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apparmor: fix refcount race when finding a child profile 

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>
This commit is contained in:
John Johansen 2015-12-16 18:09:10 -08:00
parent 0b938a2e2c
commit de7c4cc947
1 changed files with 3 additions and 1 deletions
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4
security/apparmor/policy.c
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@ -766,7 +766,9 @@ struct aa_profile *aa_find_child(struct aa_profile *parent, const char *name)
struct aa_profile *profile; struct aa_profile *profile;
rcu_read_lock(); 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(); rcu_read_unlock();
/* refcount released by caller */ /* refcount released by caller */