Zhou Chengming b9d6631395 sysctl: Drop reference added by grab_header in proc_sys_readdir ... commit 93362fa47fe98b62e4a34ab408c4a418432e7939 upstream. Fixes CVE-2016-9191, proc_sys_readdir doesn't drop reference added by grab_header when return from !dir_emit_dots path. It can cause any path called unregister_sysctl_table will wait forever. The calltrace of CVE-2016-9191: [ 5535.960522] Call Trace: [ 5535.963265] [<ffffffff817cdaaf>] schedule+0x3f/0xa0 [ 5535.968817] [<ffffffff817d33fb>] schedule_timeout+0x3db/0x6f0 [ 5535.975346] [<ffffffff817cf055>] ? wait_for_completion+0x45/0x130 [ 5535.982256] [<ffffffff817cf0d3>] wait_for_completion+0xc3/0x130 [ 5535.988972] [<ffffffff810d1fd0>] ? wake_up_q+0x80/0x80 [ 5535.994804] [<ffffffff8130de64>] drop_sysctl_table+0xc4/0xe0 [ 5536.001227] [<ffffffff8130de17>] drop_sysctl_table+0x77/0xe0 [ 5536.007648] [<ffffffff8130decd>] unregister_sysctl_table+0x4d/0xa0 [ 5536.014654] [<ffffffff8130deff>] unregister_sysctl_table+0x7f/0xa0 [ 5536.021657] [<ffffffff810f57f5>] unregister_sched_domain_sysctl+0x15/0x40 [ 5536.029344] [<ffffffff810d7704>] partition_sched_domains+0x44/0x450 [ 5536.036447] [<ffffffff817d0761>] ? __mutex_unlock_slowpath+0x111/0x1f0 [ 5536.043844] [<ffffffff81167684>] rebuild_sched_domains_locked+0x64/0xb0 [ 5536.051336] [<ffffffff8116789d>] update_flag+0x11d/0x210 [ 5536.057373] [<ffffffff817cf61f>] ? mutex_lock_nested+0x2df/0x450 [ 5536.064186] [<ffffffff81167acb>] ? cpuset_css_offline+0x1b/0x60 [ 5536.070899] [<ffffffff810fce3d>] ? trace_hardirqs_on+0xd/0x10 [ 5536.077420] [<ffffffff817cf61f>] ? mutex_lock_nested+0x2df/0x450 [ 5536.084234] [<ffffffff8115a9f5>] ? css_killed_work_fn+0x25/0x220 [ 5536.091049] [<ffffffff81167ae5>] cpuset_css_offline+0x35/0x60 [ 5536.097571] [<ffffffff8115aa2c>] css_killed_work_fn+0x5c/0x220 [ 5536.104207] [<ffffffff810bc83f>] process_one_work+0x1df/0x710 [ 5536.110736] [<ffffffff810bc7c0>] ? process_one_work+0x160/0x710 [ 5536.117461] [<ffffffff810bce9b>] worker_thread+0x12b/0x4a0 [ 5536.123697] [<ffffffff810bcd70>] ? process_one_work+0x710/0x710 [ 5536.130426] [<ffffffff810c3f7e>] kthread+0xfe/0x120 [ 5536.135991] [<ffffffff817d4baf>] ret_from_fork+0x1f/0x40 [ 5536.142041] [<ffffffff810c3e80>] ? kthread_create_on_node+0x230/0x230 One cgroup maintainer mentioned that "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." The real reason is that proc_sys_readdir doesn't drop reference added by grab_header when return from !dir_emit_dots path. So this cpuset offline path will wait here forever. See here for details: http://www.openwall.com/lists/oss-security/2016/11/04/13 Fixes: f0c3b5093a ("[readdir] convert procfs") Reported-by: CAI Qian <caiqian@redhat.com> Tested-by: Yang Shukui <yangshukui@huawei.com> Signed-off-by: Zhou Chengming <zhouchengming1@huawei.com> Acked-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2017-01-19 20:17:21 +01:00
..
array.c	ptrace: use fsuid, fsgid, effective creds for fs access checks	2016-02-25 12:01:16 -08:00
base.c	mm: introduce get_task_exe_file	2016-09-24 10:07:36 +02:00
cmdline.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
consoles.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
cpuinfo.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
devices.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
fd.c	proc: actually make proc_fd_permission() thread-friendly	2015-11-06 17:50:42 -08:00
fd.h	proc: Move proc_fd() to fs/proc/fd.h	2013-05-01 17:29:39 -04:00
generic.c	proc: change proc_subdir_lock to a rwlock	2015-09-10 13:29:01 -07:00
inode.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2015-07-03 15:20:57 -07:00
internal.h	proc: Allow creating permanently empty directories that serve as mount points	2015-07-01 10:36:41 -05:00
interrupts.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
Kconfig	fs, proc: add help for CONFIG_PROC_CHILDREN	2015-07-17 16:39:52 -07:00
kcore.c	x86/fpu, sched: Introduce CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT and use it on x86	2015-07-18 03:42:51 +02:00
kmsg.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
loadavg.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
Makefile	proc: Implement /proc/thread-self to point at the directory of the current thread	2014-08-04 10:07:11 -07:00
meminfo.c	mm: get rid of 'vmalloc_info' from /proc/meminfo	2015-11-01 17:09:15 -08:00
namespaces.c	ptrace: use fsuid, fsgid, effective creds for fs access checks	2016-02-25 12:01:16 -08:00
nommu.c	vfs: add seq_file_path() helper	2015-06-23 18:01:07 -04:00
page.c	proc: add cond_resched to /proc/kpage* read/write loop	2015-09-10 13:29:01 -07:00
proc_net.c	VFS: normal filesystems (and lustre): d_inode() annotations	2015-04-15 15:06:57 -04:00
proc_sysctl.c	sysctl: Drop reference added by grab_header in proc_sys_readdir	2017-01-19 20:17:21 +01:00
proc_tty.c	proc: remove proc_tty_ldisc variable	2014-08-08 15:57:22 -07:00
root.c	proc: prevent stacking filesystems on top	2016-06-24 10:18:20 -07:00
self.c	don't pass nameidata to ->follow_link()	2015-05-10 22:20:15 -04:00
softirqs.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
stat.c	genirq: Prevent proc race against freeing of irq descriptors	2014-12-13 13:33:07 +01:00
task_mmu.c	proc: revert /proc/<pid>/maps [stack:TID] annotation	2016-09-15 08:27:46 +02:00
task_nommu.c	proc: revert /proc/<pid>/maps [stack:TID] annotation	2016-09-15 08:27:46 +02:00
thread_self.c	don't pass nameidata to ->follow_link()	2015-05-10 22:20:15 -04:00
uptime.c	cputime: Default implementation of nsecs -> cputime conversion	2014-03-13 15:56:43 +01:00
version.c	fs/proc: don't use module_init for non-modular core code	2014-01-23 16:37:02 -08:00
vmcore.c	vmcore: fix PT_NOTE n_namesz, n_descsz overflow issue	2015-02-17 14:34:52 -08:00