3.18-stable patches

added patches:
	mm-oom-fix-use-after-free-in-oom_kill_process.patch

diff --git a/queue-3.18/mm-oom-fix-use-after-free-in-oom_kill_process.patch b/queue-3.18/mm-oom-fix-use-after-free-in-oom_kill_process.patch
new file mode 100644 (file)
index 0000000..4e3dfb5
--- /dev/null
+++ b/queue-3.18/mm-oom-fix-use-after-free-in-oom_kill_process.patch
@@ -0,0 +1,70 @@
+From cefc7ef3c87d02fc9307835868ff721ea12cc597 Mon Sep 17 00:00:00 2001
+From: Shakeel Butt <shakeelb@google.com>
+Date: Fri, 1 Feb 2019 14:20:54 -0800
+Subject: mm, oom: fix use-after-free in oom_kill_process
+
+From: Shakeel Butt <shakeelb@google.com>
+
+commit cefc7ef3c87d02fc9307835868ff721ea12cc597 upstream.
+
+Syzbot instance running on upstream kernel found a use-after-free bug in
+oom_kill_process.  On further inspection it seems like the process
+selected to be oom-killed has exited even before reaching
+read_lock(&tasklist_lock) in oom_kill_process().  More specifically the
+tsk->usage is 1 which is due to get_task_struct() in oom_evaluate_task()
+and the put_task_struct within for_each_thread() frees the tsk and
+for_each_thread() tries to access the tsk.  The easiest fix is to do
+get/put across the for_each_thread() on the selected task.
+
+Now the next question is should we continue with the oom-kill as the
+previously selected task has exited? However before adding more
+complexity and heuristics, let's answer why we even look at the children
+of oom-kill selected task? The select_bad_process() has already selected
+the worst process in the system/memcg.  Due to race, the selected
+process might not be the worst at the kill time but does that matter?
+The userspace can use the oom_score_adj interface to prefer children to
+be killed before the parent.  I looked at the history but it seems like
+this is there before git history.
+
+Link: http://lkml.kernel.org/r/20190121215850.221745-1-shakeelb@google.com
+Reported-by: syzbot+7fbbfa368521945f0e3d@syzkaller.appspotmail.com
+Fixes: 6b0c81b3be11 ("mm, oom: reduce dependency on tasklist_lock")
+Signed-off-by: Shakeel Butt <shakeelb@google.com>
+Reviewed-by: Roman Gushchin <guro@fb.com>
+Acked-by: Michal Hocko <mhocko@suse.com>
+Cc: David Rientjes <rientjes@google.com>
+Cc: Johannes Weiner <hannes@cmpxchg.org>
+Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
+Cc: <stable@vger.kernel.org>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ mm/oom_kill.c |    8 ++++++++
+ 1 file changed, 8 insertions(+)
+
+--- a/mm/oom_kill.c
++++ b/mm/oom_kill.c
+@@ -464,6 +464,13 @@ void oom_kill_process(struct task_struct
+        * still freeing memory.
+        */
+       read_lock(&tasklist_lock);
++
++      /*
++       * The task 'p' might have already exited before reaching here. The
++       * put_task_struct() will free task_struct 'p' while the loop still try
++       * to access the field of 'p', so, get an extra reference.
++       */
++      get_task_struct(p);
+       for_each_thread(p, t) {
+               list_for_each_entry(child, &t->children, sibling) {
+                       unsigned int child_points;
+@@ -483,6 +490,7 @@ void oom_kill_process(struct task_struct
+                       }
+               }
+       }
++      put_task_struct(p);
+       read_unlock(&tasklist_lock);
+ 
+       p = find_lock_task_mm(victim);

diff --git a/queue-3.18/series b/queue-3.18/series
index d17cf45b56a03d6c22410128c31b7097eb2eddb9..2a215435cedce86bee99ddb29dd58074ffbd61a6 100644 (file)
--- a/queue-3.18/series
+++ b/queue-3.18/series
@@ -27,3 +27,4 @@ arm64-hyp-stub-forbid-kprobing-of-the-hyp-stub.patch
 gfs2-revert-fix-loop-in-gfs2_rbm_find.patch
 platform-x86-asus-nb-wmi-map-0x35-to-key_screenlock.patch
 platform-x86-asus-nb-wmi-drop-mapping-of-0x33-and-0x.patch
+mm-oom-fix-use-after-free-in-oom_kill_process.patch