apparmor: Fix use-after-free in aa_audit_rule_init

In the implementation of aa_audit_rule_init(), when aa_label_parse()
fails the allocated memory for rule is released using
aa_audit_rule_free(). But after this release, the return statement
tries to access the label field of the rule which results in
use-after-free. Before releasing the rule, copy errNo and return it
after release.

Fixes: e7de3b57db1b ("apparmor: Fix memory leak of rule on error exit path")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

diff --git a/security/apparmor/audit.c b/security/apparmor/audit.c
index 5a98661a8b46ea2daf47a3386d2fe181622a977b..5977325038157dc5a12a2d4ed663d7e09f8dbace 100644 (file)
--- a/security/apparmor/audit.c
+++ b/security/apparmor/audit.c
@@ -197,8 +197,9 @@ int aa_audit_rule_init(u32 field, u32 op, char *rulestr, void **vrule)
        rule->label = aa_label_parse(&root_ns->unconfined->label, rulestr,
                                     GFP_KERNEL, true, false);
        if (IS_ERR(rule->label)) {
+               int err = PTR_ERR(rule->label);
                aa_audit_rule_free(rule);
-               return PTR_ERR(rule->label);
+               return err;
        }
 
        *vrule = rule;