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Message-Id: <D9D0C673-E931-46D2-A0F2-48F46901EA20@digitalocean.com>
Date: Mon, 3 Feb 2020 14:44:56 -0600
From: Tianlin Li <tli@...italocean.com>
To: Christian König <christian.koenig@....com>
Cc: kernel-hardening@...ts.openwall.com,
Kees Cook <keescook@...omium.org>,
Alex Deucher <alexander.deucher@....com>,
David1.Zhou@....com,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
amd-gfx@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/radeon: have the callers of set_memory_*() check
the return value
> On Feb 3, 2020, at 11:16 AM, Christian König <christian.koenig@....com> wrote:
>
> Am 03.02.20 um 17:18 schrieb Tianlin Li:
>> Right now several architectures allow their set_memory_*() family of
>> functions to fail,
>
> Oh, that is a detail I previously didn't recognized. Which architectures are that?
>
> Cause the RS400/480, RS690 and RS740 which are affected by this are integrated in the south-bridge.
At least x86 is.
Some details: https://lore.kernel.org/netdev/20180628213459.28631-4-daniel@iogearbox.net/ <https://lore.kernel.org/netdev/20180628213459.28631-4-daniel@iogearbox.net/>
>> 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_*().
>>
>> Signed-off-by: Tianlin Li <tli@...italocean.com>
>
> Reviewed-by: Christian König <christian.koenig@....com <mailto:christian.koenig@....com>>
>
>> ---
>> v2:
>> The hardware is too old to be tested on and the code cannot be simply
>> removed from the kernel, so this is the solution for the short term.
>> - Just print an error when something goes wrong
>> - Remove patch 2.
>> v1:
>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flkml%2F20200107192555.20606-1-tli%40digitalocean.com%2F&data=02%7C01%7Cchristian.koenig%40amd.com%7Cba2176d2ca834214e6b108d7a8c4bb1d%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637163435227030235&sdata=mDhUEi3vmxahjsdrZOr83OEIWNBHefO8lkXST%2FW32CE%3D&reserved=0 <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flkml%2F20200107192555.20606-1-tli%40digitalocean.com%2F&data=02%7C01%7Cchristian.koenig%40amd.com%7Cba2176d2ca834214e6b108d7a8c4bb1d%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637163435227030235&sdata=mDhUEi3vmxahjsdrZOr83OEIWNBHefO8lkXST%2FW32CE%3D&reserved=0>
>> ---
>> drivers/gpu/drm/radeon/radeon_gart.c | 10 ++++++----
>> 1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/radeon/radeon_gart.c b/drivers/gpu/drm/radeon/radeon_gart.c
>> index f178ba321715..a2cc864aa08d 100644
>> --- a/drivers/gpu/drm/radeon/radeon_gart.c
>> +++ b/drivers/gpu/drm/radeon/radeon_gart.c
>> @@ -80,8 +80,9 @@ int radeon_gart_table_ram_alloc(struct radeon_device *rdev)
>> #ifdef CONFIG_X86
>> if (rdev->family == CHIP_RS400 || rdev->family == CHIP_RS480 ||
>> rdev->family == CHIP_RS690 || rdev->family == CHIP_RS740) {
>> - set_memory_uc((unsigned long)ptr,
>> - rdev->gart.table_size >> PAGE_SHIFT);
>> + if (set_memory_uc((unsigned long)ptr,
>> + rdev->gart.table_size >> PAGE_SHIFT))
>> + DRM_ERROR("set_memory_uc failed.\n");
>> }
>> #endif
>> rdev->gart.ptr = ptr;
>> @@ -106,8 +107,9 @@ void radeon_gart_table_ram_free(struct radeon_device *rdev)
>> #ifdef CONFIG_X86
>> if (rdev->family == CHIP_RS400 || rdev->family == CHIP_RS480 ||
>> rdev->family == CHIP_RS690 || rdev->family == CHIP_RS740) {
>> - set_memory_wb((unsigned long)rdev->gart.ptr,
>> - rdev->gart.table_size >> PAGE_SHIFT);
>> + if (set_memory_wb((unsigned long)rdev->gart.ptr,
>> + rdev->gart.table_size >> PAGE_SHIFT))
>> + DRM_ERROR("set_memory_wb failed.\n");
>> }
>> #endif
>> pci_free_consistent(rdev->pdev, rdev->gart.table_size,
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