Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933422AbZFOSDw (ORCPT ); Mon, 15 Jun 2009 14:03:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932422AbZFOSA4 (ORCPT ); Mon, 15 Jun 2009 14:00:56 -0400 Received: from moodiegate.xandros.com ([142.46.212.62]:51985 "EHLO dactyl.ottawa.xandros.ca" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932835AbZFOSAz (ORCPT ); Mon, 15 Jun 2009 14:00:55 -0400 X-Greylist: delayed 2956 seconds by postgrey-1.27 at vger.kernel.org; Mon, 15 Jun 2009 14:00:55 EDT From: Zygo Blaxell Date: Fri, 12 Jun 2009 13:37:50 -0400 Subject: [PATCH] LIB: remove unmatched write_lock() in gen_pool_destroy To: linux-kernel@vger.kernel.org, trivial@kernel.org Message-Id: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1872 Lines: 45 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 -- 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/