[patch added to 3.12-stable] apparmor: fix refcount race when finding a child profile
From: Jiri Slaby <hidden>
Date: 2017-01-27 10:50:02
Subsystem:
apparmor security module, security subsystem, the rest · Maintainers:
John Johansen, Georgia Garcia, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
From: John Johansen <john.johansen@canonical.com> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== 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 <redacted> Signed-off-by: Jiri Slaby <redacted> --- security/apparmor/policy.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c
index ca402d028db8..780712553651 100644
--- a/security/apparmor/policy.c
+++ b/security/apparmor/policy.c@@ -766,7 +766,9 @@ struct aa_profile *aa_find_child(struct aa_profile *parent, const char *name) 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 */
--
2.11.0