| Message ID | 20200522012547.GA6783@embeddedor (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/radeon/dpm: Replace one-element array and use struct_size() helper | expand |
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; >
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
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;
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(-)