted 4.8.0-rc3+
> >> > #3
> >> > [ 4605.799691] Hardware name: Intel Corporation S2600WTT/S2600WTT, BIOS
> >> > GRNDSDP1.86B.0044.R00.1501191641 01/19/2015
> >> > [ 4605.811047] 0000000000000000 000000009cc8af78 ffff8803c2c37770
> >> > ffffffff81a63fb1
> >> > [ 4605.819341] ffffffff842a0590 ffffffff842c0ae0 ffff8803c2c377c0
> >> > ffffffff812ac0d6
> >> > [ 4605.827633] ffffffff842a0590 ffff8804619f0d08 ffff8803c2c378e0
> >> > ffff8804619f0d08
> >> > [ 4605.835927] Call Trace:
> >> > [ 4605.838656] [<ffffffff81a63fb1>] dump_stack+0x85/0xc4
> >> > [ 4605.844390] [<ffffffff812ac0d6>] print_circular_bug+0x356/0x460
> >> > [ 4605.851092] [<ffffffff812b31f3>] __lock_acquire+0x3043/0x3dd0
> >> > [ 4605.857602] [<ffffffff81632710>] ? kfree+0x310/0x370
> >> > [ 4605.863238] [<ffffffff812b01b0>] ?
> >> > debug_check_no_locks_freed+0x2c0/0x2c0
> >> > [ 4605.870912] [<ffffffff818be5f2>] ? avc_has_perm+0xa2/0x480
> >> > [ 4605.877130] [<ffffffff818be792>] ? avc_has_perm+0x242/0x480
> >> > [ 4605.883443] [<ffffffff818be7b1>] ? avc_has_perm+0x261/0x480
> >> > [ 4605.889758] [<ffffffff818be5f2>] ? avc_has_perm+0xa2/0x480
> >> > [ 4605.895977] [<ffffffff812b4b5a>] lock_acquire+0x1fa/0x440
> >> > [ 4605.902098] [<ffffffff816a6d34>] ? __sb_start_write+0xb4/0xf0
> >> > [ 4605.908607] [<ffffffff812a138f>] percpu_down_read+0x4f/0xa0
> >> > [ 4605.914921] [<ffffffff816a6d34>] ? __sb_start_write+0xb4/0xf0
> >> > [ 4605.921429] [<ffffffff816a6d34>] __sb_start_write+0xb4/0xf0
> >> > [ 4605.927742] [<ffffffff817050d1>] mnt_want_write+0x41/0xb0
> >> > [ 4605.933875] [<ffffffffa0ce4be6>] ovl_want_write+0x76/0xa0 [overlay]
> >> > [ 4605.940967] [<ffffffffa0cebd63>] ovl_create_object+0xa3/0x2d0
> >> > [overlay]
> >> > [ 4605.948445] [<ffffffffa0cebcc0>] ?
> >> > ovl_create_or_link.part.3+0xc70/0xc70
> >> > [overlay]
> >> > [ 4605.956990] [<ffffffff818c55c2>] ? selinux_inode_mknod+0x42/0x80
> >> > [ 4605.963790] [<ffffffffa0cebfc1>] ovl_mknod+0x31/0x40 [overlay]
> >> > [ 4605.970395] [<ffffffff816c16db>] vfs_mknod+0x34b/0x560
> >> > [ 4605.976224] [<ffffffff8252451a>] unix_bind+0x4ca/0xdf0
> >> > [ 4605.982053] [<ffffffff82524050>] ? unix_autobind.isra.24+0x600/0x600
> >> > [ 4605.989244] [<ffffffff815a7d86>] ? __might_fault+0xf6/0x1b0
> >> > [ 4605.995550] [<ffffffff821f6918>] SYSC_bind+0x1d8/0x240
> >> > [ 4606.001381] [<ffffffff821f6740>] ?
> >> > move_addr_to_kernel.part.13+0xe0/0xe0
> >> > [ 4606.008958] [<ffffffff813d1af5>] ? __audit_syscall_entry+0x325/0x6f0
> >> > [ 4606.016144] [<ffffffff813d1af5>] ? __audit_syscall_entry+0x325/0x6f0
> >> > [ 4606.023332] [<ffffffff81007a02>] ? do_syscall_64+0x52/0x500
> >> > [ 4606.029645] [<ffffffff821fb6f0>] ? SyS_socketpair+0x470/0x470
> >> > [ 4606.036154] [<ffffffff821fb6fe>] SyS_bind+0xe/0x10
> >> > [ 4606.041595] [<ffffffff81007b56>] do_syscall_64+0x1a6/0x500
> >> > [ 4606.047813] [<ffffffff8100401a>] ? trace_hardirqs_on_thunk+0x1a/0x1c
> >> > [ 4606.055000] [<ffffffff8269e6bf>] entry_SYSCALL64_slow_path+0x25/0x25
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-08-31 19:37 ` possible circular locking dependency detected (bisected) CAI Qian
2016-08-31 20:16 ` Rainer Weikusat
2016-09-01 19:14 ` CAI Qian
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