[PATCH 3.2 52/87] cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

[Ben Hutchings]

3.2.77-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Vasily Averin <vvs@xxxxxxxxxxxxx>

commit 01b9b0b28626db4a47d7f48744d70abca9914ef1 upstream.

In some cases tmp_bug can be not filled in cifs_filldir and stay uninitialized,
therefore its printk with "%s" modifier can leak content of kernelspace memory.
If old content of this buffer does not contain '\0' access bejond end of
allocated object can crash the host.

Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
Signed-off-by: Steve French <sfrench@xxxxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 fs/cifs/readdir.c | 1 +
 1 file changed, 1 insertion(+)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -823,6 +823,7 @@ int cifs_readdir(struct file *file, void
 			}
 			/* if buggy server returns . and .. late do
 			we want to check for that here? */
+			*tmp_buf = 0;
 			rc = cifs_filldir(current_entry, file,
 					filldir, direntry, tmp_buf, max_len);
 			if (rc == -EOVERFLOW) {