linux-kernel - Re: [PATCH][RFC] platform/x86: dell-smbios-wmi: Avoid false-positive memcpy() warning

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Message-ID: <YSZwnXqIaIo+hG37@smile.fi.intel.com>
Date:   Wed, 25 Aug 2021 19:32:29 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Mario Limonciello <mario.limonciello@...l.com>,
        Pali Rohár <pali@...nel.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Dell.Client.Kernel@...l.com,
        platform-driver-x86@...r.kernel.org,
        Andy Lavr <andy.lavr@...il.com>, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][RFC] platform/x86: dell-smbios-wmi: Avoid false-positive
 memcpy() warning

On Wed, Aug 25, 2021 at 09:07:49AM -0700, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memcpy(), memmove(), and memset(), avoid
> intentionally writing across neighboring fields.
> 
> Since all the size checking has already happened, use input.pointer
> (void *) so memcpy() doesn't get confused about how much is being
> written.
> 
> Avoids this false-positive warning when run-time memcpy() strict
> bounds checking is enabled:
> 
> memcpy: detected field-spanning write (size 4096) of single field (size 36)
> WARNING: CPU: 0 PID: 357 at drivers/platform/x86/dell/dell-smbios-wmi.c:74 run_smbios_call+0x110/0x1e0 [dell_smbios]

> Note: is there a missed kfree() in the marked error path?

Seems so.

* Note: The caller should use acpi_os_free to free this
* buffer created via ACPI_ALLOCATE_BUFFER.


-- 
With Best Regards,
Andy Shevchenko