[PATCH] apparmor: Fix two bugs of aa_setup_dfa_engine's fail handling

[GONG Ruiqi]

First, aa_dfa_unpack returns ERR_PTR not NULL when it fails, but
aa_put_dfa only checks NULL for its input, which would cause invalid
memory access in aa_put_dfa. Set nulldfa to NULL explicitly to fix that.

Second, aa_put_pdb calls aa_pdb_free_kref -> aa_free_pdb -> aa_put_dfa,
i.e.  it will free nullpdb->dfa. But there's another aa_put_dfa(nulldfa)
after aa_put_pdb(nullpdb), which would cause double free. Remove that
redundant aa_put_dfa to fix that.

Fixes: 98b824ff8984 ("apparmor: refcount the pdb")
Signed-off-by: GONG Ruiqi <gongruiqi1@xxxxxxxxxx>
---
 security/apparmor/lsm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index c1d42fc72fdb..be82ec1b9fd9 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -2465,6 +2465,7 @@ static int __init aa_setup_dfa_engine(void)
 			    TO_ACCEPT2_FLAG(YYTD_DATA32));
 	if (IS_ERR(nulldfa)) {
 		error = PTR_ERR(nulldfa);
+		nulldfa = NULL;
 		goto fail;
 	}
 	nullpdb->dfa = aa_get_dfa(nulldfa);
@@ -2486,7 +2487,6 @@ static int __init aa_setup_dfa_engine(void)
 
 fail:
 	aa_put_pdb(nullpdb);
-	aa_put_dfa(nulldfa);
 	nullpdb = NULL;
 	nulldfa = NULL;
 	stacksplitdfa = NULL;
-- 
2.43.0