* [PATCH] drm/radeon/dpm: Replace one-element array and use struct_size() helper
@ 2020-05-22 1:25 Gustavo A. R. Silva
2020-05-22 7:00 ` Christian König
0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-22 1:25 UTC (permalink / raw)
To: Alex Deucher, Christian König, David Airlie, Daniel Vetter
Cc: amd-gfx, dri-devel, linux-kernel, Gustavo A. R. Silva
The current codebase makes use of one-element arrays in the following
form:
struct something {
int length;
u8 data[1];
};
struct something *instance;
instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
instance->length = size;
memcpy(instance->data, source, size);
but the preferred mechanism to declare variable-length types such as
these ones is a flexible array member[1][2], introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on. So, replace
the one-element array with a flexible-array member.
Also, make use of the new struct_size() helper to properly calculate the
size of struct NISLANDS_SMC_SWSTATE.
This issue was found with the help of Coccinelle and, audited and fixed
_manually_.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
drivers/gpu/drm/amd/amdgpu/si_dpm.h | 2 +-
drivers/gpu/drm/radeon/ni_dpm.c | 7 ++++---
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/si_dpm.h b/drivers/gpu/drm/amd/amdgpu/si_dpm.h
index 6b7d292b919f3..bc0be6818e218 100644
--- a/drivers/gpu/drm/amd/amdgpu/si_dpm.h
+++ b/drivers/gpu/drm/amd/amdgpu/si_dpm.h
@@ -781,7 +781,7 @@ struct NISLANDS_SMC_SWSTATE
uint8_t levelCount;
uint8_t padding2;
uint8_t padding3;
- NISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[1];
+ NISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
};
typedef struct NISLANDS_SMC_SWSTATE NISLANDS_SMC_SWSTATE;
diff --git a/drivers/gpu/drm/radeon/ni_dpm.c b/drivers/gpu/drm/radeon/ni_dpm.c
index b57c37ddd164c..7d81dde509dc9 100644
--- a/drivers/gpu/drm/radeon/ni_dpm.c
+++ b/drivers/gpu/drm/radeon/ni_dpm.c
@@ -2685,11 +2685,12 @@ static int ni_upload_sw_state(struct radeon_device *rdev,
struct rv7xx_power_info *pi = rv770_get_pi(rdev);
u16 address = pi->state_table_start +
offsetof(NISLANDS_SMC_STATETABLE, driverState);
- u16 state_size = sizeof(NISLANDS_SMC_SWSTATE) +
- ((NISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE - 1) * sizeof(NISLANDS_SMC_HW_PERFORMANCE_LEVEL));
+ NISLANDS_SMC_SWSTATE *smc_state;
+ u16 state_size = struct_size(smc_state, levels,
+ NISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE);
int ret;
- NISLANDS_SMC_SWSTATE *smc_state = kzalloc(state_size, GFP_KERNEL);
+ smc_state = kzalloc(state_size, GFP_KERNEL);
if (smc_state == NULL)
return -ENOMEM;
--
2.26.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] drm/radeon/dpm: Replace one-element array and use struct_size() helper
2020-05-22 1:25 [PATCH] drm/radeon/dpm: Replace one-element array and use struct_size() helper Gustavo A. R. Silva
@ 2020-05-22 7:00 ` Christian König
2020-05-22 17:27 ` Gustavo A. R. Silva
0 siblings, 1 reply; 3+ messages in thread
From: Christian König @ 2020-05-22 7:00 UTC (permalink / raw)
To: Gustavo A. R. Silva, Alex Deucher, David Airlie, Daniel Vetter
Cc: amd-gfx, dri-devel, linux-kernel, Gustavo A. R. Silva
Am 22.05.20 um 03:25 schrieb Gustavo A. R. Silva:
> The current codebase makes use of one-element arrays in the following
> form:
>
> struct something {
> int length;
> u8 data[1];
> };
>
> struct something *instance;
>
> instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL);
> instance->length = size;
> memcpy(instance->data, source, size);
>
> but the preferred mechanism to declare variable-length types such as
> these ones is a flexible array member[1][2], introduced in C99:
>
> struct foo {
> int stuff;
> struct boo array[];
> };
>
> By making use of the mechanism above, we will get a compiler warning
> in case the flexible array does not occur last in the structure, which
> will help us prevent some kind of undefined behavior bugs from being
> inadvertently introduced[3] to the codebase from now on. So, replace
> the one-element array with a flexible-array member.
>
> Also, make use of the new struct_size() helper to properly calculate the
> size of struct NISLANDS_SMC_SWSTATE.
>
> This issue was found with the help of Coccinelle and, audited and fixed
> _manually_.
