linux-kernel - Re: [PATCH 1/8] KVM: SEV-ES: fix length of string I/O

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Mon, 25 Oct 2021 10:59:04 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Marc Orr <marcorr@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        fwilhelm@...gle.com, seanjc@...gle.com, oupton@...gle.com,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/8] KVM: SEV-ES: fix length of string I/O

On 25/10/21 03:31, Marc Orr wrote:
> I could be missing something, but I'm pretty sure that this is wrong.
> The GHCB spec says that `exit_info_2` is the `rep` count. Not the
> string length.
> 
> For example, given a `rep outsw` instruction, with `ECX` set to `8`,
> the rep count written into `SW_EXITINFO2` should be eight x86 words
> (i.e., 16 bytes) and the IO size should be one x86 word (i.e., 2
> bytes). In other words, the code was correct before this patch. This
> patch is incorrectly dividing the rep count by the IO size, causing
> the string IO to be truncated.

Then what's wrong is _also_ the call to setup_vmgexit_scratch, because 
that one definitely expects bytes:

                 scratch_va = kzalloc(len, GFP_KERNEL_ACCOUNT);

Paolo