apparmor: Fix & Optimize table creation from possibly unaligned memory

[ Upstream commit 6fc367b ]

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: e6e8bf4 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: hdeller

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)

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