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([2001:67c:2fbc:1:634e:2582:d0aa:ee79]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a9e564942bdsm80136966b.15.2024.10.31.08.19.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 31 Oct 2024 08:19:30 -0700 (PDT) Message-ID: Date: Thu, 31 Oct 2024 16:19:46 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] amdgpu: prevent NULL pointer dereference if ATIF is not supported To: Mario Limonciello Cc: amd-gfx@lists.freedesktop.org, alexander.deucher@amd.com, christian.koenig@amd.com, Xinhui.Pan@amd.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20241029233232.27692-1-antonio@mandelbit.com> <08add1ec-ceae-4f74-83b0-72d0df510950@amd.com> <77ba52f4-dcdc-4fdd-97b7-0163e54e8836@mandelbit.com> <32298ecd-7b7c-4e19-8481-f35249d6e076@amd.com> Content-Language: en-US From: Antonio Quartulli Autocrypt: addr=antonio@mandelbit.com; keydata= xsFNBFN3k+ABEADEvXdJZVUfqxGOKByfkExNpKzFzAwHYjhOb3MTlzSLlVKLRIHxe/Etj13I X6tcViNYiIiJxmeHAH7FUj/yAISW56lynAEt7OdkGpZf3HGXRQz1Xi0PWuUINa4QW+ipaKmv voR4b1wZQ9cZ787KLmu10VF1duHW/IewDx9GUQIzChqQVI3lSHRCo90Z/NQ75ZL/rbR3UHB+ EWLIh8Lz1cdE47VaVyX6f0yr3Itx0ZuyIWPrctlHwV5bUdA4JnyY3QvJh4yJPYh9I69HZWsj qplU2WxEfM6+OlaM9iKOUhVxjpkFXheD57EGdVkuG0YhizVF4p9MKGB42D70pfS3EiYdTaKf WzbiFUunOHLJ4hyAi75d4ugxU02DsUjw/0t0kfHtj2V0x1169Hp/NTW1jkqgPWtIsjn+dkde dG9mXk5QrvbpihgpcmNbtloSdkRZ02lsxkUzpG8U64X8WK6LuRz7BZ7p5t/WzaR/hCdOiQCG RNup2UTNDrZpWxpwadXMnJsyJcVX4BAKaWGsm5IQyXXBUdguHVa7To/JIBlhjlKackKWoBnI Ojl8VQhVLcD551iJ61w4aQH6bHxdTjz65MT2OrW/mFZbtIwWSeif6axrYpVCyERIDEKrX5AV rOmGEaUGsCd16FueoaM2Hf96BH3SI3/q2w+g058RedLOZVZtyQARAQABzSlBbnRvbmlvIFF1 YXJ0dWxsaSA8YW50b25pb0BtYW5kZWxiaXQuY29tPsLBrQQTAQgAVwIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUJFZDZMhYhBMq9oSggF8JnIZiFx0jwzLaPWdFMBQJhFSq4GBhoa3Bz Oi8va2V5cy5vcGVucGdwLm9yZwAKCRBI8My2j1nRTC6+EACi9cdzbzfIaLxGfn/anoQyiK8r FMgjYmWMSMukJMe0OA+v2+/VTX1Zy8fRwhjniFfiypMjtm08spZpLGZpzTQJ2i07jsAZ+0Kv ybRYBVovJQJeUmlkusY3H4dgodrK8RJ5XK0ukabQlRCe2gbMja3ec/p1sk26z25O/UclB2ti YAKnd/KtD9hoJZsq+sZFvPAhPEeMAxLdhRZRNGib82lU0iiQO+Bbox2+Xnh1+zQypxF6/q7n y5KH/Oa3ruCxo57sc+NDkFC2Q+N4IuMbvtJSpL1j6jRc66K9nwZPO4coffgacjwaD4jX2kAp saRdxTTr8npc1MkZ4N1Z+vJu6SQWVqKqQ6as03pB/FwLZIiU5Mut5RlDAcqXxFHsium+PKl3 UDL1CowLL1/2Sl4NVDJAXSVv7BY51j5HiMuSLnI/+99OeLwoD5j4dnxyUXcTu0h3D8VRlYvz iqg+XY2sFugOouX5UaM00eR3Iw0xzi8SiWYXl2pfeNOwCsl4fy6RmZsoAc/SoU6/mvk82OgN ABHQRWuMOeJabpNyEzA6JISgeIrYWXnn1/KByd+QUIpLJOehSd0o2SSLTHyW4TOq0pJJrz03 oRIe7kuJi8K2igJrfgWxN45ctdxTaNW1S6X1P5AKTs9DlP81ZiUYV9QkZkSS7gxpwvP7CCKF n11s24uF1c7ATQRmaEkXAQgA4BaIiPURiRuKTFdJI/cBrOQj5j8gLN0UOaJdetid/+ZgTM5E HQq+o1FA50vKNsso9DBKNgS3W6rApoPUtEtsDsWmS0BKEMrjIiWOTGG8Mjyx6Z9DlYT/UmP8 j9BT7hVeGR3pS++nJC38uJa/IB+8TE8S+GIyeyDbORBsFD8zg2ztyTTNDgFMBXNb8aqhPbPT eaCnUWHGR/Mcwo9DoiYSm5jlxlNDCsFSBaJ/ofMK1AkvsilrZ8WcNogdB6IkbRFeX+D3HdiX BYazE4WulZayHoYjQyjZbaeSKcQi2zjz7A0MEIxwyU5oxinIAjt9PnOIO4bYIEDTrRlPuqp2 XptpdQARAQABwsF8BBgBCAAmFiEEyr2hKCAXwmchmIXHSPDMto9Z0UwFAmZoSRcCGwwFCQHh M4AACgkQSPDMto9Z0UxtFQ//S3kWuMXwpjq4JThPHTb01goM33MmvQJXBIaw18LxZaicqzrp ATWl3rEFWgHO7kicVFZrZ53p3q8HDYFokcLRoyDeLDAFsSA+fgnHz1B9zMUwm8Wb4w1zYMsO uo3NpBKoHNDlK9SPGHyVD6KoCGLQw+/h7ZhtcPRE7I74hNGBBVkFVeg+bggkZhaCZWbE/fih RCEEzuKl8JVtw4VTk4+F33+OfUEIfOKv7+LR9jZn9p7ExgfBdQyFr+K2+wEcZwgRgqTs8v0U R+zCVur69agK1RNRzQCMOAHvoBxRXHEm3HGnK8RL1oXFYPtBz52cYmd/FUkjTNs3Zvft9fXf wF/bs24qmiS/SwGc0S2wPtNjiAHPhCG9E1IGWLQTlsZRuQzfWuHgjPbVCTRwLBH0P+/BBWyA +8aKhGqG8Va0uwS3/EqiU6ZRYD+M/SnzCdD7eNjpr8Mn6jkudUXMWpsrd9KiMpt+vdtjfeJl NKMNf0DgFyiFHKqGek1jIcvfqBo6c2c5z65cUJ2hCQjnfWFePMixWzY6V9G5+4OtbAC/56ba 45MGdFf2cXH2Q9I7jZOQUrnkOvkQN4E7e/fet5yxy4HxVU3nG+HQZXntCt772wmsSrsSz1br T1r4zTJElYkSMWcxr+OwZn5DIsPlBMvpIa5n2AojdbVJ8Vk7NXuEezE9Nno= Organization: Mandelbit SRL In-Reply-To: <32298ecd-7b7c-4e19-8481-f35249d6e076@amd.