linux-kernel - Re: [kernel-hardening] [PATCH 09/38] usercopy: Mark kmalloc caches as usercopy caches

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Date:   Mon, 3 Feb 2020 17:20:02 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Kees Cook <keescook@...omium.org>
cc:     Jann Horn <jannh@...gle.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Christoph Hellwig <hch@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Julian Wiedmann <jwi@...ux.ibm.com>,
        Ursula Braun <ubraun@...ux.ibm.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        kernel list <linux-kernel@...r.kernel.org>,
        David Windsor <dave@...lcore.net>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>, linux-xfs@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Laura Abbott <labbott@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Christoffer Dall <christoffer.dall@...aro.org>,
        Dave Kleikamp <dave.kleikamp@...cle.com>,
        Jan Kara <jack@...e.cz>,
        Luis de Bethencourt <luisbg@...nel.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Rik van Riel <riel@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [kernel-hardening] [PATCH 09/38] usercopy: Mark kmalloc caches
 as usercopy caches

On Sat, 1 Feb 2020, Kees Cook wrote:
>
> I can't find where the address limit for dma-kmalloc is implemented.

include/linux/mmzones.h

enum zone_type {
        /*
         * ZONE_DMA and ZONE_DMA32 are used when there are peripherals not able
         * to DMA to all of the addressable memory (ZONE_NORMAL).
         * On architectures where this area covers the whole 32 bit address
         * space ZONE_DMA32 is used. ZONE_DMA is left for the ones with smaller
         * DMA addressing constraints. This distinction is important as a 32bit
         * DMA mask is assumed when ZONE_DMA32 is defined. Some 64-bit
         * platforms may need both zones as they support peripherals with
         * different DMA addressing limitations.
         *
         * Some examples:
         *
         *  - i386 and x86_64 have a fixed 16M ZONE_DMA and ZONE_DMA32 for the
         *    rest of the lower 4G.
         *
         *  - arm only uses ZONE_DMA, the size, up to 4G, may vary depending on
         *    the specific device.
         *
         *  - arm64 has a fixed 1G ZONE_DMA and ZONE_DMA32 for the rest of the
         *    lower 4G.
         *
         *  - powerpc only uses ZONE_DMA, the size, up to 2G, may vary
         *    depending on the specific device.
         *
         *  - s390 uses ZONE_DMA fixed to the lower 2G.
         *
         *  - ia64 and riscv only use ZONE_DMA32.
         *
         *  - parisc uses neither.
         */
#ifdef CONFIG_ZONE_DMA
        ZONE_DMA,
#endif
#ifdef CONFIG_ZONE_DMA32
        ZONE_DMA32,
#endif
        /*
         * Normal addressable memory is in ZONE_NORMAL. DMA operations can
be
         * performed on pages in ZONE_NORMAL if the DMA devices support
         * transfers to all addressable memory.
         */
        ZONE_NORMAL,
#ifdef CONFIG_HIGHMEM
        /*
         * A memory area that is only addressable by the kernel through
         * mapping portions into its own address space. This is for example
         * used by i386 to allow the kernel to address the memory beyond
         * 900MB. The kernel will set up special mappings (page
         * table entries on i386) for each page that the kernel needs to
         * access.
         */
        ZONE_HIGHMEM,
#endif
        ZONE_MOVABLE,
#ifdef CONFIG_ZONE_DEVICE
        ZONE_DEVICE,
#endif
        __MAX_NR_ZONES

};