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

If ->NameOffset of smb2_create_req is smaller than Buffer offset of
smb2_create_req, slab-out-of-bounds read can happen from smb2_open.
This patch set the minimum value of the name offset to the buffer offset
to validate name length of smb2_create_req().

Cc: stable@vger.kernel.org
Reported-by: Xuanzhe Yu <yuxuanzhe@outlook.com>
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 03dded29a9804205f7f96802d99beb28a1c8eaf9..7c872ffb4b0a9821bc6ed4c5d5fe394a74d15a31 100644 (file)
--- a/fs/smb/server/smb2misc.c
+++ b/fs/smb/server/smb2misc.c
@@ -107,7 +107,10 @@ static int smb2_get_data_area_len(unsigned int *off, unsigned int *len,
        case SMB2_CREATE:
        {
                unsigned short int name_off =
-                       le16_to_cpu(((struct smb2_create_req *)hdr)->NameOffset);
+                       max_t(unsigned short int,
+                             le16_to_cpu(((struct smb2_create_req *)hdr)->NameOffset),
+                             offsetof(struct smb2_create_req, Buffer));
+
                unsigned short int name_len =
                        le16_to_cpu(((struct smb2_create_req *)hdr)->NameLength);