From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1as6G4-0007Az-D1 for kexec@lists.infradead.org; Mon, 18 Apr 2016 10:18:20 +0000 Date: Mon, 18 Apr 2016 18:17:56 +0800 From: Baoquan He Subject: Re: [PATCH 2/3] kexec: ensure user memory sizes do not wrap Message-ID: <20160418101756.GD3602@x1.redhat.com> References: <20160414195938.GV19428@n2100.arm.linux.org.uk> <20160418053534.GB3602@x1.redhat.com> <20160418083715.GZ19428@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160418083715.GZ19428@n2100.arm.linux.org.uk> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Russell King - ARM Linux Cc: Fenghua Yu , Tony Luck , linux-ia64@vger.kernel.org, Eric Biederman , kexec@lists.infradead.org On 04/18/16 at 09:37am, Russell King - ARM Linux wrote: > On Mon, Apr 18, 2016 at 01:35:34PM +0800, Baoquan He wrote: > > On 04/14/16 at 09:00pm, Russell King wrote: > > > Ensure that user memory sizes do not wrap around when validating the > > > user input, which can lead to the following input validation working > > > incorrectly. > > > > > > Signed-off-by: Russell King > > > --- > > > kernel/kexec_core.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c > > > index 8d34308ea449..d719a4d0ef55 100644 > > > --- a/kernel/kexec_core.c > > > +++ b/kernel/kexec_core.c > > > @@ -169,6 +169,8 @@ int sanity_check_segment_list(struct kimage *image) > > > > > > mstart = image->segment[i].mem; > > > mend = mstart + image->segment[i].memsz; > > > + if (mstart > mend) > > > + return result; > > > > These segments are built in kexec utility, their availability should be > > guaranteed there. If without some alignment handling, wrapping around > > might not happen here. But I don't have strong objection to it. > > In which case, what's the point of all the other validation which is done, > like the check below: > > > > if ((mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK)) > > > return result; > > > if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT) > > Your reply is contradictory to the whole suite of tests which kexec does > to validate its input from userspace. It's not contradictory. In kexec utility it will call valid_memory_segment() to check each segment. And there it will check if the start is bigger than end. What I meant is if start is 5000, end is 5100, an alignment of end will make start> end case happen. Anyway I am fine with this check adding, the safer, the better. > > -- > RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ > FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up > according to speedtest.net. > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec