cifs_dbg() outputs an uninitialized buffer in cifs_readdir()

[ Upstream commit 01b9b0b28626db4a47d7f48744d70abca9914ef1 ]

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>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index b1eede3..3634c7a 100644 (file)
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -847,6 +847,7 @@ int cifs_readdir(struct file *file, struct dir_context *ctx)
                 * 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) {