From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx131.postini.com [74.125.245.131]) by kanga.kvack.org (Postfix) with SMTP id 2A8AE6B0031 for ; Thu, 25 Jul 2013 21:17:28 -0400 (EDT) Message-ID: <51F1CE0B.7070502@huawei.com> Date: Fri, 26 Jul 2013 09:16:59 +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> <20130724042208.GJ22680@hacker.(null)> <20130724043531.GA22357@hacker.(null)> In-Reply-To: <20130724043531.GA22357@hacker.(null)> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Wanpeng Li Cc: 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 2013/7/24 12:35, Wanpeng Li wrote: > 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. > Yes, In khugepaged_alloc_page mmap_sem read lock was released. Thanks for your reply. Libin. >>> 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