[PATCH 6.6.y 2/2] apparmor: Fix & Optimize table creation from possibly unaligned memory

[Artem Dinaburg <artem@trailofbits.com>]

From: Helge Deller <deller@kernel.org>

[ Upstream commit 6fc367bfd4c8886e6b1742aabbd1c0bdc310db3a ]

Source blob may come from userspace and might be unaligned.
Try to optize the copying process by avoiding unaligned memory accesses.

- Added Fixes tag
- Added "Fix &" to description as this doesn't just optimize but fixes
        a potential unaligned memory access
Fixes: e6e8bf418850d ("apparmor: fix restricted endian type warnings for dfa unpack")
Signed-off-by: Helge Deller <deller@gmx.de>
[jj: remove duplicate word "convert" in comment trigger checkpatch warning]
Signed-off-by: John Johansen <john.johansen@canonical.com>
Assisted-by: LLM
Signed-off-by: Artem Dinaburg <artem@trailofbits.com>
---
This is patch 2 of 2 in the ordered 6.6.y backport series.
This change addresses CVE-2026-45893. The userspace policy blob may be
unaligned, so typed __be16 and __be32 array loads can fault.
The source diff is identical to upstream. 

The fix is already present in 6.12.y, 6.18.y, and 7.2.y, but not in 6.6.y.
This fix also affects 6.1.y, which will need a separate backport; this
submission contains only the 6.6.y patch.

 security/apparmor/include/match.h | 12 +++++++-----
 security/apparmor/match.c         |  7 +++----
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/security/apparmor/include/match.h b/security/apparmor/include/match.h
index a86f74b59360..14c0401f97c1 100644
--- a/security/apparmor/include/match.h
+++ b/security/apparmor/include/match.h
@@ -102,16 +102,18 @@ struct aa_dfa {
 	struct table_header *tables[YYTD_ID_TSIZE];
 };
 
-#define byte_to_byte(X) (X)
-
 #define UNPACK_ARRAY(TABLE, BLOB, LEN, TTYPE, BTYPE, NTOHX)	\
 	do { \
 		typeof(LEN) __i; \
 		TTYPE *__t = (TTYPE *) TABLE; \
 		BTYPE *__b = (BTYPE *) BLOB; \
-		for (__i = 0; __i < LEN; __i++) { \
-			__t[__i] = NTOHX(__b[__i]); \
-		} \
+		BUILD_BUG_ON(sizeof(TTYPE) != sizeof(BTYPE)); \
+		if (IS_ENABLED(CONFIG_CPU_BIG_ENDIAN)) \
+			memcpy(__t, __b, (LEN) * sizeof(BTYPE)); \
+		else /* copy & convert from big-endian */ \
+			for (__i = 0; __i < LEN; __i++) { \
+				__t[__i] = NTOHX(&__b[__i]); \
+			} \
 	} while (0)
 
 static inline size_t table_size(size_t len, size_t el_size)
diff --git a/security/apparmor/match.c b/security/apparmor/match.c
index 19b44e705b26..0a3307cd4107 100644
--- a/security/apparmor/match.c
+++ b/security/apparmor/match.c
@@ -67,14 +67,13 @@ static struct table_header *unpack_table(char *blob, size_t bsize)
 		table->td_flags = th.td_flags;
 		table->td_lolen = th.td_lolen;
 		if (th.td_flags == YYTD_DATA8)
-			UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
-				     u8, u8, byte_to_byte);
+			memcpy(table->td_data, blob, th.td_lolen);
 		else if (th.td_flags == YYTD_DATA16)
 			UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
-				     u16, __be16, be16_to_cpu);
+				     u16, __be16, get_unaligned_be16);
 		else if (th.td_flags == YYTD_DATA32)
 			UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
-				     u32, __be32, be32_to_cpu);
+				     u32, __be32, get_unaligned_be32);
 		else
 			goto fail;
 		/* if table was vmalloced make sure the page tables are synced
-- 
2.39.5