[PATCH 4.15 074/105] staging: ncpfs: memory corruption in ncp_read_kernel()

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

commit 4c41aa24baa4ed338241d05494f2c595c885af8f upstream.

If the server is malicious then *bytes_read could be larger than the
size of the "target" buffer.  It would lead to memory corruption when we
do the memcpy().

Reported-by: Dr Silvio Cesare of InfoSect <Silvio Cesare <silvio.cesare@xxxxxxxxx>
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/ncpfs/ncplib_kernel.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/fs/ncpfs/ncplib_kernel.c
+++ b/fs/ncpfs/ncplib_kernel.c
@@ -981,6 +981,10 @@ ncp_read_kernel(struct ncp_server *serve
 		goto out;
 	}
 	*bytes_read = ncp_reply_be16(server, 0);
+	if (*bytes_read > to_read) {
+		result = -EINVAL;
+		goto out;
+	}
 	source = ncp_reply_data(server, 2 + (offset & 1));
 
 	memcpy(target, source, *bytes_read);