>
> [1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgcc.gnu.org%2Fonlinedocs%2Fgcc%2FZero-Length.html&data=02%7C01%7Cchristian.koenig%40amd.com%7C7dd54e944eff4d17178008d7fdee62d7%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637257072615411745&sdata=fQHnbXZpsgiMjHOr%2By0Uq12jpCYEYbdX5K26iNkwyeM%3D&reserved=0
> [2] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FKSPP%2Flinux%2Fissues%2F21&data=02%7C01%7Cchristian.koenig%40amd.com%7C7dd54e944eff4d17178008d7fdee62d7%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637257072615411745&sdata=gg20YupmqsaW%2Bg3VyJL%2BkjE3kFwnWF1RD1D2QP04OLk%3D&reserved=0
> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> drivers/gpu/drm/amd/amdgpu/si_dpm.h | 2 +-
> drivers/gpu/drm/radeon/ni_dpm.c | 7 ++++---
> 2 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/si_dpm.h b/drivers/gpu/drm/amd/amdgpu/si_dpm.h
> index 6b7d292b919f3..bc0be6818e218 100644
> --- a/drivers/gpu/drm/amd/amdgpu/si_dpm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/si_dpm.h
> @@ -781,7 +781,7 @@ struct NISLANDS_SMC_SWSTATE
> uint8_t levelCount;
> uint8_t padding2;
> uint8_t padding3;
> - NISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[1];
> + NISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[];
> };
>
> typedef struct NISLANDS_SMC_SWSTATE NISLANDS_SMC_SWSTATE;
> diff --git a/drivers/gpu/drm/radeon/ni_dpm.c b/drivers/gpu/drm/radeon/ni_dpm.c
> index b57c37ddd164c..7d81dde509dc9 100644
> --- a/drivers/gpu/drm/radeon/ni_dpm.c
> +++ b/drivers/gpu/drm/radeon/ni_dpm.c
> @@ -2685,11 +2685,12 @@ static int ni_upload_sw_state(struct radeon_device *rdev,
> struct rv7xx_power_info *pi = rv770_get_pi(rdev);
> u16 address = pi->state_table_start +
> offsetof(NISLANDS_SMC_STATETABLE, driverState);
> - u16 state_size = sizeof(NISLANDS_SMC_SWSTATE) +
> - ((NISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE - 1) * sizeof(NISLANDS_SMC_HW_PERFORMANCE_LEVEL));
> + NISLANDS_SMC_SWSTATE *smc_state;
> + u16 state_size = struct_size(smc_state, levels,
> + NISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE);
Probably better to use size_t instead of u16 here. With that fixed feel
free to stick my rb on the patch.
Regards,
Christian.
> int ret;
> - NISLANDS_SMC_SWSTATE *smc_state = kzalloc(state_size, GFP_KERNEL);
>
> + smc_state = kzalloc(state_size, GFP_KERNEL);
> if (smc_state == NULL)
> return -ENOMEM;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] drm/radeon/dpm: Replace one-element array and use struct_size() helper
2020-05-22 7:00 ` Christian König
@ 2020-05-22 17:27 ` Gustavo A. R. Silva
0 siblings, 0 replies; 3+ messages in thread
From: Gustavo A. R. Silva @ 2020-05-22 17:27 UTC (permalink / raw)
To: Christian König
Cc: Alex Deucher, David Airlie, Daniel Vetter, amd-gfx, dri-devel,
linux-kernel, Gustavo A. R. Silva
On Fri, May 22, 2020 at 09:00:09AM +0200, Christian König wrote:
> > +++ b/drivers/gpu/drm/radeon/ni_dpm.c
> > @@ -2685,11 +2685,12 @@ static int ni_upload_sw_state(struct radeon_device *rdev,
> > struct rv7xx_power_info *pi = rv770_get_pi(rdev);
> > u16 address = pi->state_table_start +
> > offsetof(NISLANDS_SMC_STATETABLE, driverState);
> > - u16 state_size = sizeof(NISLANDS_SMC_SWSTATE) +
> > - ((NISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE - 1) * sizeof(NISLANDS_SMC_HW_PERFORMANCE_LEVEL));
> > + NISLANDS_SMC_SWSTATE *smc_state;
> > + u16 state_size = struct_size(smc_state, levels,
> > + NISLANDS_MAX_SMC_PERFORMANCE_LEVELS_PER_SWSTATE);
>
> Probably better to use size_t instead of u16 here. With that fixed feel free
> to stick my rb on the patch.
>
Sure thing. I'll send v2, shortly.
Thanks, Christian.
--
Gustavo
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-05-22 1:25 [PATCH] drm/radeon/dpm: Replace one-element array and use struct_size() helper Gustavo A. R. Silva
2020-05-22 7:00 ` Christian König
2020-05-22 17:27 ` Gustavo A. R. Silva
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