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 31/10/2024 15:41, Mario Limonciello wrote: > On 10/30/2024 16:06, Antonio Quartulli wrote: >> Hi Mario, >> >> On 30/10/2024 02:41, Mario Limonciello wrote: >>> On 10/29/2024 18:32, Antonio Quartulli wrote: >>>> acpi_evaluate_object() may return AE_NOT_FOUND (failure), which >>>> would result in dereferencing buffer.pointer (obj) while being NULL. >>>> >>>> Bail out also when status is AE_NOT_FOUND with a proper error message. >>>> >>>> This fixes 1 FORWARD_NULL issue reported by Coverity >>>> Report: CID 1600951:  Null pointer dereferences  (FORWARD_NULL) >>>> >>>> Signed-off-by: Antonio Quartulli >>> >>> I'm not really sure how realistic this failure is.  Can you share the >>> full call trace that Coverity identified? >> >> I just checked Coverity Scan and it only says: >> >>      5. Condition status, taking true branch. >>      6. Condition status != 5U /* (acpi_status)(5 | 0) */, taking >> false branch. >> >> The above points are related to: >> >>      if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) >> >> It doesn't show how acpi_evaluate_object() is expected to return >> AE_NOT_FOUND. >> >> This said, if you think this case is unrealistic, why do you check for >> "status != AE_NOT_FOUND" at all? >> >> At this point maybe it would make more sense to simply drop this check >> and always bail out with the current error message. >> >> Basically a patch with the following only: >> >> -       /* Fail if calling the method fails and ATIF is supported */ >> -       if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) { >> +       /* Fail if calling the method fails */ >> +       if (ACPI_FAILURE(status)) { >> >> This way we don't make a fuzz for a possibly unrealistic case, while >> still protecting against bugs and null-dereferences. > > Yeah I think that's a good idea.  Can you respin it as a v2? Will do! Thanks for your feedback, Mario. Regards, > >> >> >> Regards, >> >>> >>> amdgpu_atif_pci_probe_handle() will check whether the handle is >>> available in the first place.  We'll never this this far if that failed. >>> >>> Because of that I don't follow how this could return AE_NOT_FOUND. >>>> --- >>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 11 +++++++---- >>>>   1 file changed, 7 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/ >>>> drm/amd/amdgpu/amdgpu_acpi.c >>>> index cce85389427f..f10c3261a4ab 100644 >>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c >>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c >>>> @@ -172,10 +172,13 @@ static union acpi_object >>>> *amdgpu_atif_call(struct amdgpu_atif *atif, >>>>                         &buffer); >>>>       obj = (union acpi_object *)buffer.pointer; >>>> -    /* Fail if calling the method fails and ATIF is supported */ >>>> -    if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) { >>>> -        DRM_DEBUG_DRIVER("failed to evaluate ATIF got %s\n", >>>> -                 acpi_format_exception(status)); >>>> +    /* Fail if calling the method fails */ >>>> +    if (ACPI_FAILURE(status)) { >>>> +        if (status != AE_NOT_FOUND) >>>> +            DRM_DEBUG_DRIVER("failed to evaluate ATIF got %s\n", >>>> +                     acpi_format_exception(status)); >>>> +        else >>>> +            DRM_DEBUG_DRIVER("ATIF not supported\n"); >>>>           kfree(obj); >>>>           return NULL; >>>>       } >>> >> > -- Antonio Quartulli CEO and Co-Founder Mandelbit Srl https://www.mandelbit.com