From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C7BEC433ED for ; Mon, 26 Apr 2021 10:28:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 25AE96120D for ; Mon, 26 Apr 2021 10:28:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232990AbhDZK3N (ORCPT ); Mon, 26 Apr 2021 06:29:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:43924 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232253AbhDZK3J (ORCPT ); Mon, 26 Apr 2021 06:29:09 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1619432906; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y+BdTlZQMIKpxwvsmFV+T7kI7pphzQZM6wgqpx86rmI=; b=OhQ8d5C9Sv6C+l4RSem6IL0d/GyiutKfHBbMofCXXOgRiJ5YmHZveWiku3dxmmiBV79FCl Mac/QHVyTjP8IEv299yylS0oqD+an5CMq8x6GY/luEunnNm1D0L4wPxLavc3QcCVEGq9y9 E7Lb3BGfaFPtJlaQq0DnFX57k0wJH9E= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 8F810B206; Mon, 26 Apr 2021 10:28:26 +0000 (UTC) Date: Mon, 26 Apr 2021 12:28:26 +0200 From: Michal Hocko To: Vasily Averin Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Alexey Dobriyan , Shakeel Butt , Johannes Weiner , Vladimir Davydov , Andrew Morton , Dmitry Safonov <0x7f454c46@gmail.com> Subject: Re: [PATCH 1/2] ipc sem: use kvmalloc for sem_undo allocation Message-ID: References: <722774d8-d46b-f8a6-a88e-3c56b4968622@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <722774d8-d46b-f8a6-a88e-3c56b4968622@virtuozzo.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 26-04-21 13:18:09, Vasily Averin wrote: > size of sem_undo can exceed one page and with the maximum possible > nsems = 32000 it can grow up to 64Kb. Let's switch its allocation > to kvmalloc to avoid user-triggered disruptive actions like OOM killer > in case of high-order memory shortage. User triggerable high order allocations are quite a problem on heavily fragmented systems. They can be a DoS vector. > Signed-off-by: Vasily Averin Acked-by: Michal Hocko > --- > ipc/sem.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/ipc/sem.c b/ipc/sem.c > index 52a6599..93088d6 100644 > --- a/ipc/sem.c > +++ b/ipc/sem.c > @@ -1152,7 +1152,7 @@ static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) > un->semid = -1; > list_del_rcu(&un->list_proc); > spin_unlock(&un->ulp->lock); > - kfree_rcu(un, rcu); > + kvfree_rcu(un, rcu); > } > > /* Wake up all pending processes and let them fail with EIDRM. */ > @@ -1935,7 +1935,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) > rcu_read_unlock(); > > /* step 2: allocate new undo structure */ > - new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, > + new = kvzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, > GFP_KERNEL_ACCOUNT); > if (!new) { > ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); > @@ -1948,7 +1948,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) > if (!ipc_valid_object(&sma->sem_perm)) { > sem_unlock(sma, -1); > rcu_read_unlock(); > - kfree(new); > + kvfree(new); > un = ERR_PTR(-EIDRM); > goto out; > } > @@ -1959,7 +1959,7 @@ static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) > */ > un = lookup_undo(ulp, semid); > if (un) { > - kfree(new); > + kvfree(new); > goto success; > } > /* step 5: initialize & link new undo structure */ > @@ -2420,7 +2420,7 @@ void exit_sem(struct task_struct *tsk) > rcu_read_unlock(); > wake_up_q(&wake_q); > > - kfree_rcu(un, rcu); > + kvfree_rcu(un, rcu); > } > kfree(ulp); > } > -- > 1.8.3.1 -- Michal Hocko SUSE Labs