2022-11-02 15:44:59

by Nathan Chancellor

Subject: [PATCH 1/2] drm/amdgpu: Fix type of second parameter in trans_msg() callback

With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
indirect call targets are validated against the expected function
pointer prototype to make sure the call target is valid to help mitigate
ROP attacks. If they are not identical, there is a failure at run time,
which manifests as either a kernel panic or thread getting killed. A
proposed warning in clang aims to catch these at compile time, which
reveals:

drivers/gpu/drm/amd/amdgpu/mxgpu_ai.c:412:15: error: incompatible function pointer types initializing 'void (*)(struct amdgpu_device *, u32, u32, u32, u32)' (aka 'void (*)(struct amdgpu_device *, unsigned int, unsigned int, unsigned int, unsigned int)') with an expression of type 'void (struct amdgpu_device *, enum idh_request, u32, u32, u32)' (aka 'void (struct amdgpu_device *, enum idh_request, unsigned int, unsigned int, unsigned int)') [-Werror,-Wincompatible-function-pointer-types-strict]
.trans_msg = xgpu_ai_mailbox_trans_msg,
^~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

drivers/gpu/drm/amd/amdgpu/mxgpu_nv.c:435:15: error: incompatible function pointer types initializing 'void (*)(struct amdgpu_device *, u32, u32, u32, u32)' (aka 'void (*)(struct amdgpu_device *, unsigned int, unsigned int, unsigned int, unsigned int)') with an expression of type 'void (struct amdgpu_device *, enum idh_request, u32, u32, u32)' (aka 'void (struct amdgpu_device *, enum idh_request, unsigned int, unsigned int, unsigned int)') [-Werror,-Wincompatible-function-pointer-types-strict]
.trans_msg = xgpu_nv_mailbox_trans_msg,
^~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

The type of the second parameter in the prototype should be 'enum
idh_request' instead of 'u32'. Update it to clear up the warnings.

Link: https://github.com/ClangBuiltLinux/linux/issues/1750
Reported-by: Sami Tolvanen <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
index d94c31e68a14..bc4f079fd48c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_virt.h
@@ -74,6 +74,8 @@ struct amdgpu_vf_error_buffer {
uint64_t data[AMDGPU_VF_ERROR_ENTRY_SIZE];
};

+enum idh_request;
+
/**
* struct amdgpu_virt_ops - amdgpu device virt operations
*/
@@ -83,7 +85,8 @@ struct amdgpu_virt_ops {
int (*req_init_data)(struct amdgpu_device *adev);
int (*reset_gpu)(struct amdgpu_device *adev);
int (*wait_reset)(struct amdgpu_device *adev);
- void (*trans_msg)(struct amdgpu_device *adev, u32 req, u32 data1, u32 data2, u32 data3);
+ void (*trans_msg)(struct amdgpu_device *adev, enum idh_request req,
+ u32 data1, u32 data2, u32 data3);
};

/*

base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780
--
2.38.1

2022-11-02 15:48:42

by Kees Cook

Subject: Re: [PATCH 1/2] drm/amdgpu: Fix type of second parameter in trans_msg() callback

On Wed, Nov 02, 2022 at 08:25:39AM -0700, Nathan Chancellor wrote:
> With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
> indirect call targets are validated against the expected function
> pointer prototype to make sure the call target is valid to help mitigate
> ROP attacks. If they are not identical, there is a failure at run time,
> which manifests as either a kernel panic or thread getting killed. A
> proposed warning in clang aims to catch these at compile time, which
> reveals:
>
> drivers/gpu/drm/amd/amdgpu/mxgpu_ai.c:412:15: error: incompatible function pointer types initializing 'void (*)(struct amdgpu_device *, u32, u32, u32, u32)' (aka 'void (*)(struct amdgpu_device *, unsigned int, unsigned int, unsigned int, unsigned int)') with an expression of type 'void (struct amdgpu_device *, enum idh_request, u32, u32, u32)' (aka 'void (struct amdgpu_device *, enum idh_request, unsigned int, unsigned int, unsigned int)') [-Werror,-Wincompatible-function-pointer-types-strict]
> .trans_msg = xgpu_ai_mailbox_trans_msg,
> ^~~~~~~~~~~~~~~~~~~~~~~~~
> 1 error generated.
>
> drivers/gpu/drm/amd/amdgpu/mxgpu_nv.c:435:15: error: incompatible function pointer types initializing 'void (*)(struct amdgpu_device *, u32, u32, u32, u32)' (aka 'void (*)(struct amdgpu_device *, unsigned int, unsigned int, unsigned int, unsigned int)') with an expression of type 'void (struct amdgpu_device *, enum idh_request, u32, u32, u32)' (aka 'void (struct amdgpu_device *, enum idh_request, unsigned int, unsigned int, unsigned int)') [-Werror,-Wincompatible-function-pointer-types-strict]
> .trans_msg = xgpu_nv_mailbox_trans_msg,
> ^~~~~~~~~~~~~~~~~~~~~~~~~
> 1 error generated.
>
> The type of the second parameter in the prototype should be 'enum
> idh_request' instead of 'u32'. Update it to clear up the warnings.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1750
> Reported-by: Sami Tolvanen <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>

Reviewed-by: Kees Cook <[email protected]>

--
Kees Cook