cifs: check offset in decode_ntlmssp_challenge()

We should check that we're not copying memory from beyond the end of the
blob.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index d85efad5765f..eb767412177d 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -395,6 +395,10 @@ static int decode_ntlmssp_challenge(char *bcc_ptr, int blob_len,
         ses->ntlmssp->server_flags = le32_to_cpu(pblob->NegotiateFlags);
         tioffset = le32_to_cpu(pblob->TargetInfoArray.BufferOffset);
         tilen = le16_to_cpu(pblob->TargetInfoArray.Length);
+        if (tioffset > blob_len || tioffset + tilen > blob_len) {
+                cERROR(1, "tioffset + tilen too high %u + %u", tioffset, tilen);
+                return -EINVAL;
+        }
         if (tilen) {
                 ses->auth_key.response = kmalloc(tilen, GFP_KERNEL);
                 if (!ses->auth_key.response) {