From: CAI Qian <caiqian@redhat.com>
To: tj <tj@kernel.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Dave Chinner <david@fromorbit.com>,
linux-xfs <linux-xfs@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>, Nick Piggin <npiggin@gmail.com>,
linux-fsdevel@vger.kernel.org
Subject: Re: local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked)
Date: Wed, 5 Oct 2016 14:57:04 -0400 (EDT) [thread overview]
Message-ID: <874538236.682217.1475693824077.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <270577901.647921.1475682888765.JavaMail.zimbra@redhat.com>
----- Original Message -----
> From: "CAI Qian" <caiqian@redhat.com>
> To: "tj" <tj@kernel.org>
> Cc: "Al Viro" <viro@ZenIV.linux.org.uk>, "Linus Torvalds" <torvalds@linux-foundation.org>, "Dave Chinner"
> <david@fromorbit.com>, "linux-xfs" <linux-xfs@vger.kernel.org>, "Jens Axboe" <axboe@kernel.dk>, "Nick Piggin"
> <npiggin@gmail.com>, linux-fsdevel@vger.kernel.org
> Sent: Wednesday, October 5, 2016 11:54:48 AM
> Subject: Re: local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked)
>
>
>
> ----- Original Message -----
> > From: "tj" <tj@kernel.org>
> > To: "CAI Qian" <caiqian@redhat.com>
> > Cc: "Al Viro" <viro@ZenIV.linux.org.uk>, "Linus Torvalds"
> > <torvalds@linux-foundation.org>, "Dave Chinner"
> > <david@fromorbit.com>, "linux-xfs" <linux-xfs@vger.kernel.org>, "Jens
> > Axboe" <axboe@kernel.dk>, "Nick Piggin"
> > <npiggin@gmail.com>, linux-fsdevel@vger.kernel.org
> > Sent: Wednesday, October 5, 2016 11:30:14 AM
> > Subject: Re: local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT]
> > splice_read reworked)
> >
> > Hello, CAI.
> >
> > On Wed, Oct 05, 2016 at 10:09:39AM -0400, CAI Qian wrote:
> > > > This one seems to be the offender. cgroup is trying to offline a
> > > > cpuset css, which takes place under cgroup_mutex. The offlining ends
> > > > up trying to drain active usages of a sysctl table which apprently is
> > > > not happening. Did something hang or crash while trying to generate
> > > > sysctl content?
> > >
> > > Hmm, I am not sure, since the trinity was running from an non-privileged
> > > user which can only read content from /proc or /sys.
> >
> > So, userland, priviledged or not, can't cause this. The ref is held
> > only while the kernel code is operating to generate content or
> > iterating, which shouldn't be affected by userland actions. This is
> > caused by kernel code hanging or crashing while holding a ref.
> Right, the trinity calls many different random syscalls and options on those
> /proc/ and /sys/ files and generate lots of different errno. It is likely
> some of error-path out there causes hang or crash.
Tejun,
Not sure if this related, and there is always a lockdep regards procfs happened
below unless masking by other lockdep issues before the cgroup hang. Also, this
hang is always reproducible.
[ 4787.875980]
[ 4787.877645] ======================================================
[ 4787.884540] [ INFO: possible circular locking dependency detected ]
[ 4787.891533] 4.8.0-rc8-usrns-scale+ #8 Tainted: G W
[ 4787.898138] -------------------------------------------------------
[ 4787.905130] trinity-c116/106905 is trying to acquire lock:
[ 4787.911251] (&p->lock){+.+.+.}, at: [<ffffffff812aca8c>] seq_read+0x4c/0x3e0
[ 4787.919264]
[ 4787.919264] but task is already holding lock:
[ 4787.925773] (sb_writers#8){.+.+.+}, at: [<ffffffff81284367>] __sb_start_write+0xb7/0xf0
[ 4787.934854]
[ 4787.934854] which lock already depends on the new lock.
