From mboxrd@z Thu Jan 1 00:00:00 1970 From: CAI Qian Subject: Re: possible circular locking dependency detected (bisected) Date: Wed, 31 Aug 2016 15:37:37 -0400 (EDT) Message-ID: <1934642616.820579.1472672257777.JavaMail.zimbra@redhat.com> References: <1018744655.2694243.1472223057200.JavaMail.zimbra@redhat.com> <812527981.484636.1472591145655.JavaMail.zimbra@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Miklos Szeredi , Eric Sandeen , Network Development To: Rainer Weikusat , security@kernel.org Return-path: Received: from mx6-phx2.redhat.com ([209.132.183.39]:59008 "EHLO mx6-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753048AbcHaThv (ORCPT ); Wed, 31 Aug 2016 15:37:51 -0400 In-Reply-To: <812527981.484636.1472591145655.JavaMail.zimbra@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Reverted the patch below fixes this problem. c845acb324aa85a39650a14e7696982ceea75dc1 af_unix: Fix splice-bind deadlock CAI Qian ----- Original Message ----- > From: "CAI Qian" > To: security@kernel.org > Cc: "Miklos Szeredi" , "Eric Sandeen" > 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" > > 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: [] > > __sb_start_write+0xb4/0xf0 > > [ 4605.460642] > > [ 4605.460642] but task is already holding lock: > > [ 4605.467150] (&u->readlock){+.+.+.}, at: [] > > 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] [] lock_acquire+0x1fa/0x440 > > [ 4605.504659] [] > > mutex_lock_interruptible_nested+0xdd/0x920 > > [ 4605.513119] [] unix_bind+0x299/0xdf0 > > [ 4605.519540] [] SYSC_bind+0x1d8/0x240 > > [ 4605.525964] [] SyS_bind+0xe/0x10 > > [ 4605.531998] [] do_syscall_64+0x1a6/0x500 > > [ 4605.538811] [] return_from_SYSCALL_64+0x0/0x7a > > [ 4605.546203] > > [ 4605.546203] -> #1 (&type->i_mutex_dir_key#3/1){+.+.+.}: > > [ 4605.552292] [] lock_acquire+0x1fa/0x440 > > [ 4605.559002] [] down_write_nested+0x5e/0xe0 > > [ 4605.566008] [] filename_create+0x155/0x470 > > [ 4605.573013] [] SyS_mkdir+0xaf/0x1f0 > > [ 4605.579339] [] > > entry_SYSCALL_64_fastpath+0x1f/0xbd > > [ 4605.587119] > > [ 4605.587119] -> #0 (sb_writers#8){.+.+.+}: > > [ 4605.591835] [] __lock_acquire+0x3043/0x3dd0 > > [ 4605.598935] [] lock_acquire+0x1fa/0x440 > > [ 4605.605646] [] percpu_down_read+0x4f/0xa0 > > [ 4605.612552] [] __sb_start_write+0xb4/0xf0 > > [ 4605.619459] [] mnt_want_write+0x41/0xb0 > > [ 4605.626173] [] ovl_want_write+0x76/0xa0 > > [overlay] > > [ 4605.633860] [] ovl_create_object+0xa3/0x2d0 > > [overlay] > > [ 4605.641942] [] ovl_mknod+0x31/0x40 [overlay] > > [ 4605.649138] [] vfs_mknod+0x34b/0x560 > > [ 4605.655570] [] unix_bind+0x4ca/0xdf0 > > [ 4605.661991] [] SYSC_bind+0x1d8/0x240 > > [ 4605.668412] [] SyS_bind+0xe/0x10 > > [ 4605.674456] [] do_syscall_64+0x1a6/0x500 > > [ 4605.681266] [] 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: [] > > __sb_start_write+0xb4/0xf0 > > [ 4605.766930] #1: (&sb->s_type->i_mutex_key#16/1){+.+.+.}, at: > > [] filename_create+0x155/0x470 > > [ 4605.778269] #2: (&u->readlock){+.+.+.}, at: [] > > 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] [] dump_stack+0x85/0xc4 > > [ 4605.844390] [] print_circular_bug+0x356/0x460 > > [ 4605.851092] [] __lock_acquire+0x3043/0x3dd0 > > [ 4605.857602] [] ? kfree+0x310/0x370 > > [ 4605.863238] [] ? > > debug_check_no_locks_freed+0x2c0/0x2c0 > > [ 4605.870912] [] ? avc_has_perm+0xa2/0x480 > > [ 4605.877130] [] ? avc_has_perm+0x242/0x480 > > [ 4605.883443] [] ? avc_has_perm+0x261/0x480 > > [ 4605.889758] [] ? avc_has_perm+0xa2/0x480 > > [ 4605.895977] [] lock_acquire+0x1fa/0x440 > > [ 4605.902098] [] ? __sb_start_write+0xb4/0xf0 > > [ 4605.908607] [] percpu_down_read+0x4f/0xa0 > > [ 4605.914921] [] ? __sb_start_write+0xb4/0xf0 > > [ 4605.921429] [] __sb_start_write+0xb4/0xf0 > > [ 4605.927742] [] mnt_want_write+0x41/0xb0 > > [ 4605.933875] [] ovl_want_write+0x76/0xa0 [overlay] > > [ 4605.940967] [] ovl_create_object+0xa3/0x2d0 [overlay] > > [ 4605.948445] [] ? > > ovl_create_or_link.part.3+0xc70/0xc70 > > [overlay] > > [ 4605.956990] [] ? selinux_inode_mknod+0x42/0x80 > > [ 4605.963790] [] ovl_mknod+0x31/0x40 [overlay] > > [ 4605.970395] [] vfs_mknod+0x34b/0x560 > > [ 4605.976224] [] unix_bind+0x4ca/0xdf0 > > [ 4605.982053] [] ? unix_autobind.isra.24+0x600/0x600 > > [ 4605.989244] [] ? __might_fault+0xf6/0x1b0 > > [ 4605.995550] [] SYSC_bind+0x1d8/0x240 > > [ 4606.001381] [] ? > > move_addr_to_kernel.part.13+0xe0/0xe0 > > [ 4606.008958] [] ? __audit_syscall_entry+0x325/0x6f0 > > [ 4606.016144] [] ? __audit_syscall_entry+0x325/0x6f0 > > [ 4606.023332] [] ? do_syscall_64+0x52/0x500 > > [ 4606.029645] [] ? SyS_socketpair+0x470/0x470 > > [ 4606.036154] [] SyS_bind+0xe/0x10 > > [ 4606.041595] [] do_syscall_64+0x1a6/0x500 > > [ 4606.047813] [] ? trace_hardirqs_on_thunk+0x1a/0x1c > > [ 4606.055000] [] entry_SYSCALL64_slow_path+0x25/0x25