From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx202.postini.com [74.125.245.202]) by kanga.kvack.org (Postfix) with SMTP id 776616B0031 for ; Wed, 24 Jul 2013 00:35:39 -0400 (EDT) Received: from /spool/local by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 24 Jul 2013 09:59:51 +0530 Received: from d28relay03.in.ibm.com (d28relay03.in.ibm.com [9.184.220.60]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 737BD394002D for ; Wed, 24 Jul 2013 10:05:28 +0530 (IST) Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay03.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r6O4aPDH42729572 for ; Wed, 24 Jul 2013 10:06:25 +0530 Received: from d28av05.in.ibm.com (loopback [127.0.0.1]) by d28av05.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r6O4ZWTm029368 for ; Wed, 24 Jul 2013 14:35:33 +1000 Date: Wed, 24 Jul 2013 12:35:31 +0800 From: Wanpeng Li Subject: Re: [PATCH] mm: Fix potential NULL pointer dereference Message-ID: <20130724043531.GA22357@hacker.(null)> Reply-To: Wanpeng Li References: <1374637699-25704-1-git-send-email-huawei.libin@huawei.com> <20130724042208.GJ22680@hacker.(null)> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130724042208.GJ22680@hacker.(null)> Sender: owner-linux-mm@kvack.org List-ID: To: Wanpeng Li Cc: Libin , linux-mm@kvack.org, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, mgorman@suse.de, xiaoguangrong@linux.vnet.ibm.com, wujianguo@huawei.com On Wed, Jul 24, 2013 at 12:22:08PM +0800, Wanpeng Li wrote: >On Wed, Jul 24, 2013 at 11:48:19AM +0800, Libin wrote: >>find_vma may return NULL, thus check the return >>value to avoid NULL pointer dereference. >> > >When can this happen since down_read(&mm->mmap_sem) is held? > Between mmap_sem read lock released and write lock held I think. >>Signed-off-by: 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 > >-- >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 -- 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