Patch "apparmor: fix refcount race when finding a child profile" has been added to the 4.7-stable tree

Patch "apparmor: fix refcount race when finding a child profile" has been added to the 4.7-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    apparmor: fix refcount race when finding a child profile

to the 4.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     apparmor-fix-refcount-race-when-finding-a-child-profile.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From de7c4cc947f9f56f61520ee7edaf380434a98c8d Mon Sep 17 00:00:00 2001
From: John Johansen <john.johansen@canonical.com>
Date: Wed, 16 Dec 2015 18:09:10 -0800
Subject: apparmor: fix refcount race when finding a child profile

From: John Johansen <john.johansen@canonical.com>

commit de7c4cc947f9f56f61520ee7edaf380434a98c8d upstream.

When finding a child profile via an rcu critical section, the profile
may be put and scheduled for deletion after the child is found but
before its refcount is incremented.

Protect against this by repeating the lookup if the profiles refcount
is 0 and is one its way to deletion.

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 security/apparmor/policy.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/security/apparmor/policy.c
+++ b/security/apparmor/policy.c
@@ -766,7 +766,9 @@ struct aa_profile *aa_find_child(struct
 	struct aa_profile *profile;
 
 	rcu_read_lock();
-	profile = aa_get_profile(__find_child(&parent->base.profiles, name));
+	do {
+		profile = __find_child(&parent->base.profiles, name);
+	} while (profile && !aa_get_profile_not0(profile));
 	rcu_read_unlock();
 
 	/* refcount released by caller */


Patches currently in stable-queue which might be from john.johansen@canonical.com are

queue-4.7/apparmor-fix-refcount-race-when-finding-a-child-profile.patch