linux-kernel - Re: [PATCH 4.19 1/1] drm/amdkfd: Check for null pointer after calling kmemdup

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Date:   Wed, 4 Jan 2023 09:35:03 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     Christian König <christian.koenig@....com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Dragos-Marian Panait <dragos.panait@...driver.com>,
        Oded Gabbay <oded.gabbay@...il.com>,
        David Zhou <David1.Zhou@....com>,
        amd-gfx@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Jiasheng Jiang <jiasheng@...as.ac.cn>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Alex Deucher <alexander.deucher@....com>
Subject: Re: [PATCH 4.19 1/1] drm/amdkfd: Check for null pointer after calling kmemdup

On Wed, Jan 4, 2023 at 8:23 AM Christian König <christian.koenig@....com> wrote:
>
> Am 04.01.23 um 13:41 schrieb Greg KH:
> > On Tue, Jan 03, 2023 at 08:43:08PM +0200, Dragos-Marian Panait wrote:
> >> From: Jiasheng Jiang <jiasheng@...as.ac.cn>
> >>
> >> [ Upstream commit abfaf0eee97925905e742aa3b0b72e04a918fa9e ]
> >>
> >> As the possible failure of the allocation, kmemdup() may return NULL
> >> pointer.
> >> Therefore, it should be better to check the 'props2' in order to prevent
> >> the dereference of NULL pointer.
> >>
> >> Fixes: 3a87177eb141 ("drm/amdkfd: Add topology support for dGPUs")
> >> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> >> Reviewed-by: Felix Kuehling <Felix.Kuehling@....com>
> >> Signed-off-by: Felix Kuehling <Felix.Kuehling@....com>
> >> Signed-off-by: Alex Deucher <alexander.deucher@....com>
> >> Signed-off-by: Dragos-Marian Panait <dragos.panait@...driver.com>
> >> ---
> >>   drivers/gpu/drm/amd/amdkfd/kfd_crat.c | 3 +++
> >>   1 file changed, 3 insertions(+)
> > For obvious reasons, I can't take a patch for 4.19.y and not newer
> > kernel releases, right?
> >
> > Please provide backports for all kernels if you really need to see this
> > merged.  And note, it's not a real bug at all, and given that a CVE was
> > allocated for it that makes me want to even more reject it to show the
> > whole folly of that mess.
>
> Well as far as I can see this is nonsense to back port.
>
> The code in question is only used only once during driver load and then
> never again, that exactly this allocation fails while tons of other are
> made before and after is extremely unlikely.
>
> It's nice to have it fixed in newer kernels, but not worth a backport
> and certainly not stuff for a CVE.

It's already fixed in Linus' tree:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=abfaf0eee97925905e742aa3b0b72e04a918fa9e

Alex

>
> Regards,
> Christian.
>
>
> >
> > thanks,
> >
> > greg k-h
>