Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935722AbZFOVfm (ORCPT ); Mon, 15 Jun 2009 17:35:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934528AbZFOVfe (ORCPT ); Mon, 15 Jun 2009 17:35:34 -0400 Received: from cantor.suse.de ([195.135.220.2]:52515 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933185AbZFOVfd (ORCPT ); Mon, 15 Jun 2009 17:35:33 -0400 Date: Mon, 15 Jun 2009 23:35:31 +0200 (CEST) From: Jiri Kosina X-X-Sender: jkosina@wotan.suse.de To: Zygo Blaxell Cc: linux-kernel@vger.kernel.org, Steve Wise , Andrew Morton Subject: Re: [PATCH] LIB: remove unmatched write_lock() in gen_pool_destroy In-Reply-To: Message-ID: References: User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) 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 Content-Length: 2150 Lines: 59 On Fri, 12 Jun 2009, Zygo Blaxell wrote: > Fix mismatch between calls to write_lock() and write_unlock() in > gen_pool_destroy by removing the write_lock(). > > Signed-off-by: Zygo Blaxell > --- > There is a call to write_lock() in gen_pool_destroy which is not balanced > by any corresponding write_unlock(). This causes problems with preemption > because the preemption-disable counter is incremented in the write_lock() > call, but never decremented by any call to write_unlock(). This bug is > difficult to observe in the field because only two in-tree drivers call > gen_pool_destroy, and one of them is non-x86 arch-specific code. > > To fix this, I have chosen removing the write_lock() over adding a > write_unlock() because the lock in question is inside a structure which > is being freed. Any other thread that waited to acquire such a lock > while gen_pool_destroy was running would find itself holding a lock > in recently-freed or about-to-be-freed memory. This would result in > memory corruption or a crash whether &pool->lock is held or not. > > Using a pool while it is in the process of being destroyed is a bug that > must be resolved outside of the gen_pool_destroy function. > > lib/genalloc.c | 1 - > 1 files changed, 0 insertions(+), 1 deletions(-) > > diff --git a/lib/genalloc.c b/lib/genalloc.c > index f6d276d..eed2bdb 100644 > --- a/lib/genalloc.c > +++ b/lib/genalloc.c > @@ -85,7 +85,6 @@ void gen_pool_destroy(struct gen_pool *pool) > int bit, end_bit; > > > - write_lock(&pool->lock); > list_for_each_safe(_chunk, _next_chunk, &pool->chunks) { > chunk = list_entry(_chunk, struct gen_pool_chunk, next_chunk); > list_del(&chunk->next_chunk); > -- > 1.5.6.5 > Hi Zygo, this doesn't really qualify for trivial tree, as it introduces a significant code change. Adding some CCs. Thanks, -- Jiri Kosina SUSE Labs -- 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/