[PATCH v2] apparmor: Fix use-after-free in aa_audit_rule_init

[Navid Emamdoost]

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: 52e8c38001d8 ("apparmor: Fix memory leak of rule on error exit path")
Signed-off-by: Navid Emamdoost <navid.emamdo...@gmail.com>
---
Changes in v2:
        -- Fix typo in description
        -- move err definition inside the if statement.

 security/apparmor/audit.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/apparmor/audit.c b/security/apparmor/audit.c
index 5a98661a8b46..334065302fb6 100644
--- 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 = rule->label;
                aa_audit_rule_free(rule);
-               return PTR_ERR(rule->label);
+               return PTR_ERR(err);
        }
 
        *vrule = rule;
-- 
2.17.1