Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933743Ab0FEQvU (ORCPT ); Sat, 5 Jun 2010 12:51:20 -0400 Received: from mail-fx0-f46.google.com ([209.85.161.46]:53594 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933666Ab0FEQvT (ORCPT ); Sat, 5 Jun 2010 12:51:19 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:mime-version:content-type :content-disposition:user-agent; b=VLmWfhRSUkkRiM/bJcNaYRRftYuupkmTpA9SyznU79ZXJeLkCArBlQdVAji4QdxZ/M dsUclfSNlhFslvzz2T9mOCIe5A/Q8DqwSvy3wAIEYjSq7TLZmP8zrTRfyktqBRki1g/v dw4u7+C/Mj7TCQNVVGB185G/MmJBeHF0Rqs1I= Date: Sat, 5 Jun 2010 18:49:42 +0200 From: Marcin Slusarz To: LKML Cc: Pekka Paalanen , Stuart Bennett , Christoph Bumiller , Shinpei KATO , nouveau@lists.freedesktop.org, x86@kernel.org Subject: [PATCH] kmmio/mmiotrace: fix double free of kmmio_fault_pages Message-ID: <20100605164919.GA2816@joi.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2314 Lines: 76 After every iounmap mmiotrace has to free kmmio_fault_pages, but it can't do it directly, so it defers freeing by RCU. It usually works, but when mmiotraced code calls ioremap-iounmap multiple times without sleeping between (so RCU won't kick in and start freeing) it can be given the same virtual address, so at every iounmap mmiotrace will schedule the same pages for release. Obviously it will explode on second free. Fix it by marking kmmio_fault_pages which are scheduled for release and not adding them second time. Signed-off-by: Marcin Slusarz Cc: Pekka Paalanen Cc: Stuart Bennett --- arch/x86/mm/kmmio.c | 16 +++++++++++++--- 1 files changed, 13 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c index 5d0e67f..e5d5e2c 100644 --- a/arch/x86/mm/kmmio.c +++ b/arch/x86/mm/kmmio.c @@ -45,6 +45,8 @@ struct kmmio_fault_page { * Protected by kmmio_lock, when linked into kmmio_page_table. */ int count; + + bool scheduled_for_release; }; struct kmmio_delayed_release { @@ -398,8 +400,11 @@ static void release_kmmio_fault_page(unsigned long page, BUG_ON(f->count < 0); if (!f->count) { disarm_kmmio_fault_page(f); - f->release_next = *release_list; - *release_list = f; + if (!f->scheduled_for_release) { + f->release_next = *release_list; + *release_list = f; + f->scheduled_for_release = true; + } } } @@ -471,8 +476,10 @@ static void remove_kmmio_fault_pages(struct rcu_head *head) prevp = &f->release_next; } else { *prevp = f->release_next; + f->release_next = NULL; + f->scheduled_for_release = false; } - f = f->release_next; + f = *prevp; } spin_unlock_irqrestore(&kmmio_lock, flags); @@ -510,6 +517,9 @@ void unregister_kmmio_probe(struct kmmio_probe *p) kmmio_count--; spin_unlock_irqrestore(&kmmio_lock, flags); + if (!release_list) + return; + drelease = kmalloc(sizeof(*drelease), GFP_ATOMIC); if (!drelease) { pr_crit("leaking kmmio_fault_page objects.\n"); -- 1.7.1 -- 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/