linux-kernel - Re: [PATCH 04/10] swiotlb: Use free_decrypted

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Message-ID: <20231018044333.GA15759@lst.de>
Date:   Wed, 18 Oct 2023 06:43:33 +0200
From:   Christoph Hellwig <hch@....de>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc:     x86@...nel.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, luto@...nel.org,
        peterz@...radead.org, kirill.shutemov@...ux.intel.com,
        elena.reshetova@...el.com, isaku.yamahata@...el.com,
        seanjc@...gle.com, Michael Kelley <mikelley@...rosoft.com>,
        thomas.lendacky@....com, decui@...rosoft.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev
Subject: Re: [PATCH 04/10] swiotlb: Use free_decrypted_pages()

On Tue, Oct 17, 2023 at 01:24:59PM -0700, Rick Edgecombe wrote:
> On TDX it is possible for the untrusted host to cause
> set_memory_encrypted() or set_memory_decrypted() to fail such that an
> error is returned and the resulting memory is shared. Callers need to take
> care to handle these errors to avoid returning decrypted (shared) memory to
> the page allocator, which could lead to functional or security issues.
> 
> Swiotlb could free decrypted/shared pages if set_memory_decrypted() fails.
> Use the recently added free_decrypted_pages() to avoid this.
> 
> In swiotlb_exit(), check for set_memory_encrypted() errors manually,
> because the pages are not nessarily going to the page allocator.

Whatever recently introduced it didn't make it to my mailbox.  Please
always CC everyone on every patch in a series, everything else is
impossible to review.