ksmbd: fix slab-out-of-bounds in smb_strndup_from_utf16()

If ->NameOffset/Length is bigger than ->CreateContextsOffset/Length,
ksmbd_check_message doesn't validate request buffer it correctly.
So slab-out-of-bounds warning from calling smb_strndup_from_utf16()
in smb2_open() could happen. If ->NameLength is non-zero, Set the larger
of the two sums (Name and CreateContext size) as the offset and length of
the data area.

Reported-by: Yang Chaoming <lometsj@live.com>
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/server/smb2misc.c b/fs/smb/server/smb2misc.c
index 23bd3d1209dfa53feb4f094989b2f9c5f3a67603..03dded29a9804205f7f96802d99beb28a1c8eaf9 100644 (file)
--- a/fs/smb/server/smb2misc.c
+++ b/fs/smb/server/smb2misc.c
@@ -106,16 +106,25 @@ static int smb2_get_data_area_len(unsigned int *off, unsigned int *len,
                break;
        case SMB2_CREATE:
        {
+               unsigned short int name_off =
+                       le16_to_cpu(((struct smb2_create_req *)hdr)->NameOffset);
+               unsigned short int name_len =
+                       le16_to_cpu(((struct smb2_create_req *)hdr)->NameLength);
+
                if (((struct smb2_create_req *)hdr)->CreateContextsLength) {
                        *off = le32_to_cpu(((struct smb2_create_req *)
                                hdr)->CreateContextsOffset);
                        *len = le32_to_cpu(((struct smb2_create_req *)
                                hdr)->CreateContextsLength);
-                       break;
+                       if (!name_len)
+                               break;
+
+                       if (name_off + name_len < (u64)*off + *len)
+                               break;
                }
 
-               *off = le16_to_cpu(((struct smb2_create_req *)hdr)->NameOffset);
-               *len = le16_to_cpu(((struct smb2_create_req *)hdr)->NameLength);
+               *off = name_off;
+               *len = name_len;
                break;
        }
        case SMB2_QUERY_INFO: