From 4541ea81edde6ce9a1d9be082489aca7e8e7e1dc Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Fri, 22 May 2020 12:43:55 -0500 Subject: [PATCH] drm/[radeon|amdgpu]: Replace one-element array and use struct_size() helper 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 SISLANDS_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 Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/amdgpu/si_dpm.c | 5 ++--- drivers/gpu/drm/amd/amdgpu/sislands_smc.h | 2 +- drivers/gpu/drm/radeon/si_dpm.c | 5 ++--- 3 files changed, 5 insertions(+), 7 deletions(-) diff --git a/drivers/gpu/drm/amd/amdgpu/si_dpm.c b/drivers/gpu/drm/amd/amdgpu/si_dpm.c index c00ba4b23c9a..0fc56c5bac08 100644 --- a/drivers/gpu/drm/amd/amdgpu/si_dpm.c +++ b/drivers/gpu/drm/amd/amdgpu/si_dpm.c @@ -5715,10 +5715,9 @@ static int si_upload_sw_state(struct amdgpu_device *adev, int ret; u32 address = si_pi->state_table_start + offsetof(SISLANDS_SMC_STATETABLE, driverState); - u32 state_size = sizeof(SISLANDS_SMC_SWSTATE) + - ((new_state->performance_level_count - 1) * - sizeof(SISLANDS_SMC_HW_PERFORMANCE_LEVEL)); SISLANDS_SMC_SWSTATE *smc_state = &si_pi->smc_statetable.driverState; + size_t state_size = struct_size(smc_state, levels, + new_state->performance_level_count); memset(smc_state, 0, state_size); diff --git a/drivers/gpu/drm/amd/amdgpu/sislands_smc.h b/drivers/gpu/drm/amd/amdgpu/sislands_smc.h index d2930eceaf3c..a089dbf8f7a9 100644 --- a/drivers/gpu/drm/amd/amdgpu/sislands_smc.h +++ b/drivers/gpu/drm/amd/amdgpu/sislands_smc.h @@ -186,7 +186,7 @@ struct SISLANDS_SMC_SWSTATE uint8_t levelCount; uint8_t padding2; uint8_t padding3; - SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[1]; + SISLANDS_SMC_HW_PERFORMANCE_LEVEL levels[]; }; typedef struct SISLANDS_SMC_SWSTATE SISLANDS_SMC_SWSTATE; diff --git a/drivers/gpu/drm/radeon/si_dpm.c b/drivers/gpu/drm/radeon/si_dpm.c index a167e1c36d24..bab01ca864c6 100644 --- a/drivers/gpu/drm/radeon/si_dpm.c +++ b/drivers/gpu/drm/radeon/si_dpm.c @@ -5253,10 +5253,9 @@ static int si_upload_sw_state(struct radeon_device *rdev, int ret; u32 address = si_pi->state_table_start + offsetof(SISLANDS_SMC_STATETABLE, driverState); - u32 state_size = sizeof(SISLANDS_SMC_SWSTATE) + - ((new_state->performance_level_count - 1) * - sizeof(SISLANDS_SMC_HW_PERFORMANCE_LEVEL)); SISLANDS_SMC_SWSTATE *smc_state = &si_pi->smc_statetable.driverState; + size_t state_size = struct_size(smc_state, levels, + new_state->performance_level_count); memset(smc_state, 0, state_size); -- 2.25.1