From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id D2DDD8D0039 for ; Thu, 3 Feb 2011 15:51:05 -0500 (EST) Date: Thu, 3 Feb 2011 21:50:04 +0100 (CET) From: Jesper Juhl Subject: [PATCH] Huge TLB: Potential NULL deref in arch/x86/mm/hugetlbpage.c:huge_pmd_share() Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, linux-mm@kvack.org, Tejun Heo , "H. Peter Anvin" , Ingo Molnar , Thomas Gleixner , Rohit Seth , Andrew Morton In arch/x86/mm/hugetlbpage.c:huge_pmd_share() we call find_vma(mm, addr) and then subsequently dereference the pointer returned without checking if it was NULL. I can't find anything that guarantees that find_vma() will never return NULL in this case, so I believe there's a genuine bug. However, I'd greatly appreciate it if someone would take the time to double check me. This patch implements what I believe to be the correct handling of a NULL return from find_vma(). Please consider for inclusion. Signed-off-by: Jesper Juhl --- hugetlbpage.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c index 069ce7c..0ebd3d0 100644 --- a/arch/x86/mm/hugetlbpage.c +++ b/arch/x86/mm/hugetlbpage.c @@ -61,14 +61,19 @@ static int vma_shareable(struct vm_area_struct *vma, unsigned long addr) static void huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) { struct vm_area_struct *vma = find_vma(mm, addr); - struct address_space *mapping = vma->vm_file->f_mapping; - pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + - vma->vm_pgoff; + struct address_space *mapping; + pgoff_t idx; struct prio_tree_iter iter; struct vm_area_struct *svma; unsigned long saddr; pte_t *spte = NULL; + if (!vma) + return; + + mapping = vma->vm_file->f_mapping; + idx = ((addr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; + if (!vma_shareable(vma, addr)) return; -- Jesper Juhl http://www.chaosbits.net/ Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org