From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx191.postini.com [74.125.245.191]) by kanga.kvack.org (Postfix) with SMTP id 105076B006C for ; Tue, 27 Nov 2012 16:39:55 -0500 (EST) From: Naoya Horiguchi Subject: Re: [PATCH] mm, soft offline: split thp at the beginning of soft_offline_page() Date: Tue, 27 Nov 2012 16:39:41 -0500 Message-Id: <1354052381-28687-1-git-send-email-n-horiguchi@ah.jp.nec.com> In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Andi Kleen Cc: Naoya Horiguchi , Andrew Morton , Tony Luck , Andi Kleen , Wu Fengguang , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org On Tue, Nov 27, 2012 at 01:08:38PM -0800, Andi Kleen wrote: > Naoya Horiguchi writes: > > > When we try to soft-offline a thp tail page, put_page() is called on the > > tail page unthinkingly and VM_BUG_ON is triggered in put_compound_page(). > > This patch splits thp before going into the main body of soft-offlining. > > Looks good. > > > > > The interface of soft-offlining is open for userspace, so this bug can > > lead to DoS attack and should be fixed immedately. > > The interface is root only and root can do everything anyways, so it's > not really a security issue. OK, this description had better not be here. I replace with attached one. (.. and I forgot to disable suppress-cc for stable@vger.kernel.org in the initial post so did it now, sorry.) --- From: Naoya Horiguchi Date: Tue, 27 Nov 2012 15:38:23 -0500 Subject: [PATCH] mm, soft offline: split thp at the beginning of soft_offline_page() When we try to soft-offline a thp tail page, put_page() is called on the tail page unthinkingly and VM_BUG_ON is triggered in put_compound_page(). This patch splits thp before going into the main body of soft-offlining. Signed-off-by: Naoya Horiguchi Cc: stable@vger.kernel.org --- mm/memory-failure.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 8fe3640..e48e235 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1548,9 +1548,17 @@ int soft_offline_page(struct page *page, int flags) { int ret; unsigned long pfn = page_to_pfn(page); + struct page *hpage = compound_trans_head(page); if (PageHuge(page)) return soft_offline_huge_page(page, flags); + if (PageTransHuge(hpage)) { + if (PageAnon(hpage) && unlikely(split_huge_page(hpage))) { + pr_info("soft offline: %#lx: failed to split THP\n", + pfn); + return -EBUSY; + } + } ret = get_any_page(page, pfn, flags); if (ret < 0) -- 1.7.11.7 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org