[linux] 01/02: sysctl: Drop reference added by grab_header in proc_sys_readdir (CVE-2016-9191)
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Mon Jan 16 09:11:21 UTC 2017
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commit a126d0bd2708ca40b91b5c2b2ab05189475aa5fd
Author: Salvatore Bonaccorso <carnil at debian.org>
Date: Mon Jan 16 09:25:25 2017 +0100
sysctl: Drop reference added by grab_header in proc_sys_readdir (CVE-2016-9191)
---
debian/changelog | 6 +-
...-reference-added-by-grab_header-in-proc_s.patch | 87 ++++++++++++++++++++++
debian/patches/series | 1 +
3 files changed, 93 insertions(+), 1 deletion(-)
diff --git a/debian/changelog b/debian/changelog
index 2020c30..cfcca67 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -239,7 +239,11 @@ linux (4.9.4-1) UNRELEASED; urgency=medium
support (Closes: #851481)
* nbd: use loff_t for blocksize and nbd_set_size args (Closes: #851533)
- -- Salvatore Bonaccorso <carnil at debian.org> Sun, 15 Jan 2017 14:48:41 +0100
+ [ Salvatore Bonaccorso ]
+ * sysctl: Drop reference added by grab_header in proc_sys_readdir
+ (CVE-2016-9191)
+
+ -- Salvatore Bonaccorso <carnil at debian.org> Mon, 16 Jan 2017 09:26:13 +0100
linux (4.9.2-2) unstable; urgency=medium
diff --git a/debian/patches/bugfix/all/sysctl-Drop-reference-added-by-grab_header-in-proc_s.patch b/debian/patches/bugfix/all/sysctl-Drop-reference-added-by-grab_header-in-proc_s.patch
new file mode 100644
index 0000000..c91cd09
--- /dev/null
+++ b/debian/patches/bugfix/all/sysctl-Drop-reference-added-by-grab_header-in-proc_s.patch
@@ -0,0 +1,87 @@
+From: Zhou Chengming <zhouchengming1 at huawei.com>
+Date: Fri, 6 Jan 2017 09:32:32 +0800
+Subject: sysctl: Drop reference added by grab_header in proc_sys_readdir
+Origin: https://git.kernel.org/linus/93362fa47fe98b62e4a34ab408c4a418432e7939
+
+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: f0c3b5093add ("[readdir] convert procfs")
+Cc: stable at vger.kernel.org
+Reported-by: CAI Qian <caiqian at redhat.com>
+Tested-by: Yang Shukui <yangshukui at huawei.com>
+Signed-off-by: Zhou Chengming <zhouchengming1 at huawei.com>
+Acked-by: Al Viro <viro at ZenIV.linux.org.uk>
+Signed-off-by: Eric W. Biederman <ebiederm at xmission.com>
+---
+ fs/proc/proc_sysctl.c | 3 ++-
+ 1 file changed, 2 insertions(+), 1 deletion(-)
+
+diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
+index 55313d9..d4e37ac 100644
+--- a/fs/proc/proc_sysctl.c
++++ b/fs/proc/proc_sysctl.c
+@@ -709,7 +709,7 @@ static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
+ ctl_dir = container_of(head, struct ctl_dir, header);
+
+ if (!dir_emit_dots(file, ctx))
+- return 0;
++ goto out;
+
+ pos = 2;
+
+@@ -719,6 +719,7 @@ static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
+ break;
+ }
+ }
++out:
+ sysctl_head_finish(head);
+ return 0;
+ }
+--
+2.1.4
+
diff --git a/debian/patches/series b/debian/patches/series
index 14e5a83..f305704 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -94,6 +94,7 @@ features/all/securelevel/arm64-add-kernel-config-option-to-set-securelevel-wh.pa
# Security fixes
debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
+bugfix/all/sysctl-Drop-reference-added-by-grab_header-in-proc_s.patch
# Fix exported symbol versions
bugfix/ia64/revert-ia64-move-exports-to-definitions.patch
--
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