From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753666Ab2CWUtD (ORCPT ); Fri, 23 Mar 2012 16:49:03 -0400 Received: from mail-pz0-f52.google.com ([209.85.210.52]:62380 "EHLO mail-pz0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751838Ab2CWUtA (ORCPT ); Fri, 23 Mar 2012 16:49:00 -0400 Date: Fri, 23 Mar 2012 13:48:35 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: Al Viro , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] swapon: check validity of swap_flags Message-ID: User-Agent: Alpine 2.00 (LSU 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Most system calls taking flags first check that the flags passed in are valid, and that helps userspace to detect when new flags are supported. But swapon never did so: start checking now, to help if we ever want to support more swap_flags in future. It's difficult to get stray bits set in an int, and swapon is not widely used, so this is most unlikely to break any userspace; but we can just revert if it turns out to do so. Signed-off-by: Hugh Dickins --- include/linux/swap.h | 3 +++ mm/swapfile.c | 3 +++ 2 files changed, 6 insertions(+) --- linux.git/include/linux/swap.h 2012-03-23 10:19:53.408051631 -0700 +++ linux/include/linux/swap.h 2012-03-23 10:34:02.956071819 -0700 @@ -21,6 +21,9 @@ struct bio; #define SWAP_FLAG_PRIO_SHIFT 0 #define SWAP_FLAG_DISCARD 0x10000 /* discard swap cluster after use */ +#define SWAP_FLAGS_VALID (SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \ + SWAP_FLAG_DISCARD) + static inline int current_is_kswapd(void) { return current->flags & PF_KSWAPD; --- linux.git/mm/swapfile.c 2012-03-23 10:19:53.588051635 -0700 +++ linux/mm/swapfile.c 2012-03-23 10:35:52.764074181 -0700 @@ -2022,6 +2022,9 @@ SYSCALL_DEFINE2(swapon, const char __use struct page *page = NULL; struct inode *inode = NULL; + if (swap_flags & ~SWAP_FLAGS_VALID) + return -EINVAL; + if (!capable(CAP_SYS_ADMIN)) return -EPERM;