apparmor: fix overlapping attachment computation

stable inclusion
from stable-v5.10.138
commit 2672f3eb7a7f8bc076a146c6f062233f56b1d3c1
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I60QFD

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2672f3eb7a7f8bc076a146c6f062233f56b1d3c1

--------------------------------

commit 2504db20 upstream.

When finding the profile via patterned attachments, the longest left
match is being set to the static compile time value and not using the
runtime computed value.

Fix this by setting the candidate value to the greater of the
precomputed value or runtime computed value.

Fixes: 21f60661 ("apparmor: improve overlapping domain attachment resolution")
Signed-off-by: NJohn Johansen <john.johansen@canonical.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>

security/apparmor/domain.c

@@ -465,7 +465,7 @@ static struct aa_label *find_attach(const struct linux_binprm *bprm,
 				 * xattrs, or a longer match
 				 */
 				candidate = profile;
-				candidate_len = profile->xmatch_len;
+				candidate_len = max(count, profile->xmatch_len);
 				candidate_xattrs = ret;
 				conflict = false;
 			}

security/apparmor/include/policy.h

@@ -135,7 +135,7 @@ struct aa_profile {
 
 	const char *attach;
 	struct aa_dfa *xmatch;
-	int xmatch_len;
+	unsigned int xmatch_len;
 	enum audit_mode audit;
 	long mode;
 	u32 path_flags;