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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id i16sm594315pfa.184.2019.10.30.11.26.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Oct 2019 11:26:11 -0700 (PDT) Date: Wed, 30 Oct 2019 11:26:10 -0700 From: Kees Cook To: Christoph Hellwig Cc: Greg Kroah-Hartman , Robin Murphy , Laura Abbott , Marek Szyprowski , Jesper Dangaard Brouer , Allison Randal , Thomas Gleixner , Stephen Boyd , Dan Carpenter , Semmle Security Reports , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/2] dma-mapping: Add vmap checks to dma_map_single() Message-ID: <201910301125.A1DD6D5F53@keescook> References: <20191029213423.28949-1-keescook@chromium.org> <20191029213423.28949-2-keescook@chromium.org> <20191030091849.GA637042@kroah.com> <20191030180921.GB19366@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191030180921.GB19366@lst.de> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 30, 2019 at 07:09:21PM +0100, Christoph Hellwig wrote: > On Wed, Oct 30, 2019 at 10:18:49AM +0100, Greg Kroah-Hartman wrote: > > On Tue, Oct 29, 2019 at 02:34:22PM -0700, Kees Cook wrote: > > > As we've seen from USB and other areas[1], we need to always do runtime > > > checks for DMA operating on memory regions that might be remapped. This > > > adds vmap checks (similar to those already in USB but missing in other > > > places) into dma_map_single() so all callers benefit from the checking. > > > > > > [1] https://git.kernel.org/linus/3840c5b78803b2b6cc1ff820100a74a092c40cbb > > > > > > Suggested-by: Laura Abbott > > > Signed-off-by: Kees Cook > > > --- > > > include/linux/dma-mapping.h | 6 ++++++ > > > 1 file changed, 6 insertions(+) > > > > > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > > > index 4a1c4fca475a..54de3c496407 100644 > > > --- a/include/linux/dma-mapping.h > > > +++ b/include/linux/dma-mapping.h > > > @@ -583,6 +583,12 @@ static inline unsigned long dma_get_merge_boundary(struct device *dev) > > > static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr, > > > size_t size, enum dma_data_direction dir, unsigned long attrs) > > > { > > > + /* DMA must never operate on areas that might be remapped. */ > > > + if (dev_WARN_ONCE(dev, is_vmalloc_addr(ptr), > > > + "wanted %zu bytes mapped in vmalloc\n", size)) { > > > + return DMA_MAPPING_ERROR; > > > + } > > > > That's a very odd error string, I know if I saw it for the first time, I > > would have no idea what it meant. The USB message at least gives you a > > bit more context as to what went wrong and how to fix it. > > > > How about something like "Memory is not DMA capabable, please fix the > > allocation of it to be correct", or "non-dma-able memory was attempted > > to be mapped, but this is impossible to to" or something else. > > I've fixed the message to "rejecting DMA map of vmalloc memory" and > applied the patch. Great; thank you! -- Kees Cook