From: Shuah Khan <skhan@linuxfoundation.org>
To: Jarkko Sakkinen <jarkko@kernel.org>, Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org, linux-sgx@vger.kernel.org,
Reinette Chatre <reinette.chatre@intel.com>,
Borislav Petkov <bp@alien8.de>,
Tianjia Zhang <tianjia.zhang@linux.alibaba.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-kernel@vger.kernel.org,
Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH v2] selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c
Date: Fri, 23 Jul 2021 13:53:06 -0600 [thread overview]
Message-ID: <be6227d1-728a-c658-f962-380c28afc926@linuxfoundation.org> (raw)
In-Reply-To: <20210705050922.63710-1-jarkko@kernel.org>
On 7/4/21 11:09 PM, Jarkko Sakkinen wrote:
> From: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
>
> Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
> length of Q1 and Q2 is less than 384 bytes, things will go wrong.
>
> E.g. if Q2 is 383 bytes, then
>
> 1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
> 2. The entire sigstruct->q2 is reversed, which results it being
> 256 * Q2, given that the last byte of sigstruct->q2 is added
> to before the bytes given by calc_q1q2().
>
> Either change in key or measurement can trigger the bug. E.g. an unmeasured
> heap could cause a devastating change in Q1 or Q2.
>
> Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
> the caller.
>
> Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")
> Link: https://lore.kernel.org/linux-sgx/20210301051836.30738-1-tianjia.zhang@linux.alibaba.com/
> Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> The original patch did a bad job explaining the code change but it
> turned out making sense. I wrote a new description.
>
> v2:
> - Added a fixes tag.
> tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------
> 1 file changed, 21 insertions(+), 20 deletions(-)
>
> diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c
> index dee7a3d6c5a5..92bbc5a15c39 100644
> --- a/tools/testing/selftests/sgx/sigstruct.c
> +++ b/tools/testing/selftests/sgx/sigstruct.c
> @@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
> return true;
> }
>
> +static void reverse_bytes(void *data, int length)
> +{
> + int i = 0;
> + int j = length - 1;
> + uint8_t temp;
> + uint8_t *ptr = data;
> +
> + while (i < j) {
> + temp = ptr[i];
> + ptr[i] = ptr[j];
> + ptr[j] = temp;
> + i++;
> + j--;
> + }
> +}
I was just about apply this one and noticed this reverse_bytes().
Aren't there byteswap functions you could call instead of writing
your own?
thanks,
-- Shuah
next prev parent reply other threads:[~2021-07-23 19:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-05 5:09 [PATCH v2] selftests/sgx: Fix Q1 and Q2 calculation in sigstruct.c Jarkko Sakkinen
2021-07-05 5:10 ` Jarkko Sakkinen
2021-07-23 19:53 ` Shuah Khan [this message]
2021-07-27 3:12 ` Jarkko Sakkinen
2021-07-29 21:33 ` Shuah Khan
2021-07-30 1:03 ` Jarkko Sakkinen
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