[ 4787.934854]
[ 4787.943981]
[ 4787.943981] the existing dependency chain (in reverse order) is:
[ 4787.952333]
-> #3 (sb_writers#8){.+.+.+}:
[ 4787.957050] [<ffffffff810fd711>] __lock_acquire+0x3f1/0x7f0
[ 4787.963960] [<ffffffff810fe166>] lock_acquire+0xd6/0x240
[ 4787.970577] [<ffffffff810f769a>] percpu_down_read+0x4a/0xa0
[ 4787.977487] [<ffffffff81284367>] __sb_start_write+0xb7/0xf0
[ 4787.984395] [<ffffffff812a8974>] mnt_want_write+0x24/0x50
[ 4787.991110] [<ffffffffa05049af>] ovl_want_write+0x1f/0x30 [overlay]
[ 4787.998799] [<ffffffffa05070c2>] ovl_do_remove+0x42/0x4a0 [overlay]
[ 4788.006483] [<ffffffffa0507536>] ovl_rmdir+0x16/0x20 [overlay]
[ 4788.013682] [<ffffffff8128d357>] vfs_rmdir+0xb7/0x130
[ 4788.020009] [<ffffffff81292ed3>] do_rmdir+0x183/0x1f0
[ 4788.026335] [<ffffffff81293cf2>] SyS_unlinkat+0x22/0x30
[ 4788.032853] [<ffffffff81003f8c>] do_syscall_64+0x6c/0x1e0
[ 4788.039576] [<ffffffff817d927f>] return_from_SYSCALL_64+0x0/0x7a
[ 4788.046962]
-> #2 (&sb->s_type->i_mutex_key#16){++++++}:
[ 4788.053140] [<ffffffff810fd711>] __lock_acquire+0x3f1/0x7f0
[ 4788.060049] [<ffffffff810fe166>] lock_acquire+0xd6/0x240
[ 4788.066664] [<ffffffff817d60e7>] down_read+0x47/0x70
[ 4788.072893] [<ffffffff8128ce79>] lookup_slow+0xc9/0x200
[ 4788.079410] [<ffffffff81290b9c>] walk_component+0x1ec/0x310
[ 4788.086315] [<ffffffff81290e5f>] link_path_walk+0x19f/0x5f0
[ 4788.093219] [<ffffffff8129151d>] path_openat+0xdd/0xb80
[ 4788.099748] [<ffffffff81293511>] do_filp_open+0x91/0x100
[ 4788.106362] [<ffffffff81286f56>] do_open_execat+0x76/0x180
[ 4788.113186] [<ffffffff8128747b>] open_exec+0x2b/0x50
[ 4788.119404] [<ffffffff812ec61d>] load_elf_binary+0x28d/0x1120
[ 4788.126511] [<ffffffff81288487>] search_binary_handler+0x97/0x1c0
[ 4788.134002] [<ffffffff81289619>] do_execveat_common.isra.36+0x6a9/0x9f0
[ 4788.142071] [<ffffffff81289c4a>] SyS_execve+0x3a/0x50
[ 4788.148398] [<ffffffff81003f8c>] do_syscall_64+0x6c/0x1e0
[ 4788.155110] [<ffffffff817d927f>] return_from_SYSCALL_64+0x0/0x7a
[ 4788.162502]
-> #1 (&sig->cred_guard_mutex){+.+.+.}:
[ 4788.168179] [<ffffffff810fd711>] __lock_acquire+0x3f1/0x7f0
[ 4788.175085] [<ffffffff810fe166>] lock_acquire+0xd6/0x240
[ 4788.181712] [<ffffffff817d4557>] mutex_lock_killable_nested+0x87/0x500
[ 4788.189695] [<ffffffff81099599>] mm_access+0x29/0xa0
[ 4788.195924] [<ffffffff81302b6c>] proc_pid_auxv+0x1c/0x70
[ 4788.202540] [<ffffffff813039d0>] proc_single_show+0x50/0x90
[ 4788.209445] [<ffffffff812acb48>] seq_read+0x108/0x3e0
[ 4788.215774] [<ffffffff8127fb07>] __vfs_read+0x37/0x150
[ 4788.222198] [<ffffffff81280d35>] vfs_read+0x95/0x140
[ 4788.228425] [<ffffffff81282268>] SyS_read+0x58/0xc0
[ 4788.234557] [<ffffffff81003f8c>] do_syscall_64+0x6c/0x1e0
[ 4788.241268] [<ffffffff817d927f>] return_from_SYSCALL_64+0x0/0x7a
[ 4788.248660]
-> #0 (&p->lock){+.+.+.}:
[ 4788.252987] [<ffffffff810fc062>] validate_chain.isra.37+0xe72/0x1150
[ 4788.260769] [<ffffffff810fd711>] __lock_acquire+0x3f1/0x7f0
[ 4788.267676] [<ffffffff810fe166>] lock_acquire+0xd6/0x240
[ 4788.274302] [<ffffffff817d3807>] mutex_lock_nested+0x77/0x430
[ 4788.281406] [<ffffffff812aca8c>] seq_read+0x4c/0x3e0
[ 4788.287633] [<ffffffff81316b39>] kernfs_fop_read+0x129/0x1b0
[ 4788.294659] [<ffffffff8127fca3>] do_loop_readv_writev+0x83/0xc0
[ 4788.301954] [<ffffffff812811a8>] do_readv_writev+0x218/0x240
[ 4788.308959] [<ffffffff81281209>] vfs_readv+0x39/0x50
[ 4788.315188] [<ffffffff812bc6b1>] default_file_splice_read+0x1a1/0x2b0
[ 4788.323070] [<ffffffff812bc206>] do_splice_to+0x76/0x90
[ 4788.329587] [<ffffffff812bc2db>] splice_direct_to_actor+0xbb/0x220
[ 4788.337173] [<ffffffff812bc4d8>] do_splice_direct+0x98/0xd0
[ 4788.344078] [<ffffffff81281dd1>] do_sendfile+0x1d1/0x3b0
[ 4788.350694] [<ffffffff812829c9>] SyS_sendfile64+0xc9/0xd0
[ 4788.357405] [<ffffffff81003f8c>] do_syscall_64+0x6c/0x1e0
[ 4788.364119] [<ffffffff817d927f>] return_from_SYSCALL_64+0x0/0x7a
[ 4788.371511]
[ 4788.371511] other info that might help us debug this:
[ 4788.371511]
[ 4788.380443] Chain exists of:
&p->lock --> &sb->s_type->i_mutex_key#16 --> sb_writers#8
[ 4788.389881] Possible unsafe locking scenario:
[ 4788.389881]
[ 4788.396497] CPU0 CPU1
[ 4788.401549] ---- ----
[ 4788.406614] lock(sb_writers#8);
[ 4788.410352] lock(&sb->s_type->i_mutex_key#16);
[ 4788.418354] lock(sb_writers#8);
[ 4788.424902] lock(&p->lock);
[ 4788.428229]
[ 4788.428229] *** DEADLOCK ***
[ 4788.428229]
[ 4788.434836] 1 lock held by trinity-c116/106905:
[ 4788.439888] #0: (sb_writers#8){.+.+.+}, at: [<ffffffff81284367>] __sb_start_write+0xb7/0xf0
[ 4788.449473]
[ 4788.449473] stack backtrace:
[ 4788.454334] CPU: 16 PID: 106905 Comm: trinity-c116 Tainted: G W 4.8.0-rc8-usrns-scale+ #8
[ 4788.464719] Hardware name: Intel Corporation S2600WTT/S2600WTT, BIOS GRNDSDP1.86B.0044.R00.1501191641 01/19/2015
[ 4788.476076] 0000000000000086 00000000cbfc6314 ffff8803ce78b760 ffffffff813d5e93
[ 4788.484371] ffffffff82a3fbd0 ffffffff82a94890 ffff8803ce78b7a0 ffffffff810fa6ec
