[PATCH 4.4 053/137] cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

Greg Kroah-Hartman
2016-02-24T04:43:32Z

From: Vasily Averin <vvs@virtuozzo.com>

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@virtuozzo.com>
Signed-off-by: Steve French <sfrench@localhost.localdomain>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/readdir.c | 1 +
1 file changed, 1 insertion(+)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -847,6 +847,7 @@ int cifs_readdir(struct file *file, stru
* if buggy server returns . and .. late do we want to
* check for that here?
*/
+ *tmp_buf = 0;
rc = cifs_filldir(current_entry, file, ctx,
tmp_buf, max_len);
if (rc) {