Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761465AbaJDAws (ORCPT ); Fri, 3 Oct 2014 20:52:48 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:44722 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754324AbaJCVcd (ORCPT ); Fri, 3 Oct 2014 17:32:33 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tetsuo Handa , Dave Airlie Subject: [PATCH 3.16 015/357] drm/ttm: Fix possible stack overflow by recursive shrinker calls. Date: Fri, 3 Oct 2014 14:26:41 -0700 Message-Id: <20141003212933.930837412@linuxfoundation.org> X-Mailer: git-send-email 2.1.2 In-Reply-To: <20141003212933.458851516@linuxfoundation.org> References: <20141003212933.458851516@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tetsuo Handa commit 71336e011d1d2312bcbcaa8fcec7365024f3a95d upstream. While ttm_dma_pool_shrink_scan() tries to take mutex before doing GFP_KERNEL allocation, ttm_pool_shrink_scan() does not do it. This can result in stack overflow if kmalloc() in ttm_page_pool_free() triggered recursion due to memory pressure. shrink_slab() => ttm_pool_shrink_scan() => ttm_page_pool_free() => kmalloc(GFP_KERNEL) => shrink_slab() => ttm_pool_shrink_scan() => ttm_page_pool_free() => kmalloc(GFP_KERNEL) Change ttm_pool_shrink_scan() to do like ttm_dma_pool_shrink_scan() does. Signed-off-by: Tetsuo Handa Signed-off-by: Dave Airlie Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/ttm/ttm_page_alloc.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/drivers/gpu/drm/ttm/ttm_page_alloc.c +++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c @@ -391,14 +391,17 @@ out: static unsigned long ttm_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) { - static atomic_t start_pool = ATOMIC_INIT(0); + static DEFINE_MUTEX(lock); + static unsigned start_pool; unsigned i; - unsigned pool_offset = atomic_add_return(1, &start_pool); + unsigned pool_offset; struct ttm_page_pool *pool; int shrink_pages = sc->nr_to_scan; unsigned long freed = 0; - pool_offset = pool_offset % NUM_POOLS; + if (!mutex_trylock(&lock)) + return SHRINK_STOP; + pool_offset = ++start_pool % NUM_POOLS; /* select start pool in round robin fashion */ for (i = 0; i < NUM_POOLS; ++i) { unsigned nr_free = shrink_pages; @@ -408,6 +411,7 @@ ttm_pool_shrink_scan(struct shrinker *sh shrink_pages = ttm_page_pool_free(pool, nr_free); freed += nr_free - shrink_pages; } + mutex_unlock(&lock); return freed; } -- 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/