From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751764Ab0CXVZz (ORCPT ); Wed, 24 Mar 2010 17:25:55 -0400 Received: from mail-bw0-f209.google.com ([209.85.218.209]:54515 "EHLO mail-bw0-f209.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750888Ab0CXVZx (ORCPT ); Wed, 24 Mar 2010 17:25:53 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=fw0CxAcFv5sW7hlje7Nn4sidbnGh02MphMiJ16ZUGE/WymrjnuWAk/ksBcuqKMENrx PcL7idpX0ETLDR1qCAOlBq06HzXbI9MCUr0KYZOI+sAOk5OXp8LjbQYLT6e0uEycQIPF i92nHyNgnnyXjyCt6cExap2K+OTUHgEyGhnII= Subject: Re: [PATCH] slub: Potential stack overflow From: Eric Dumazet To: Christoph Lameter Cc: Pekka J Enberg , linux-kernel In-Reply-To: References: <1269430856.3213.27.camel@edumazet-laptop> <1269458528.2849.2.camel@edumazet-laptop> <1269464591.2849.15.camel@edumazet-laptop> Content-Type: text/plain; charset="UTF-8" Date: Wed, 24 Mar 2010 22:25:47 +0100 Message-ID: <1269465947.2849.21.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le mercredi 24 mars 2010 à 16:14 -0500, Christoph Lameter a écrit : > Here is a patch for the second case. I think its better since it results > in an error display and it avoids the alloc for each slab. Add this piece > to your patch? > > Signed-off-by: Christoph Lameter Sure, here is third version : Thanks [PATCH] slub: Potential stack overflow I discovered that we can overflow stack if CONFIG_SLUB_DEBUG=y and use slabs with many objects, since list_slab_objects() and process_slab() use DECLARE_BITMAP(map, page->objects); With 65535 bits, we use 8192 bytes of stack ... Switch these allocations to dynamic allocations. Signed-off-by: Eric Dumazet Signed-off-by: Christoph Lameter --- mm/slub.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index b364844..7dc8e73 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2426,9 +2426,11 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, #ifdef CONFIG_SLUB_DEBUG void *addr = page_address(page); void *p; - DECLARE_BITMAP(map, page->objects); + long *map = kzalloc(BITS_TO_LONGS(page->objects) * sizeof(long), + GFP_ATOMIC); - bitmap_zero(map, page->objects); + if (!map) + return; slab_err(s, page, "%s", text); slab_lock(page); for_each_free_object(p, s, page->freelist) @@ -2443,6 +2445,7 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page, } } slab_unlock(page); + kfree(map); #endif } @@ -3648,10 +3651,10 @@ static int add_location(struct loc_track *t, struct kmem_cache *s, } static void process_slab(struct loc_track *t, struct kmem_cache *s, - struct page *page, enum track_item alloc) + struct page *page, enum track_item alloc, + long *map) { void *addr = page_address(page); - DECLARE_BITMAP(map, page->objects); void *p; bitmap_zero(map, page->objects); @@ -3670,11 +3673,14 @@ static int list_locations(struct kmem_cache *s, char *buf, unsigned long i; struct loc_track t = { 0, 0, NULL }; int node; + unsigned long *map = kmalloc(BITS_TO_LONGS(oo_objects(s->max)) * + sizeof(unsigned long), GFP_KERNEL); - if (!alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), - GFP_TEMPORARY)) + if (!map || !alloc_loc_track(&t, PAGE_SIZE / sizeof(struct location), + GFP_TEMPORARY)) { + kfree(map); return sprintf(buf, "Out of memory\n"); - + } /* Push back cpu slabs */ flush_all(s); @@ -3688,9 +3694,9 @@ static int list_locations(struct kmem_cache *s, char *buf, spin_lock_irqsave(&n->list_lock, flags); list_for_each_entry(page, &n->partial, lru) - process_slab(&t, s, page, alloc); + process_slab(&t, s, page, alloc, map); list_for_each_entry(page, &n->full, lru) - process_slab(&t, s, page, alloc); + process_slab(&t, s, page, alloc, map); spin_unlock_irqrestore(&n->list_lock, flags); } @@ -3741,6 +3747,7 @@ static int list_locations(struct kmem_cache *s, char *buf, } free_loc_track(&t); + kfree(map); if (!t.count) len += sprintf(buf, "No data\n"); return len;