linux-kernel - Re: [PATCH] swiotlb: add overflow checks to swiotlb

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Date:   Tue, 13 Jul 2021 19:54:12 -0400
From:   Konrad Rzeszutek Wilk <konrad@...nok.org>
To:     Dominique Martinet <dominique.martinet@...ark-techno.com>
Cc:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        linux-kernel@...r.kernel.org,
        Bumyong Lee <bumyong.lee@...sung.com>,
        iommu@...ts.linux-foundation.org,
        Chanho Park <chanho61.park@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] swiotlb: add overflow checks to swiotlb_bounce

On Wed, Jul 07, 2021 at 02:12:54PM +0900, Dominique Martinet wrote:
> This is a follow-up on 5f89468e2f06 ("swiotlb: manipulate orig_addr
> when tlb_addr has offset") which fixed unaligned dma mappings,
> making sure the following overflows are caught:
> 
> - offset of the start of the slot within the device bigger than
> requested address' offset, in other words if the base address
> given in swiotlb_tbl_map_single to create the mapping (orig_addr)
> was after the requested address for the sync (tlb_offset) in the
> same block:
> 
>  |------------------------------------------| block
>               <----------------------------> mapped part of the block
>               ^
>               orig_addr
>        ^
>        invalid tlb_addr for sync
> 
> - if the resulting offset was bigger than the allocation size
> this one could happen if the mapping was not until the end. e.g.
> 
>  |------------------------------------------| block
>       <---------------------> mapped part of the block
>       ^                               ^
>       orig_addr                       invalid tlb_addr
> 
> Both should never happen so print a warning and bail out without trying
> to adjust the sizes/offsets: the first one could try to sync from
> orig_addr to whatever is left of the requested size, but the later
> really has nothing to sync there...
> 
> Signed-off-by: Dominique Martinet <dominique.martinet@...ark-techno.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Bumyong Lee <bumyong.lee@...sung.com>
> Cc: Chanho Park <chanho61.park@...sung.com>
> Cc: Christoph Hellwig <hch@....de>
> ---
> 
> Hi Konrad,
> 
> here's the follow up for the swiotlb/caamjr regression I had promissed.

Awesome!
> It doesn't really change anything, and I confirmed I don't hit either of
> the warnings on our board, but it's probably best to have as either
> could really happen.

:nods:

I put it in the devel/for-linus-5.14 and linux-next. Thank you!