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

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Message-ID: <Y7WRq7MaFaIJ2uGF@kroah.com>
Date:   Wed, 4 Jan 2023 15:48:11 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Alex Deucher <alexdeucher@...il.com>
Cc:     Christian König <christian.koenig@....com>,
        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 04, 2023 at 09:35:03AM -0500, Alex Deucher wrote:
> 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

Yes, that's what the above commit shows...

confused,

greg k-h