Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753696Ab3CAUSa (ORCPT ); Fri, 1 Mar 2013 15:18:30 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:51458 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752737Ab3CATpa (ORCPT ); Fri, 1 Mar 2013 14:45:30 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro , Sakari Ailus , Laurent Pinchart , Archit Taneja , Prabhakar Lad , Mauro Carvalho Chehab Subject: [ 46/77] media: omap_vout: find_vma() needs ->mmap_sem held Date: Fri, 1 Mar 2013 11:44:31 -0800 Message-Id: <20130301194356.840788893@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130301194351.913471337@linuxfoundation.org> References: <20130301194351.913471337@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2722 Lines: 69 3.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro commit 55ee64b30a38d688232e5eb2860467dddc493573 upstream. Walking rbtree while it's modified is a Bad Idea(tm); besides, the result of find_vma() can be freed just as it's getting returned to caller. Fortunately, it's easy to fix - just take ->mmap_sem a bit earlier (and don't bother with find_vma() at all if virtp >= PAGE_OFFSET - in that case we don't even look at its result). While we are at it, what prevents VIDIOC_PREPARE_BUF calling v4l_prepare_buf() -> (e.g) vb2_ioctl_prepare_buf() -> vb2_prepare_buf() -> __buf_prepare() -> __qbuf_userptr() -> vb2_vmalloc_get_userptr() -> find_vma(), AFAICS without having taken ->mmap_sem anywhere in process? The code flow is bloody convoluted and depends on a bunch of things done by initialization, so I certainly might've missed something... Signed-off-by: Al Viro Cc: Sakari Ailus Cc: Laurent Pinchart Cc: Archit Taneja Cc: Prabhakar Lad Signed-off-by: Mauro Carvalho Chehab Signed-off-by: Greg Kroah-Hartman --- drivers/media/platform/omap/omap_vout.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/drivers/media/platform/omap/omap_vout.c +++ b/drivers/media/platform/omap/omap_vout.c @@ -205,19 +205,21 @@ static u32 omap_vout_uservirt_to_phys(u3 struct vm_area_struct *vma; struct mm_struct *mm = current->mm; - vma = find_vma(mm, virtp); /* For kernel direct-mapped memory, take the easy way */ - if (virtp >= PAGE_OFFSET) { - physp = virt_to_phys((void *) virtp); - } else if (vma && (vma->vm_flags & VM_IO) && vma->vm_pgoff) { + if (virtp >= PAGE_OFFSET) + return virt_to_phys((void *) virtp); + + down_read(¤t->mm->mmap_sem); + vma = find_vma(mm, virtp); + if (vma && (vma->vm_flags & VM_IO) && vma->vm_pgoff) { /* this will catch, kernel-allocated, mmaped-to-usermode addresses */ physp = (vma->vm_pgoff << PAGE_SHIFT) + (virtp - vma->vm_start); + up_read(¤t->mm->mmap_sem); } else { /* otherwise, use get_user_pages() for general userland pages */ int res, nr_pages = 1; struct page *pages; - down_read(¤t->mm->mmap_sem); res = get_user_pages(current, current->mm, virtp, nr_pages, 1, 0, &pages, NULL); -- 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/