[PATCH] [CIFS] fix cifs_user_read oops when null SMB response onforcedirectio mount

[Steve French]

This patch fixes an oops reported by Adrian Bunk in cifs_user_read when a null 
read response is returned on a forcedirectio mount.  

Signed-off-by: Dave Kleikamp <shaggy@xxxxxxxxxxxxxx>
Signed-off-by: Steve French <sfrench@xxxxxxxxxx>

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index d17c97d..675bd25 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1442,13 +1442,15 @@ ssize_t cifs_user_read(struct file *file
					 &bytes_read, &smb_read_data,
					 &buf_type);
			pSMBr = (struct smb_com_read_rsp *)smb_read_data;
-			if (copy_to_user(current_offset, 
-					 smb_read_data + 4 /* RFC1001 hdr */
-					 + le16_to_cpu(pSMBr->DataOffset), 
-					 bytes_read)) {
-				rc = -EFAULT;
-			}
			if (smb_read_data) {
+				if (copy_to_user(current_offset,
+						smb_read_data +
+						4 /* RFC1001 length field */ +
+						le16_to_cpu(pSMBr->DataOffset),
+						bytes_read)) {
+					rc = -EFAULT;
+				}
+
				if(buf_type == CIFS_SMALL_BUFFER)
					cifs_small_buf_release(smb_read_data);
				else if(buf_type == CIFS_LARGE_BUFFER)


diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index d17c97d..675bd25 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1442,13 +1442,15 @@ ssize_t cifs_user_read(struct file *file
 					 &bytes_read, &smb_read_data,
 					 &buf_type);
 			pSMBr = (struct smb_com_read_rsp *)smb_read_data;
-			if (copy_to_user(current_offset, 
-					 smb_read_data + 4 /* RFC1001 hdr */
-					 + le16_to_cpu(pSMBr->DataOffset), 
-					 bytes_read)) {
-				rc = -EFAULT;
-			}
 			if (smb_read_data) {
+				if (copy_to_user(current_offset,
+						smb_read_data +
+						4 /* RFC1001 length field */ +
+						le16_to_cpu(pSMBr->DataOffset),
+						bytes_read)) {
+					rc = -EFAULT;
+				}
+
 				if(buf_type == CIFS_SMALL_BUFFER)
 					cifs_small_buf_release(smb_read_data);
 				else if(buf_type == CIFS_LARGE_BUFFER)