Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759023Ab2HWOld (ORCPT ); Thu, 23 Aug 2012 10:41:33 -0400 Received: from mx2.parallels.com ([64.131.90.16]:50598 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757928Ab2HWOlb (ORCPT ); Thu, 23 Aug 2012 10:41:31 -0400 Message-ID: <5036405D.1060204@parallels.com> Date: Thu, 23 Aug 2012 18:38:21 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Michal Hocko CC: , Andrew Morton , , Peter Zijlstra Subject: Re: [PATCH] fork: fix oops after fork failure References: <1345727326-18730-1-git-send-email-glommer@parallels.com> <20120823143312.GA23636@dhcp22.suse.cz> In-Reply-To: <20120823143312.GA23636@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2079 Lines: 50 On 08/23/2012 06:33 PM, Michal Hocko wrote: > On Thu 23-08-12 17:08:46, Glauber Costa wrote: >> When we want to duplicate a new process, dup_task_struct() will undergo >> a series of allocations. If alloc_thread_info_node() fails, we call >> free_task_struct() and return. >> >> This seems right, but it is not. free_task_struct() will not only free >> the task struct from the kmem_cache, but will also call >> arch_release_task_struct(). The problem is that this function is >> supposed to undo whatever arch-specific work done by >> arch_dup_task_struct(), that is not yet called at this point. The >> particular problem I ran accross was that in x86, we will arrive at >> fpu_free() without having ever allocated it. >> >> This code is very ancient, and according to git, it is there since the >> pre-git era. But forks don't fail that often, so that made it well >> hidden. >> >> Signed-off-by: Glauber Costa >> Reported-by: Frederic Weisbecker >> --- >> kernel/fork.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/fork.c b/kernel/fork.c >> index 152d023..b397435 100644 >> --- a/kernel/fork.c >> +++ b/kernel/fork.c >> @@ -299,7 +299,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig) >> >> ti = alloc_thread_info_node(tsk, node); >> if (!ti) { >> - free_task_struct(tsk); >> + kmem_cache_free(task_struct_cachep, tsk); > > What about ia64 (or !CONFIG_ARCH_THREAD_INFO_ALLOCATOR in general) which > doesn't allocate thread_info at all? They would return something meaningful here anyway, otherwise this would already error out and exit. But you actually have a point. Not all architectures (all but ia64) will allocathe the task struct from the slab... sigh... Sorry, I will come up with something for this. -- 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/