From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754421Ab0CYT3L (ORCPT ); Thu, 25 Mar 2010 15:29:11 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:41222 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754139Ab0CYT3J (ORCPT ); Thu, 25 Mar 2010 15:29:09 -0400 Message-ID: <4BABB982.7070906@cs.helsinki.fi> Date: Thu, 25 Mar 2010 21:29:06 +0200 From: Pekka Enberg User-Agent: Thunderbird 2.0.0.24 (Macintosh/20100228) MIME-Version: 1.0 To: Eric Dumazet CC: Christoph Lameter , linux-kernel Subject: Re: [PATCH] slub: Potential stack overflow References: <1269430856.3213.27.camel@edumazet-laptop> <1269458528.2849.2.camel@edumazet-laptop> <1269464591.2849.15.camel@edumazet-laptop> <1269465947.2849.21.camel@edumazet-laptop> In-Reply-To: <1269465947.2849.21.camel@edumazet-laptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Eric Dumazet wrote: > 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 : Christoph, does this look OK to you? I think Eric has all your later additions and kfree() fixlets here. > [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; > >