Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758085Ab2EATed (ORCPT ); Tue, 1 May 2012 15:34:33 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59547 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754670Ab2EATec (ORCPT ); Tue, 1 May 2012 15:34:32 -0400 Date: Tue, 1 May 2012 12:34:30 -0700 From: Andrew Morton To: Doug Ledford Cc: linux-kernel@vger.kernel.org, sfr@canb.auug.org.au, Manfred Spraul Subject: Re: [Patch 2/4] ipc/mqueue: correct mq_attr_ok test Message-Id: <20120501123430.63f4bf85.akpm@linux-foundation.org> In-Reply-To: <4a62cbda48cf31ca796f37fa8904f314f643db57.1335894230.git.dledford@redhat.com> References: <1335894655-11398-1-git-send-email-dledford@redhat.com> <4a62cbda48cf31ca796f37fa8904f314f643db57.1335894230.git.dledford@redhat.com> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2822 Lines: 77 On Tue, 1 May 2012 13:50:53 -0400 Doug Ledford wrote: > While working on the other parts of the mqueue stuff, I noticed that > the calculation for overflow in mq_attr_ok didn't actually match > reality (this is especially true since my last patch which changed > how we account memory slightly). Please cc Manfred on mqueue things? He still watches ;) > In particular, we used to test for overflow using: > msgs * msgsize + msgs * sizeof(struct msg_msg *) > > That was never really correct because each message we allocate via > load_msg() is actually a struct msg_msg followed by the data for > the message (and if struct msg_msg + data exceeds PAGE_SIZE we end > up allocating struct msg_msgseg structs too, but accounting for them > would get really tedious, so let's ignore those...they're only a > pointer in size anyway). This patch updates the calculation to be > more accurate in regards to maximum possible memory consumption by the > mqueue. > > ... > > --- a/ipc/mqueue.c > +++ b/ipc/mqueue.c > > ... > > @@ -684,8 +686,11 @@ static int mq_attr_ok(struct ipc_namespace *ipc_ns, struct mq_attr *attr) > /* check for overflow */ > if (attr->mq_msgsize > ULONG_MAX/attr->mq_maxmsg) > return 0; > - if ((unsigned long)(attr->mq_maxmsg * (attr->mq_msgsize > - + sizeof (struct msg_msg *))) < > + mq_treesize = attr->mq_maxmsg * sizeof(struct msg_msg) + > + min_t(unsigned int, attr->mq_maxmsg, MQ_PRIO_MAX) * > + sizeof(struct posix_msg_tree_node); > + if ((unsigned long)(attr->mq_maxmsg * attr->mq_msgsize + > + mq_treesize) < > (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize)) > return 0; > return 1; That's a bit of a mouthful. Does this look OK? --- a/ipc/mqueue.c~ipc-mqueue-correct-mq_attr_ok-test-fix +++ a/ipc/mqueue.c @@ -672,7 +672,8 @@ static void remove_notification(struct m static int mq_attr_ok(struct ipc_namespace *ipc_ns, struct mq_attr *attr) { int mq_treesize; - + unsigned long total_size; + if (attr->mq_maxmsg <= 0 || attr->mq_msgsize <= 0) return 0; if (capable(CAP_SYS_RESOURCE)) { @@ -690,9 +691,8 @@ static int mq_attr_ok(struct ipc_namespa mq_treesize = attr->mq_maxmsg * sizeof(struct msg_msg) + min_t(unsigned int, attr->mq_maxmsg, MQ_PRIO_MAX) * sizeof(struct posix_msg_tree_node); - if ((unsigned long)(attr->mq_maxmsg * attr->mq_msgsize + - mq_treesize) < - (unsigned long)(attr->mq_maxmsg * attr->mq_msgsize)) + total_size = attr->mq_maxmsg * attr->mq_msgsize; + if (total_size + mq_treesize < total_size) return 0; return 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/