cifs: fix SID binary to string conversion

The authority fields are supposed to be represented by a single 48-bit
value. It's also supposed to represent the value as hex if it's equal to
or greater than 2^32. This is documented in MS-DTYP, section 2.4.2.1.

Also, fix up the max string length to account for this fix.

Acked-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/fs/cifs/cifsacl.h b/fs/cifs/cifsacl.h
index a445405f80d0..4f3884835267 100644
--- a/fs/cifs/cifsacl.h
+++ b/fs/cifs/cifsacl.h
@@ -55,12 +55,14 @@
  * u8:  max 3 bytes in decimal
  * u32: max 10 bytes in decimal
  *
- * "S-" + 3 bytes for version field + 4 bytes for each authority field (3 bytes
- * per number + 1 for '-') + NULL terminator.
+ * "S-" + 3 bytes for version field + 15 for authority field + NULL terminator
+ *
+ * For authority field, max is when all 6 values are non-zero and it must be
+ * represented in hex. So "-0x" + 12 hex digits.
  *
  * Add 11 bytes for each subauthority field (10 bytes each + 1 for '-')
  */
-#define SID_STRING_BASE_SIZE (2 + 3 + (4 * NUM_AUTHS) + 1)
+#define SID_STRING_BASE_SIZE (2 + 3 + 15 + 1)
 #define SID_STRING_SUBAUTH_SIZE (11) /* size of a single subauth string */
 
 struct cifs_ntsd {