linux-kernel - Re: [PATCH -next v2] iommu/amd: fix a null-ptr-deref in map

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Date:   Tue, 7 May 2019 09:39:01 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Qian Cai <cai@....pw>
Cc:     tmurphy@...sta.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v2] iommu/amd: fix a null-ptr-deref in map_sg()

Hi Qian,

On Mon, May 06, 2019 at 12:44:40PM -0400, Qian Cai wrote:
> The commit 1a1079011da3 ("iommu/amd: Flush not present cache in
> iommu_map_page") added domain_flush_np_cache() in map_sg() which
> triggered a crash below during boot. sg_next() could return NULL if
> sg_is_last() is true, so after for_each_sg(sglist, s, nelems, i), "s"
> could be NULL which ends up deferencing a NULL pointer later here,
> 
> domain_flush_np_cache(domain, s->dma_address, s->dma_length);
> 
> so move domain_flush_np_cache() call inside for_each_sg() to loop over
> each sg element.

Thanks for the fix, but it is too late to merge it into the tree. I am
going to revert commit 1a1079011da3 for now and we can try again in the
next cycle.


Thanks,

	Joerg