From: Christoph Hellwig <hch@infradead.org>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>,
Michal Nazarewicz <mina86@mina86.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH] mm: cma: honor __GFP_ZERO flag in cma_alloc()
Date: Wed, 13 Jun 2018 05:52:42 -0700 [thread overview]
Message-ID: <20180613125242.GA32016@infradead.org> (raw)
In-Reply-To: <20180613085851eucas1p20337d050face8ff8ea87674e16a9ccd2~3rI_9nj8b0455904559eucas1p2C@eucas1p2.samsung.com>
On Wed, Jun 13, 2018 at 10:58:37AM +0200, Marek Szyprowski wrote:
> cma_alloc() function has gfp mask parameter, so users expect that it
> honors typical memory allocation related flags. The most imporant from
> the security point of view is handling of __GFP_ZERO flag, because memory
> allocated by this function usually can be directly remapped to userspace
> by device drivers as a part of multimedia processing and ignoring this
> flag might lead to leaking some kernel structures to userspace.
> Some callers of this function (for example arm64 dma-iommu glue code)
> already assumed that the allocated buffers are cleared when this flag
> is set. To avoid such issues, add simple code for clearing newly
> allocated buffer when __GFP_ZERO flag is set. Callers will be then
> updated to skip implicit clearing or adjust passed gfp flags.
dma mapping implementations need to zero all memory returned anyway
(even if a few implementation don't do that yet).
I'd rather keep the zeroing in the common callers.
prev parent reply other threads:[~2018-06-13 12:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20180613085851eucas1p20337d050face8ff8ea87674e16a9ccd2@eucas1p2.samsung.com>
2018-06-13 8:58 ` [PATCH] mm: cma: honor __GFP_ZERO flag in cma_alloc() Marek Szyprowski
2018-06-13 12:24 ` Matthew Wilcox
2018-06-13 12:40 ` Marek Szyprowski
2018-06-13 12:55 ` Christoph Hellwig
2018-06-13 13:39 ` Michal Hocko
2018-07-02 13:23 ` Marek Szyprowski
2018-07-02 13:30 ` Christoph Hellwig
2018-07-09 10:32 ` Marek Szyprowski
2018-07-02 13:32 ` Michal Hocko
2018-07-09 10:31 ` Marek Szyprowski
2018-06-13 12:52 ` Christoph Hellwig [this message]
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