From: Eric Sandeen <sandeen@redhat.com>
Date: Wed, 4 Feb 2009 10:02:14 -0600
Subject: [fs] ecryptfs: readlink flaw
Message-id: 4989BC06.9060709@redhat.com
O-Subject: [RHEL5 PATCH] - CVE-2009-0269 kernel: ecryptfs readlink flaw
Bugzilla: 481607
RH-Acked-by: Jeff Layton <jlayton@redhat.com>
RH-Acked-by: Peter Staubach <staubach@redhat.com>
RH-Acked-by: Jarod Wilson <jarod@redhat.com>
RH-Acked-by: Jon Masters <jcm@redhat.com>
CVE: CVE-2009-0269

This is for:

Bug 481606 - CVE-2009-0269 kernel: ecryptfs readlink flaw [rhel-5.3.z]
Bug 481607 - CVE-2009-0269 kernel: ecryptfs readlink flaw [rhel-5.4]

Pretty straightforward error and fix, see below:

From: Duane Griffin <duaneg@dghda.com>
Date: Fri, 19 Dec 2008 20:47:10 +0000 (+0000)
Subject: eCryptfs: check readlink result was not an error before using it
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Fstable%2Flinux-2.6.27.y.git;a=commitdiff_plain;h=a17d5232de7b53d34229de79ec22f4bb04adb7e4

eCryptfs: check readlink result was not an error before using it

The result from readlink is being used to index into the link name
buffer without checking whether it is a valid length. If readlink
returns an error this will fault or cause memory corruption.

Cc: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Cc: Dustin Kirkland <kirkland@canonical.com>
Cc: ecryptfs-devel@lists.launchpad.net
Signed-off-by: Duane Griffin <duaneg@dghda.com>
Acked-by: Michael Halcrow <mhalcrow@us.ibm.com>
Acked-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index de9becd..cf600a1 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -675,10 +675,11 @@ static void *ecryptfs_follow_link(struct dentry *dentry, struct nameidata *nd)
 	ecryptfs_printk(KERN_DEBUG, "Calling readlink w/ "
 			"dentry->d_name.name = [%s]\n", dentry->d_name.name);
 	rc = dentry->d_inode->i_op->readlink(dentry, (char __user *)buf, len);
-	buf[rc] = '\0';
 	set_fs(old_fs);
 	if (rc < 0)
 		goto out_free;
+	else
+		buf[rc] = '\0';
 	rc = 0;
 	nd_set_link(nd, buf);
 	goto out;