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Subject: Re: [PATCH v2] drm/radeon: have the callers of set_memory_*() check the return value To: Tianlin Li , kernel-hardening@lists.openwall.com Cc: keescook@chromium.org, Alex Deucher , David1.Zhou@amd.com, David Airlie , Daniel Vetter , amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20200203161827.768-1-tli@digitalocean.com> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <6e5a18f6-b7f6-c401-c845-fe24b183f348@amd.com> Date: Mon, 3 Feb 2020 18:16:33 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 In-Reply-To: <20200203161827.768-1-tli@digitalocean.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-ClientProxiedBy: AM0PR05CA0086.eurprd05.prod.outlook.com (2603:10a6:208:136::26) To DM5PR12MB1705.namprd12.prod.outlook.com (2603:10b6:3:10c::22) MIME-Version: 1.0 X-Originating-IP: [2a02:908:1252:fb60:be8a:bd56:1f94:86e7] X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: 6b603d2b-343a-4008-4cbe-08d7a8ccd4ba X-MS-TrafficTypeDiagnostic: DM5PR12MB1209:|DM5PR12MB1209: X-MS-Exchange-Transport-Forked: True X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; 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Which architectures are that? Cause the RS400/480, RS690 and RS740 which are affected by this are integrated in the south-bridge. > 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 Reviewed-by: Christian König > --- > 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 > --- > 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,