From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Mon, 19 Mar 2018 11:07:45 +0000 (+0300)
Subject: staging: ncpfs: memory corruption in ncp_read_kernel()
X-Git-Tag: v3.2.102~133
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=38643d20b4d4ac378046e51b15556f0f7dc489ea;p=thirdparty%2Fkernel%2Fstable.git

staging: ncpfs: memory corruption in ncp_read_kernel()

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@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[carnil: backport to 4.9: Files renamed from drivers/staging/ncpfs/ncplib_kernel.c
 to fs/ncpfs/ncplib_kernel.c]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/fs/ncpfs/ncplib_kernel.c b/fs/ncpfs/ncplib_kernel.c
index 981a95617fc9f..76c6a8e3e8305 100644
--- a/fs/ncpfs/ncplib_kernel.c
+++ b/fs/ncpfs/ncplib_kernel.c
@@ -982,6 +982,10 @@ ncp_read_kernel(struct ncp_server *server, const char *file_id,
 		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);