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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id 4sm48411440pfc.92.2019.07.22.09.46.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 22 Jul 2019 09:46:07 -0700 (PDT) Date: Mon, 22 Jul 2019 09:46:06 -0700 From: Kees Cook To: Andrey Konovalov Cc: Al Viro , Eric Biederman , Linux ARM , Linux Memory Management List , LKML , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, kvm@vger.kernel.org, "open list:KERNEL SELFTEST FRAMEWORK" , Vincenzo Frascino , Will Deacon , Mark Rutland , Andrew Morton , Greg Kroah-Hartman , Yishai Hadas , Felix Kuehling , Alexander Deucher , Christian Koenig , Mauro Carvalho Chehab , Jens Wiklander , Alex Williamson , Leon Romanovsky , Luc Van Oostenryck , Dave Martin , Khalid Aziz , enh , Jason Gunthorpe , Christoph Hellwig , Dmitry Vyukov , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Robin Murphy , Kevin Brodsky , Szabolcs Nagy , Catalin Marinas Subject: Re: [PATCH v18 07/15] fs/namespace: untag user pointers in copy_mount_options Message-ID: <201907220944.5821C92518@keescook> References: <41e0a911e4e4d533486a1468114e6878e21f9f84.1561386715.git.andreyknvl@google.com> <20190624175009.GM29120@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: +Eric Biederman too, who might be able to Ack this... On Mon, Jul 15, 2019 at 06:00:04PM +0200, Andrey Konovalov wrote: > On Mon, Jun 24, 2019 at 7:50 PM Catalin Marinas wrote: > > > > On Mon, Jun 24, 2019 at 04:32:52PM +0200, Andrey Konovalov wrote: > > > This patch is a part of a series that extends kernel ABI to allow to pass > > > tagged user pointers (with the top byte set to something else other than > > > 0x00) as syscall arguments. > > > > > > In copy_mount_options a user address is being subtracted from TASK_SIZE. > > > If the address is lower than TASK_SIZE, the size is calculated to not > > > allow the exact_copy_from_user() call to cross TASK_SIZE boundary. > > > However if the address is tagged, then the size will be calculated > > > incorrectly. > > > > > > Untag the address before subtracting. > > > > > > Reviewed-by: Khalid Aziz > > > Reviewed-by: Vincenzo Frascino > > > Reviewed-by: Kees Cook > > > Reviewed-by: Catalin Marinas > > > Signed-off-by: Andrey Konovalov > > > --- > > > fs/namespace.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/fs/namespace.c b/fs/namespace.c > > > index 7660c2749c96..ec78f7223917 100644 > > > --- a/fs/namespace.c > > > +++ b/fs/namespace.c > > > @@ -2994,7 +2994,7 @@ void *copy_mount_options(const void __user * data) > > > * the remainder of the page. > > > */ > > > /* copy_from_user cannot cross TASK_SIZE ! */ > > > - size = TASK_SIZE - (unsigned long)data; > > > + size = TASK_SIZE - (unsigned long)untagged_addr(data); > > > if (size > PAGE_SIZE) > > > size = PAGE_SIZE; > > > > I think this patch needs an ack from Al Viro (cc'ed). > > > > -- > > Catalin > > Hi Al, > > Could you take a look and give your acked-by? > > Thanks! -- Kees Cook