[ 4788.492663] ffff8803ce78b7e0 ffff8802ead08000 0000000000000001 ffff8802ead08ca0
[ 4788.500966] Call Trace:
[ 4788.503694] [<ffffffff813d5e93>] dump_stack+0x85/0xc2
[ 4788.509426] [<ffffffff810fa6ec>] print_circular_bug+0x1ec/0x260
[ 4788.516128] [<ffffffff810fc062>] validate_chain.isra.37+0xe72/0x1150
[ 4788.523319] [<ffffffff811d4491>] ? ___perf_sw_event+0x171/0x290
[ 4788.530022] [<ffffffff810fd711>] __lock_acquire+0x3f1/0x7f0
[ 4788.536335] [<ffffffff810fe166>] lock_acquire+0xd6/0x240
[ 4788.542359] [<ffffffff812aca8c>] ? seq_read+0x4c/0x3e0
[ 4788.548188] [<ffffffff812aca8c>] ? seq_read+0x4c/0x3e0
[ 4788.554019] [<ffffffff817d3807>] mutex_lock_nested+0x77/0x430
[ 4788.560528] [<ffffffff812aca8c>] ? seq_read+0x4c/0x3e0
[ 4788.566358] [<ffffffff812aca8c>] seq_read+0x4c/0x3e0
[ 4788.571995] [<ffffffff81316a10>] ? kernfs_fop_open+0x3a0/0x3a0
[ 4788.578600] [<ffffffff81316b39>] kernfs_fop_read+0x129/0x1b0
[ 4788.585012] [<ffffffff81316a10>] ? kernfs_fop_open+0x3a0/0x3a0
[ 4788.591617] [<ffffffff8127fca3>] do_loop_readv_writev+0x83/0xc0
[ 4788.598318] [<ffffffff81316a10>] ? kernfs_fop_open+0x3a0/0x3a0
[ 4788.604924] [<ffffffff812811a8>] do_readv_writev+0x218/0x240
[ 4788.611347] [<ffffffff813e9535>] ? push_pipe+0xd5/0x190
[ 4788.617278] [<ffffffff813ecec0>] ? iov_iter_get_pages_alloc+0x250/0x400
[ 4788.624746] [<ffffffff81281209>] vfs_readv+0x39/0x50
[ 4788.630381] [<ffffffff812bc6b1>] default_file_splice_read+0x1a1/0x2b0
[ 4788.637668] [<ffffffff8134ae20>] ? security_file_permission+0xa0/0xc0
[ 4788.644954] [<ffffffff812bc206>] do_splice_to+0x76/0x90
[ 4788.650880] [<ffffffff812bc2db>] splice_direct_to_actor+0xbb/0x220
[ 4788.657872] [<ffffffff812bba80>] ? generic_pipe_buf_nosteal+0x10/0x10
[ 4788.665157] [<ffffffff812bc4d8>] do_splice_direct+0x98/0xd0
[ 4788.671472] [<ffffffff81281dd1>] do_sendfile+0x1d1/0x3b0
[ 4788.677499] [<ffffffff812829c9>] SyS_sendfile64+0xc9/0xd0
[ 4788.683622] [<ffffffff81003f8c>] do_syscall_64+0x6c/0x1e0
[ 4788.689744] [<ffffffff817d927f>] entry_SYSCALL64_slow_path+0x25/0x25
next prev parent reply other threads:[~2016-10-05 18:57 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20160908235521.GL2356@ZenIV.linux.org.uk>
[not found] ` <20160909015324.GD30056@dastard>
[not found] ` <CA+55aFzohsUXj_3BeFNr2t50Wm=G+7toRDEz=Tk7VJqP3n1hXQ@mail.gmail.com>
[not found] ` <CA+55aFxrqCng2Qxasc9pyMrKUGFjo==fEaFT1vkH9Lncte3RgQ@mail.gmail.com>
[not found] ` <20160909023452.GO2356@ZenIV.linux.org.uk>
[not found] ` <CA+55aFwHQMjO4-vtfB9-ytc=o+DRo-HXVGckvXLboUxgpwb7_g@mail.gmail.com>
[not found] ` <20160909221945.GQ2356@ZenIV.linux.org.uk>
[not found] ` <CA+55aFzTOOB6oEVaaGD0N7Uznk-W9+ULPwzsxS_L_oZqGVSeLA@mail.gmail.com>
[not found] ` <20160914031648.GB2356@ZenIV.linux.org.uk>
[not found] ` <20160914133925.2fba4629@roar.ozlabs.ibm.com>
2016-09-18 5:33 ` xfs_file_splice_read: possible circular locking dependency detected Al Viro
2016-09-19 3:08 ` Nicholas Piggin
2016-09-19 6:11 ` Al Viro
2016-09-19 7:26 ` Nicholas Piggin
[not found] ` <CA+55aFznQaOWoSMNphgGJJWZ=8-odrc0DAUMzfGPQe+_N4UgNA@mail.gmail.com>
[not found] ` <20160914042559.GC2356@ZenIV.linux.org.uk>
[not found] ` <20160917082007.GA6489@ZenIV.linux.org.uk>
[not found] ` <20160917190023.GA8039@ZenIV.linux.org.uk>
2016-09-18 19:31 ` skb_splice_bits() and large chunks in pipe (was " Al Viro
2016-09-18 20:12 ` Linus Torvalds
2016-09-18 22:31 ` Al Viro
2016-09-19 0:18 ` Linus Torvalds
2016-09-19 0:22 ` Al Viro
2016-09-20 9:51 ` Herbert Xu
2016-09-23 19:00 ` [RFC][CFT] splice_read reworked Al Viro
2016-09-23 19:01 ` [PATCH 01/11] fix memory leaks in tracing_buffers_splice_read() Al Viro
2016-09-23 19:02 ` [PATCH 02/11] splice_to_pipe(): don't open-code wakeup_pipe_readers() Al Viro
2016-09-23 19:02 ` [PATCH 03/11] splice: switch get_iovec_page_array() to iov_iter Al Viro
2016-09-23 19:03 ` [PATCH 04/11] splice: lift pipe_lock out of splice_to_pipe() Al Viro
2016-09-23 19:45 ` Linus Torvalds
2016-09-23 20:10 ` Al Viro
2016-09-23 20:36 ` Linus Torvalds
2016-09-24 3:59 ` Al Viro
2016-09-24 17:29 ` Al Viro
2016-09-27 15:38 ` Nicholas Piggin
2016-09-27 15:53 ` Chuck Lever
2016-09-24 3:59 ` [PATCH 04/12] " Al Viro
2016-09-26 13:35 ` Miklos Szeredi
2016-09-27 4:14 ` Al Viro
2016-12-17 19:54 ` Andreas Schwab
2016-12-18 19:28 ` Linus Torvalds
2016-12-18 19:57 ` Andreas Schwab
2016-12-18 20:12 ` Al Viro
2016-12-18 20:30 ` Al Viro
2016-12-18 22:10 ` Linus Torvalds
2016-12-18 22:18 ` Al Viro
2016-12-18 22:22 ` Linus Torvalds
2016-12-18 22:49 ` Andreas Schwab
2016-12-21 18:56 ` Andreas Schwab
2016-12-21 19:12 ` Linus Torvalds
2016-09-24 4:00 ` [PATCH 06/12] new helper: add_to_pipe() Al Viro
2016-09-26 13:49 ` Miklos Szeredi
2016-09-24 4:01 ` [PATCH 10/12] new iov_iter flavour: pipe-backed Al Viro
2016-09-29 20:53 ` Miklos Szeredi
2016-09-29 22:50 ` Al Viro
2016-09-30 7:30 ` Miklos Szeredi
2016-10-03 3:34 ` [RFC] O_DIRECT vs EFAULT (was Re: [PATCH 10/12] new iov_iter flavour: pipe-backed) Al Viro
2016-10-03 17:07 ` Linus Torvalds
2016-10-03 18:54 ` Al Viro
