Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932078AbbFID5A (ORCPT ); Mon, 8 Jun 2015 23:57:00 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:34099 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750814AbbFID4w (ORCPT ); Mon, 8 Jun 2015 23:56:52 -0400 Date: Tue, 9 Jun 2015 12:57:17 +0900 From: Sergey Senozhatsky To: Andrew Morton Cc: Sergey Senozhatsky , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sergey Senozhatsky , Christoph Lameter , Pekka Enberg , Joonsoo Kim , David Rientjes Subject: Re: [PATCH] zsmalloc: fix a null pointer dereference in destroy_handle_cache() Message-ID: <20150609035717.GB3297@swordfish> References: <1433502690-2524-1-git-send-email-sergey.senozhatsky@gmail.com> <20150608135532.ac913746b6394217e92a229a@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150608135532.ac913746b6394217e92a229a@linux-foundation.org> User-Agent: Mutt/1.5.23+89 (0255b37be491) (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1859 Lines: 60 On (06/08/15 13:55), Andrew Morton wrote: [..] > > zs_destroy_pool()->destroy_handle_cache() invoked from > > zs_create_pool() can pass a NULL ->handle_cachep pointer > > to kmem_cache_destroy(), which will dereference it. > > > > That's slightly lacking in details (under what circumstances will it > crash) so I changed it to > > : If zs_create_pool()->create_handle_cache()->kmem_cache_create() fails, > : zs_create_pool()->destroy_handle_cache() will dereference the NULL > : pool->handle_cachep. > : > : Modify destroy_handle_cache() to avoid this. > Oh, sorry I first received "+ zsmalloc-fix-a-null-pointer-dereference-in- destroy_handle_cache.patch added to -mm tree" message, so I replied there. fetchmail works somewhat confusing over the last weeks. > > ... > > > > --- a/mm/zsmalloc.c > > +++ b/mm/zsmalloc.c > > @@ -285,7 +285,8 @@ static int create_handle_cache(struct zs_pool *pool) > > > > static void destroy_handle_cache(struct zs_pool *pool) > > { > > - kmem_cache_destroy(pool->handle_cachep); > > + if (pool->handle_cachep) > > + kmem_cache_destroy(pool->handle_cachep); > > } > > > > static unsigned long alloc_handle(struct zs_pool *pool) > > I'll apply this, but... from a bit of grepping I'm estimating that we > have approximately 200 instances of > > if (foo) > kmem_cache_destroy(foo); > > so obviously kmem_cache_destroy() should be doing the check. Yes, I thought about this. A naive grepping gave me 563 occurrences git grep kmem_cache_destroy | wc -l 563 So I decided to hold this activity. Well, I think I can create this patch bomb, it's trivial. -ss -- 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/