[PATCH 2/2] net/9p: Return error on read with NULL buffer

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

From: Sanchit Garg <sancgarg@linux.vnet.ibm.com>

This patch ensures that a read(fd, NULL, 0 ) returns  EFAULT on a 9p file.

Signed-off-by: Sanchit Garg <sancgarg@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 net/9p/client.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index e141e46..d5344d8 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1313,6 +1313,11 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,
 	rsize = fid->iounit;
 	if (!rsize || rsize > clnt->msize-P9_IOHDRSZ)
 		rsize = clnt->msize - P9_IOHDRSZ;
+	/*
+	 * A read with NULL user buffer cause EFAULT error
+	 */
+	if (!data && !udata)
+		return -EFAULT;
 
 	if (count < rsize)
 		rsize = count;
@@ -1333,16 +1338,13 @@ p9_client_read(struct p9_fid *fid, char *data, char __user *udata, u64 offset,
 
 	if (data) {
 		memmove(data, dataptr, count);
-	}
-
-	if (udata) {
+	} else {
 		err = copy_to_user(udata, dataptr, count);
 		if (err) {
 			err = -EFAULT;
 			goto free_and_error;
 		}
 	}
-
 	p9_free_req(clnt, req);
 	return count;
 
-- 
1.7.1