Re: [PATCH 5.4 40/49] drm/i915/gem: Serialise debugfs i915_gem_objects with ctx->mutex

Greg Kroah-Hartman
2020-10-31T11:50:02Z

On Sat, Oct 31, 2020 at 12:35:36PM +0100, Greg Kroah-Hartman wrote:
> From: Chris Wilson <chris@chris-wilson.co.uk>
>
> commit 4fe9af8e881d946bf60790eeb37a7c4f96e28382 upstream.
>
> Since the debugfs may peek into the GEM contexts as the corresponding
> client/fd is being closed, we may try and follow a dangling pointer.
> However, the context closure itself is serialised with the ctx->mutex,
> so if we hold that mutex as we inspect the state coupled in the context,
> we know the pointers within the context are stable and will remain valid
> as we inspect their tables.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: CQ Tang <cq.tang@intel.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: stable@vger.kernel.org
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Link: https://patchwork.freedesktop.org/patch/msgid/20200723172119.17649-3-chris@chris-wilson.co.uk
> (cherry picked from commit 102f5aa491f262c818e607fc4fee08a724a76c69)
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> drivers/gpu/drm/i915/i915_debugfs.c | 2 ++
> 1 file changed, 2 insertions(+)

Oops, nope, this breaks the build here, now dropping it...

greg k-h