linux-kernel - [PATCH 3.2 52/87] cifs_dbg() outputs an uninitialized buffer in cifs

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Date:	Mon, 08 Feb 2016 23:53:51 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Vasily Averin" <vvs@...tuozzo.com>,
	"Steve French" <sfrench@...alhost.localdomain>
Subject: [PATCH 3.2 52/87] cifs_dbg() outputs an uninitialized buffer in
 cifs_readdir()

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

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

From: Vasily Averin <vvs@...tuozzo.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@...tuozzo.com>
Signed-off-by: Steve French <sfrench@...alhost.localdomain>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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) {