2016-09-24 4:01 ` [PATCH 11/12] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-24 4:02 ` [PATCH 12/12] switch default_file_splice_read() to use of pipe-backed iov_iter Al Viro
2016-09-23 19:03 ` [PATCH 05/11] skb_splice_bits(): get rid of callback Al Viro
2016-09-23 19:04 ` [PATCH 06/11] new helper: add_to_pipe() Al Viro
2016-09-23 19:04 ` [PATCH 07/11] fuse_dev_splice_read(): switch to add_to_pipe() Al Viro
2016-09-23 19:06 ` [PATCH 08/11] cifs: don't use memcpy() to copy struct iov_iter Al Viro
2016-09-23 19:08 ` [PATCH 09/11] fuse_ioctl_copy_user(): don't open-code copy_page_{to,from}_iter() Al Viro
2016-09-26 9:31 ` Miklos Szeredi
2016-09-23 19:09 ` [PATCH 10/11] new iov_iter flavour: pipe-backed Al Viro
2016-09-23 19:10 ` [PATCH 11/11] switch generic_file_splice_read() to use of ->read_iter() Al Viro
2016-09-30 13:32 ` [RFC][CFT] splice_read reworked CAI Qian
2016-09-30 17:42 ` CAI Qian
2016-09-30 18:33 ` CAI Qian
2016-10-03 1:37 ` Al Viro
2016-10-03 17:49 ` CAI Qian
2016-10-04 17:39 ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) CAI Qian
2016-10-04 21:42 ` tj
2016-10-05 14:09 ` CAI Qian
2016-10-05 15:30 ` tj
2016-10-05 15:54 ` CAI Qian
2016-10-05 18:57 ` CAI Qian [this message]
2016-10-05 20:05 ` Al Viro
2016-10-06 12:20 ` CAI Qian
2016-10-06 12:25 ` CAI Qian
2016-10-06 16:11 ` CAI Qian
2016-10-06 17:00 ` Linus Torvalds
2016-10-06 18:12 ` CAI Qian
2016-10-07 9:57 ` Dave Chinner
2016-10-07 15:25 ` Linus Torvalds
2016-10-07 7:08 ` Jan Kara
2016-10-07 14:43 ` CAI Qian
2016-10-07 15:27 ` CAI Qian
2016-10-07 18:56 ` CAI Qian
2016-10-09 21:54 ` Dave Chinner
2016-10-10 14:10 ` CAI Qian
2016-10-10 20:14 ` CAI Qian
2016-10-10 21:57 ` Dave Chinner
2016-10-12 19:50 ` [bisected] " CAI Qian
2016-10-12 20:59 ` Dave Chinner
2016-10-13 16:25 ` CAI Qian
2016-10-13 20:49 ` Dave Chinner
2016-10-13 20:56 ` CAI Qian
2016-10-09 21:51 ` Dave Chinner
2016-10-21 15:38 ` [4.9-rc1+] overlayfs lockdep CAI Qian
2016-10-24 12:57 ` Miklos Szeredi
2016-10-07 9:27 ` local DoS - systemd hang or timeout (WAS: Re: [RFC][CFT] splice_read reworked) Dave Chinner
2016-10-03 1:42 ` [RFC][CFT] splice_read reworked Al Viro
2016-10-03 14:06 ` CAI Qian
2016-10-03 15:20 ` CAI Qian
2016-10-03 21:12 ` Dave Chinner
2016-10-04 13:57 ` CAI Qian
2016-10-03 20:32 ` CAI Qian
2016-10-03 20:35 ` Al Viro
2016-10-04 13:29 ` CAI Qian
2016-10-04 14:28 ` Al Viro
2016-10-04 16:21 ` CAI Qian
2016-10-04 20:12 ` Al Viro
2016-10-05 14:30 ` CAI Qian
2016-10-05 16:07 ` Al Viro
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