[PATCH] CIFS: fix cifs_user_read oops when null SMB response on forcedirectio mount

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@austin.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 6 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index d17c97d07c80..675bd2568297 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1442,13 +1442,15 @@ ssize_t cifs_user_read(struct file *file, char __user *read_data,
                                          &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)