From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx142.postini.com [74.125.245.142]) by kanga.kvack.org (Postfix) with SMTP id B64686B0031 for ; Wed, 24 Jul 2013 20:53:03 -0400 (EDT) Message-ID: <51F076CF.2050504@huawei.com> Date: Thu, 25 Jul 2013 08:52:31 +0800 From: Libin MIME-Version: 1.0 Subject: Re: [PATCH] mm: Fix potential NULL pointer dereference References: <1374637699-25704-1-git-send-email-huawei.libin@huawei.com> <20130724114829.61EF3E0090@blue.fi.intel.com> In-Reply-To: <20130724114829.61EF3E0090@blue.fi.intel.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mgorman@suse.de, xiaoguangrong@linux.vnet.ibm.com, wujianguo@huawei.com On 2013/7/24 19:48, Kirill A. Shutemov wrote: > Libin wrote: >> find_vma may return NULL, thus check the return >> value to avoid NULL pointer dereference. >> >> Signed-off-by: Libin > > Looks correct to me. > > Acked-by: Kirill A. Shutemov > > Have you ever triggered the race or just found it by reading the code? > I wounder if it's subject for stable@. > I had not triggered the bug, although it is a small probability but it looks likely to occur. Thanks! Libin. >> --- >> mm/huge_memory.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 243e710..d4423f4 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -2294,6 +2294,8 @@ static void collapse_huge_page(struct mm_struct *mm, >> goto out; >> >> vma = find_vma(mm, address); >> + if (!vma) >> + goto out; >> hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; >> hend = vma->vm_end & HPAGE_PMD_MASK; >> if (address < hstart || address + HPAGE_PMD_SIZE > hend) >> -- >> 1.8.2.1 > -- 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