From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753569AbeDSV1I (ORCPT ); Thu, 19 Apr 2018 17:27:08 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:33574 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753443AbeDSV1H (ORCPT ); Thu, 19 Apr 2018 17:27:07 -0400 Date: Thu, 19 Apr 2018 17:27:06 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: "Michael S. Tsirkin" cc: David Miller , Andrew Morton , linux-mm@kvack.org, eric.dumazet@gmail.com, edumazet@google.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, jasowang@redhat.com, virtualization@lists.linux-foundation.org, dm-devel@redhat.com, Vlastimil Babka Subject: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG In-Reply-To: <20180419193554-mutt-send-email-mst@kernel.org> Message-ID: References: <3e65977e-53cd-bf09-bc4b-0ce40e9091fe@gmail.com> <20180418.134651.2225112489265654270.davem@davemloft.net> <20180419193554-mutt-send-email-mst@kernel.org> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 19 Apr 2018, Michael S. Tsirkin wrote: > Maybe make it conditional on CONFIG_DEBUG_SG too? > Otherwise I think you just trigger a hard to debug memory corruption. OK, here I resend the patch with CONFIG_DEBUG_SG. With CONFIG_DEBUG_SG, the DMA API will print a stacktrace where the misuse happened, so it's much easier to debug than with CONFIG_DEBUG_VM. Fedora doesn't use CONFIG_DEBUG_SG in its default kernel (it only uses it in the debugging kernel), so users won't be hurt by this. From: Mikulas Patocka Subject: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG The kvmalloc function tries to use kmalloc and falls back to vmalloc if kmalloc fails. Unfortunatelly, some kernel code has bugs - it uses kvmalloc and then uses DMA-API on the returned memory or frees it with kfree. Such bugs were found in the virtio-net driver, dm-integrity or RHEL7 powerpc-specific code. These bugs are hard to reproduce because vmalloc falls back to kmalloc only if memory is fragmented. In order to detect these bugs reliably I submit this patch that changes kvmalloc to always use vmalloc if CONFIG_DEBUG_SG is turned on. Signed-off-by: Mikulas Patocka --- mm/util.c | 2 ++ 1 file changed, 2 insertions(+) Index: linux-2.6/mm/util.c =================================================================== --- linux-2.6.orig/mm/util.c 2018-04-18 15:46:23.000000000 +0200 +++ linux-2.6/mm/util.c 2018-04-19 23:14:14.000000000 +0200 @@ -395,6 +395,7 @@ EXPORT_SYMBOL(vm_mmap); */ void *kvmalloc_node(size_t size, gfp_t flags, int node) { +#ifndef CONFIG_DEBUG_SG gfp_t kmalloc_flags = flags; void *ret; @@ -426,6 +427,7 @@ void *kvmalloc_node(size_t size, gfp_t f */ if (ret || size <= PAGE_SIZE) return ret; +#endif return __vmalloc_node_flags_caller(size, node, flags, __builtin_return_address(0));