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Date:   Thu, 1 Dec 2022 10:55:27 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Roberto Sassu <roberto.sassu@huaweicloud.com>
Cc:     zohar@linux.ibm.com, dmitry.kasatkin@gmail.com,
        paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com,
        linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Roberto Sassu <roberto.sassu@huawei.com>,
        stable@vger.kernel.org
Subject: Re: [PATCH v2 2/2] ima: Alloc ima_max_digest_data in xattr_verify()
 if CONFIG_VMAP_STACK=y
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References: <20221201100625.916781-1-roberto.sassu@huaweicloud.com>
 <20221201100625.916781-3-roberto.sassu@huaweicloud.com>
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On Thu, Dec 01, 2022 at 11:06:25AM +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
> 
> Similarly to evm_verify_hmac(), which allocates an evm_digest structure to
> satisfy the linear mapping requirement if CONFIG_VMAP_STACK is enabled, do
> the same in xattr_verify(). Allocate an ima_max_digest_data structure and
> use that instead of the in-stack counterpart.
> 
> Cc: stable@vger.kernel.org # 4.9.x
> Fixes: ba14a194a434 ("fork: Add generic vmalloced stack support")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>

Likewise, what is the actual problem here?  Where specifically is a scatterlist
being used to represent an on-stack buffer?

- Eric