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 <[email protected]> Cc: Dustin Kirkland <[email protected]> Cc: [email protected] Signed-off-by: Duane Griffin <[email protected]> Acked-by: Michael Halcrow <[email protected]> Acked-by: Tyler Hicks <[email protected]> Signed-off-by: Al Viro <[email protected]>
chewitt · Dec 31, 2008 · a17d523 · a17d523
1 parent 5cc4a03
commit a17d523
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
@@ -673,10 +673,11 @@ 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;