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From: "Christian König" <christian.koenig@amd.com>
To: Tianlin Li <tli@digitalocean.com>,
	kernel-hardening@lists.openwall.com, keescook@chromium.org
Cc: Alex Deucher <alexander.deucher@amd.com>,
	David1.Zhou@amd.com, David Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] drm/radeon: have the callers of set_memory_*() check the return value
Date: Wed, 8 Jan 2020 13:56:47 +0100
Message-ID: <b5984995-7276-97d3-a604-ddacfb89bd89@amd.com> (raw)
In-Reply-To: <20200107192555.20606-1-tli@digitalocean.com>

Am 07.01.20 um 20:25 schrieb Tianlin Li:
> Right now several architectures allow their set_memory_*() family of
> functions to fail, but callers may not be checking the return values.
> If set_memory_*() returns with an error, call-site assumptions may be
> infact wrong to assume that it would either succeed or not succeed at
> all. Ideally, the failure of set_memory_*() should be passed up the
> call stack, and callers should examine the failure and deal with it.
>
> Need to fix the callers and add the __must_check attribute. They also
> may not provide any level of atomicity, in the sense that the memory
> protections may be left incomplete on failure. This issue likely has a
> few steps on effects architectures:
> 1)Have all callers of set_memory_*() helpers check the return value.
> 2)Add __must_check to all set_memory_*() helpers so that new uses do
> not ignore the return value.
> 3)Add atomicity to the calls so that the memory protections aren't left
> in a partial state.
>
> This series is part of step 1. Make drm/radeon check the return value of
> set_memory_*().

I'm a little hesitate merge that. This hardware is >15 years old and 
nobody of the developers have any system left to test this change on.

Would it be to much of a problem to just add something like: r = 
set_memory_*(); (void)r; /* Intentionally ignored */.

Apart from that certainly a good idea to add __must_check to the functions.

Regards,
Christian.

>
> Tianlin Li (2):
>    drm/radeon: have the callers of set_memory_*() check the return value
>    drm/radeon: change call sites to handle return value properly.
>
>   drivers/gpu/drm/radeon/r100.c        |  3 ++-
>   drivers/gpu/drm/radeon/radeon.h      |  2 +-
>   drivers/gpu/drm/radeon/radeon_gart.c | 22 ++++++++++++++++++----
>   drivers/gpu/drm/radeon/rs400.c       |  3 ++-
>   4 files changed, 23 insertions(+), 7 deletions(-)
>


  parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-07 19:25 Tianlin Li
2020-01-07 19:25 ` [PATCH 1/2] " Tianlin Li
2020-01-07 19:25 ` [PATCH 2/2] drm/radeon: change call sites to handle return value properly Tianlin Li
2020-01-08 12:56 ` Christian König [this message]
2020-01-08 16:04   ` [PATCH 0/2] drm/radeon: have the callers of set_memory_*() check the return value Tianlin Li
2020-01-08 17:39   ` Kees Cook
2020-01-08 17:51     ` Alex Deucher
2020-01-09 10:15       ` Christian König
2020-01-09 10:49         ` Thomas Zimmermann
2020-01-09 20:16           ` Alex Deucher

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