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Subject: Re: [PATCH v2] platform/x86/amd/pmf: Use memdup_user()
From: Thorsten Blum <thorsten.blum@toblux.com>
In-Reply-To: <4c2c8a76-17c7-4dbb-96ff-8488c8e953ff@moroto.mountain>
Date: Thu, 30 May 2024 16:15:51 +0200
Cc: markus.elfring@web.de,
 Shyam-sundar.S-k@amd.com,
 hdegoede@redhat.com,
 ilpo.jarvinen@linux.intel.com,
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 platform-driver-x86@vger.kernel.org
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 <4c2c8a76-17c7-4dbb-96ff-8488c8e953ff@moroto.mountain>
To: Dan Carpenter <dan.carpenter@linaro.org>

Hi Dan,

On 27. May 2024, at 12:38, Dan Carpenter <dan.carpenter@linaro.org> wrote:
> Also this check isn't great:
> 
> if (dev->policy_sz < header->length + 512)
> 
> header->length is a u32 that comes from the user, so the addition can
> overflow.  I can't immediately see how to exploit this though since we
> don't seem to use header->length after this (by itself).

How about

	if (header->length > U32_MAX - 512 || dev->policy_sz < header->length + 512)
		return -EINVAL;

to prevent a possible overflow?

header->length is used in the next line

	dev->policy_sz = header->length + 512;

and if the addition overflows, we end up setting dev->policy_sz to an 
invalid value.

Thanks,
Thorsten