linux-kernel - Re: [PATCH v2] ARM/dma-mapping: use kvcalloc for fallback memory allocation need

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Message-ID: <Y7QBKMzuzNQAdKyY@shell.armlinux.org.uk>
Date:   Tue, 3 Jan 2023 10:19:20 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Deepak R Varma <drv@...lo.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>,
        Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Julia Lawall <julia.lawall@...ia.fr>
Subject: Re: [PATCH v2] ARM/dma-mapping: use kvcalloc for fallback memory
 allocation need

On Wed, Dec 28, 2022 at 03:49:44PM +0530, Deepak R Varma wrote:
> On Tue, Dec 20, 2022 at 07:46:32PM +0530, Deepak R Varma wrote:
> > Current conditional determination of whether to use kzalloc or vzalloc
> > has known issues such as "indefinite retry" when less than PAGE_SIZE
> > memory is needed, but is unavailable. This LWN article [1] describes
> > these issues in greater detail. Use helper function kvcalloc() instead
> > which is more efficient in terms of performance and security.
> >
> >  	[1] https://lwn.net/Articles/711653/
> >
> > This patch proposal is based on following Coccinelle warning using the
> > kvmalloc.cocci semantic patch.
> > 	arch/arm/mm/dma-mapping.c:858:28-29: WARNING opportunity for kvmalloc
> >
> > The semantic patch suggests using kvzalloc() helper function, however,
> > this patch proposes to use kvcalloc instead. kvcalloc() helper function
> > uses 2-factor argument form which is better from a security perspective
> > as described in the following KSPP project commit.
> >
> > 	Commit 4e3fd7217105 ("wireguard: ratelimiter: use kvcalloc() instead of kvzalloc()")
> >
> > Signed-off-by: Deepak R Varma <drv@...lo.com>
> 
> Hello,
> May I please request a review and feedback on this patch proposal?

The DMA API on ARM has been maintained by others recently, so it's no
longer up to me. Please include Christoph Hellwig <hch@....de> when
sending changes for this. Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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