FAILED: patch "[PATCH] apparmor: fix out-of-bounds write when null terminating a" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 9f1e40193eef7f047e6b77cfb4b4cafdecd7a123
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090321-antitrust-overlord-343b@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9f1e40193eef7f047e6b77cfb4b4cafdecd7a123 Mon Sep 17 00:00:00 2001
From: Hyunwoo Kim <[email protected]>
Date: Mon, 10 Aug 2026 18:51:33 +0900
Subject: [PATCH] apparmor: fix out-of-bounds write when null terminating a
label vec

aa_vec_unique() null terminates at vec[n - dups] when VEC_FLAG_TERMINATE is passed. If the components are all distinct no duplicates are dropped, dups is 0 and the terminator goes to vec[n], so the caller has to provide room for n + 1 entries.

aa_label_strn_parse() sets up its vector with vec_setup(profile, vec, len, gfp) and then calls aa_vec_unique(vec, len, VEC_FLAG_TERMINATE), but vec_setup() does not reserve the terminator entry. Up to LOCAL_VEC_ENTRIES it uses the local array of LOCAL_VEC_ENTRIES pointers, above that it allocates exactly len pointers. The terminator therefore lands one entry past the end of the local array when len is LOCAL_VEC_ENTRIES, and one entry past the end of the allocation when len is larger.

len comes from the number of "//&" separated components in the label name and label_count_strn_entries() does not bound it. An unprivileged task reaches the parse by writing to /proc/self/attr/apparmor/current or through lsm_set_self_attr(2), both of which go through do_setattr(), and the name is parsed before the change_profile permission is checked.
The query_label() path behind the securityfs .access file, which is mode 0666, performs no permission check at all. Every component has to resolve to a loaded profile, so a system with policy loaded is required.

The other two VEC_FLAG_TERMINATE users work on a label vec that aa_label_alloc() has already sized with "+ 1 for null terminator entry on vec". Reserve the same entry in vec_setup() and DEFINE_VEC(). Passing len + 1 from the caller instead would move len == LOCAL_VEC_ENTRIES out of the local array and into kzalloc().

index b5a722a47fd2..37cb135de323 100644
@@ -23,7 +23,7 @@ struct aa_ruleset;
 
 #define LOCAL_VEC_ENTRIES 8
 #define DEFINE_VEC(T, V)						\
-	struct aa_ ## T *(_ ## V ## _localtmp)[LOCAL_VEC_ENTRIES];	\
+	struct aa_ ## T *(_ ## V ## _localtmp)[LOCAL_VEC_ENTRIES + 1];	\
 	struct aa_ ## T **(V)
 
 #define vec_setup(T, V, N, GFP)						\

@@ -31,10 +31,10 @@ struct aa_ruleset;
 	if ((N) <= LOCAL_VEC_ENTRIES) {					\
 		typeof(N) i;						\
 		(V) = (_ ## V ## _localtmp);				\
-		for (i = 0; i < (N); i++)				\
+		for (i = 0; i <= (N); i++)				\
 			(V)[i] = NULL;					\
 	} else								\
-		(V) = kzalloc(sizeof(struct aa_ ## T *) * (N), (GFP));	\
+		(V) = kzalloc_objs(struct aa_ ## T *, (N) + 1, (GFP));	\
 	(V) ? 0 : -ENOMEM;						\
 })
 

From: Hyunwoo Kim <[email protected]>

[ Upstream commit 9f1e40193eef7f047e6b77cfb4b4cafdecd7a123 ]

aa_vec_unique() null terminates at vec[n - dups] when VEC_FLAG_TERMINATE is passed. If the components are all distinct no duplicates are dropped, dups is 0 and the terminator goes to vec[n], so the caller has to provide room for n + 1 entries.

aa_label_strn_parse() sets up its vector with vec_setup(profile, vec, len, gfp) and then calls aa_vec_unique(vec, len, VEC_FLAG_TERMINATE), but vec_setup() does not reserve the terminator entry. Up to LOCAL_VEC_ENTRIES it uses the local array of LOCAL_VEC_ENTRIES pointers, above that it allocates exactly len pointers. The terminator therefore lands one entry past the end of the local array when len is LOCAL_VEC_ENTRIES, and one entry past the end of the allocation when len is larger.

len comes from the number of "//&" separated components in the label name and label_count_strn_entries() does not bound it. An unprivileged task reaches the parse by writing to /proc/self/attr/apparmor/current or through lsm_set_self_attr(2), both of which go through do_setattr(), and the name is parsed before the change_profile permission is checked.
The query_label() path behind the securityfs .access file, which is mode 0666, performs no permission check at all. Every component has to resolve to a loaded profile, so a system with policy loaded is required.

The other two VEC_FLAG_TERMINATE users work on a label vec that aa_label_alloc() has already sized with "+ 1 for null terminator entry on vec". Reserve the same entry in vec_setup() and DEFINE_VEC(). Passing len + 1 from the caller instead would move len == LOCAL_VEC_ENTRIES out of the local array and into kzalloc().

---
 security/apparmor/include/label.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 9887bfbab0f3d..43565faae2ba5 100644
@@ -22,7 +22,7 @@ struct aa_ns;
 
 #define LOCAL_VEC_ENTRIES 8
 #define DEFINE_VEC(T, V)						\
-	struct aa_ ## T *(_ ## V ## _localtmp)[LOCAL_VEC_ENTRIES];	\
+	struct aa_ ## T *(_ ## V ## _localtmp)[LOCAL_VEC_ENTRIES + 1];	\
 	struct aa_ ## T **(V)
 
 #define vec_setup(T, V, N, GFP)						\

@@ -30,10 +30,10 @@ struct aa_ns;
 	if ((N) <= LOCAL_VEC_ENTRIES) {					\
 		typeof(N) i;						\
 		(V) = (_ ## V ## _localtmp);				\
-		for (i = 0; i < (N); i++)				\
+		for (i = 0; i <= (N); i++)				\
 			(V)[i] = NULL;					\
 	} else								\
-		(V) = kzalloc(sizeof(struct aa_ ## T *) * (N), (GFP));	\
+		(V) = kcalloc((N) + 1, sizeof(struct aa_ ## T *), (GFP)); \
 	(V) ? 0 : -ENOMEM;						\
 })
 

2.53.0