ovl: copy_up_xattr(): use strnlen

commit 8b326c61de08f5ca4bc454a168f19e7e43c4cc2a upstream.

Be defensive about what underlying fs provides us in the returned xattr
list buffer.  strlen() may overrun the buffer, so use strnlen() and WARN if
the contents are not properly null terminated.

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

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 9e52609cd683d9ca5706aff277a158b7b8e03d18..ea0dd9ee138d2209cdd2017ff52070faf5116754 100644 (file)
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -25,6 +25,7 @@ int ovl_copy_xattr(struct dentry *old, struct dentry *new)
        ssize_t list_size, size, value_size = 0;
        char *buf, *name, *value = NULL;
        int uninitialized_var(error);
+       size_t slen;
 
        if (!old->d_inode->i_op->getxattr ||
            !new->d_inode->i_op->getxattr)
@@ -47,7 +48,16 @@ int ovl_copy_xattr(struct dentry *old, struct dentry *new)
                goto out;
        }
 
-       for (name = buf; name < (buf + list_size); name += strlen(name) + 1) {
+       for (name = buf; list_size; name += slen) {
+               slen = strnlen(name, list_size) + 1;
+
+               /* underlying fs providing us with an broken xattr list? */
+               if (WARN_ON(slen > list_size)) {
+                       error = -EIO;
+                       break;
+               }
+               list_size -= slen;
+
                if (ovl_is_private_xattr(name))
                        continue;
 retry: