All of lore.kernel.org
 help / color / mirror / Atom feed
From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Igor Klochko <igor.klochko@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
	iommu@lists.linux.dev, robin.murphy@arm.com,
	m.szyprowski@samsung.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arch/arm/mm/dma-mapping.c: fix __alloc_from_pool returning a dirty buffer
Date: Tue, 3 Jan 2023 09:51:09 +0000	[thread overview]
Message-ID: <Y7P6jeHCoTVRhl7X@shell.armlinux.org.uk> (raw)
In-Reply-To: <43ef46fc-2fbc-31b7-d683-f7496b39dae5@gmail.com>

On Fri, Dec 23, 2022 at 11:51:43PM +0100, Igor Klochko wrote:
> Thanks Christoph,
> 
> Added fixes and a changelog.
> This issue is present in all current LTS versions.
> 
> ----
> Buffers allocated by __alloc_from_pool() should be zeroed out as done by other allocators.
> Certain drivers expect a clean buffer and clearing the buffer is beneficial from the security point of view.
> ---
> Fixes: 36d0fd2198da3 (*arm: use genalloc for the atomic pool*)
> Signed-off-by: Igor Klochko <igor.klochko@gmail.com>
> ---
>  arch/arm/mm/dma-mapping.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index c135f6e37a00..bb2bb3ab497a 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -366,6 +366,7 @@ static void *__alloc_from_pool(size_t size, struct page **ret_page)
>  
>  		*ret_page = phys_to_page(phys);
>  		ptr = (void *)val;
> +		memset(ptr, 0, size);

I'm not up to speed with the current structure of the DMA implementation
on ARM, but isn't this going to make cache lines dirty for the returned
buffer, which will corrupt DMA on non-coherent devices?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

WARNING: multiple messages have this Message-ID (diff)
From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Igor Klochko <igor.klochko@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
	iommu@lists.linux.dev, robin.murphy@arm.com,
	m.szyprowski@samsung.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arch/arm/mm/dma-mapping.c: fix __alloc_from_pool returning a dirty buffer
Date: Tue, 3 Jan 2023 09:51:09 +0000	[thread overview]
Message-ID: <Y7P6jeHCoTVRhl7X@shell.armlinux.org.uk> (raw)
In-Reply-To: <43ef46fc-2fbc-31b7-d683-f7496b39dae5@gmail.com>

On Fri, Dec 23, 2022 at 11:51:43PM +0100, Igor Klochko wrote:
> Thanks Christoph,
> 
> Added fixes and a changelog.
> This issue is present in all current LTS versions.
> 
> ----
> Buffers allocated by __alloc_from_pool() should be zeroed out as done by other allocators.
> Certain drivers expect a clean buffer and clearing the buffer is beneficial from the security point of view.
> ---
> Fixes: 36d0fd2198da3 (*arm: use genalloc for the atomic pool*)
> Signed-off-by: Igor Klochko <igor.klochko@gmail.com>
> ---
>  arch/arm/mm/dma-mapping.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index c135f6e37a00..bb2bb3ab497a 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -366,6 +366,7 @@ static void *__alloc_from_pool(size_t size, struct page **ret_page)
>  
>  		*ret_page = phys_to_page(phys);
>  		ptr = (void *)val;
> +		memset(ptr, 0, size);

I'm not up to speed with the current structure of the DMA implementation
on ARM, but isn't this going to make cache lines dirty for the returned
buffer, which will corrupt DMA on non-coherent devices?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2023-01-03 10:01 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-23 14:15 [PATCH] arch/arm/mm/dma-mapping.c: fix __alloc_from_pool returning a dirty buffer Igor Klochko
2022-12-23 14:39 ` Christoph Hellwig
2022-12-23 22:51   ` Igor Klochko
2022-12-23 22:51     ` Igor Klochko
2023-01-03  9:51     ` Russell King (Oracle) [this message]
2023-01-03  9:51       ` Russell King (Oracle)
2023-01-03 13:58       ` Robin Murphy
2023-01-03 13:58         ` Robin Murphy

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Y7P6jeHCoTVRhl7X@shell.armlinux.org.uk \
    --to=linux@armlinux.org.uk \
    --cc=hch@lst.de \
    --cc=igor.klochko@gmail.com \
    --cc=iommu@lists.linux.dev \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=m.szyprowski@samsung.com \
    --cc=robin.murphy@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.