Re: [PATCH 5.10 1/1] Reinstate some of "swiotlb: rework "fix info leak with DMA_FROM_DEVICE""

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, May 23, 2022 at 02:40:08PM +0300, Ovidiu Panait wrote:
> From: Linus Torvalds <torvalds@linux-foundation.org>
> 
> commit 901c7280ca0d5e2b4a8929fbe0bfb007ac2a6544 upstream.
> 
> Halil Pasic points out [1] that the full revert of that commit (revert
> in bddac7c1e02b), and that a partial revert that only reverts the
> problematic case, but still keeps some of the cleanups is probably
> better.  
> 
> And that partial revert [2] had already been verified by Oleksandr
> Natalenko to also fix the issue, I had just missed that in the long
> discussion.
> 
> So let's reinstate the cleanups from commit aa6f8dcbab47 ("swiotlb:
> rework "fix info leak with DMA_FROM_DEVICE""), and effectively only
> revert the part that caused problems.
> 
> Link: https://lore.kernel.org/all/20220328013731.017ae3e3.pasic@linux.ibm.com/ [1]
> Link: https://lore.kernel.org/all/20220324055732.GB12078@lst.de/ [2]
> Link: https://lore.kernel.org/all/4386660.LvFx2qVVIh@natalenko.name/ [3]
> Suggested-by: Halil Pasic <pasic@linux.ibm.com>
> Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> [OP: backport to 5.10: adjusted context]
> Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
> ---
> This is part of CVE-2022-0854 patchset:
> [1] ddbd89deb7d3 ("swiotlb: fix info leak with DMA_FROM_DEVICE")
> [2] 901c7280ca0d ("Reinstate some of "swiotlb: rework "fix info leak with DMA_FROM_DEVICE""")
> 
> [1] is already present in 5.10-stable.
> [2] is present in 5.17/5.16/5.15, but not in 5.10 and 5.4 branches;
> 
>  Documentation/core-api/dma-attributes.rst |  8 --------
>  include/linux/dma-mapping.h               |  8 --------
>  kernel/dma/swiotlb.c                      | 12 ++++++++----
>  3 files changed, 8 insertions(+), 20 deletions(-)

This looks much different than the backport Sasha did.  I'll drop his
and review all of this after this next round of -rc releases go out.

thanks,

greg k-h