From: Miklos Szeredi <mszeredi@redhat.com>
Date: Thu, 1 Sep 2016 09:12:00 +0000 (+0200)
Subject: ovl: listxattr: use strnlen()
X-Git-Tag: v4.7.4~27
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=774b544fb06318ee9e345d180102bcfc47ebe587;p=thirdparty%2Fkernel%2Fstable.git

ovl: listxattr: use strnlen()

commit 7cb35119d067191ce9ebc380a599db0b03cbd9d9 upstream.

Be defensive about what underlying fs provides us in the returned xattr
list buffer.  If it's not properly null terminated, bail out with a warning
insead of BUG.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 1ed710044ec01..ac98a71e753a5 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -279,24 +279,27 @@ ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
 {
 	struct dentry *realdentry = ovl_dentry_real(dentry);
 	ssize_t res;
-	int off;
+	size_t len;
+	char *s;
 
 	res = vfs_listxattr(realdentry, list, size);
 	if (res <= 0 || size == 0)
 		return res;
 
 	/* filter out private xattrs */
-	for (off = 0; off < res;) {
-		char *s = list + off;
-		size_t slen = strlen(s) + 1;
+	for (s = list, len = res; len;) {
+		size_t slen = strnlen(s, len) + 1;
 
-		BUG_ON(off + slen > res);
+		/* underlying fs providing us with an broken xattr list? */
+		if (WARN_ON(slen > len))
+			return -EIO;
 
+		len -= slen;
 		if (ovl_is_private_xattr(s)) {
 			res -= slen;
-			memmove(s, s + slen, res - off);
+			memmove(s, s + slen, len);
 		} else {
-			off += slen;
+			s += slen;
 		}
 	}