From 8404d7a674c49278607d19726e0acc0cae299357 Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@google.com>
Date: Tue, 28 May 2019 17:32:26 +0200
Subject: [PATCH] apparmor: enforce nullbyte at end of tag string
Git-commit: 8404d7a674c49278607d19726e0acc0cae299357
Patch-mainline: v5.2-rc6
References: bsc#1051510

A packed AppArmor policy contains null-terminated tag strings that are read
by unpack_nameX(). However, unpack_nameX() uses string functions on them
without ensuring that they are actually null-terminated, potentially
leading to out-of-bounds accesses.

Make sure that the tag string is null-terminated before passing it to
strcmp().

Cc: stable@vger.kernel.org
Fixes: 736ec752d95e ("AppArmor: policy routines for loading and unpacking policy")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 security/apparmor/policy_unpack.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c
index 01957ce9252b..005a705346f0 100644
--- a/security/apparmor/policy_unpack.c
+++ b/security/apparmor/policy_unpack.c
@@ -272,7 +272,7 @@ static bool unpack_nameX(struct aa_ext *e, enum aa_code code, const char *name)
 		char *tag = NULL;
 		size_t size = unpack_u16_chunk(e, &tag);
 		/* if a name is specified it must match. otherwise skip tag */
-		if (name && (!size || strcmp(name, tag)))
+		if (name && (!size || tag[size-1] != '\0' || strcmp(name, tag)))
 			goto fail;
 	} else if (name) {
 		/* if a name is specified and there is no name tag fail */
-- 
2.16.4