Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758617Ab3IYBly (ORCPT ); Tue, 24 Sep 2013 21:41:54 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:38523 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755071Ab3IYAIa (ORCPT ); Tue, 24 Sep 2013 20:08:30 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Libin , "Kirill A. Shutemov" , Wanpeng Li , Michal Hocko , Andrew Morton , Linus Torvalds Subject: [ 24/28] mm/huge_memory.c: fix potential NULL pointer dereference Date: Tue, 24 Sep 2013 17:07:55 -0700 Message-Id: <20130925000654.152727471@linuxfoundation.org> X-Mailer: git-send-email 1.8.4.3.gca3854a In-Reply-To: <20130925000648.404447782@linuxfoundation.org> References: <20130925000648.404447782@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1579 Lines: 48 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Libin commit a8f531ebc33052642b4bd7b812eedf397108ce64 upstream. In collapse_huge_page() there is a race window between releasing the mmap_sem read lock and taking the mmap_sem write lock, so find_vma() may return NULL. So check the return value to avoid NULL pointer dereference. collapse_huge_page khugepaged_alloc_page up_read(&mm->mmap_sem) down_write(&mm->mmap_sem) vma = find_vma(mm, address) Signed-off-by: Libin Acked-by: Kirill A. Shutemov Reviewed-by: Wanpeng Li Reviewed-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/huge_memory.c | 2 ++ 1 file changed, 2 insertions(+) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1838,6 +1838,8 @@ static void collapse_huge_page(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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/