On 03.08.2016 11:09, Dan Carpenter wrote:
Hello Nicolai Hähnle,
The patch 324c614a819a: "drm/amdgpu/gfx7: set
USER_SHADER_ARRAY_CONFIG based on disable_cu parameter" from Jun 17,
2016, leads to the following static checker warning:
drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c:5057 gfx_v7_0_get_cu_info()
error: buffer overflow 'cu_info->bitmap' 4 <= 4
drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c
5035 static void gfx_v7_0_get_cu_info(struct amdgpu_device *adev)
5036 {
5037 int i, j, k, counter, active_cu_number = 0;
5038 u32 mask, bitmap, ao_bitmap, ao_cu_mask = 0;
5039 struct amdgpu_cu_info *cu_info = &adev->gfx.cu_info;
5040 unsigned disable_masks[4 * 2];
5041
5042 memset(cu_info, 0, sizeof(*cu_info));
5043
5044 amdgpu_gfx_parse_disable_cu(disable_masks, 4, 2);
5045
5046 mutex_lock(&adev->grbm_idx_mutex);
5047 for (i = 0; i < adev->gfx.config.max_shader_engines; i++) {
5048 for (j = 0; j < adev->gfx.config.max_sh_per_se; j++) {
5049 mask = 1;
5050 ao_bitmap = 0;
5051 counter = 0;
5052 gfx_v7_0_select_se_sh(adev, i, j, 0xffffffff);
5053 if (i < 4 && j < 2)
^^^^^
Is it really possible for i to be >= 4?
No, because for that to happen we would have to add support for hardware
with > 4 shader engines. What's the idiomatic way to express this kind
of assumption in the kernel? BUG_ON(adev->gfx.config.max_shader_engines
> 4)? Some other form of assert?
Nicolai
5054 gfx_v7_0_set_user_cu_inactive_bitmap(
5055 adev, disable_masks[i * 2 + j]);
5056 bitmap = gfx_v7_0_get_cu_active_bitmap(adev);
5057 cu_info->bitmap[i][j] = bitmap;
^^^^^^^^^^^^^^^^^^^^^
Because if so, then we are screwed here.
5058
5059 for (k = 0; k < 16; k ++) {
5060 if (bitmap & mask) {
5061 if (counter < 2)
5062 ao_bitmap |= mask;
5063 counter ++;
5064 }
5065 mask <<= 1;
5066 }
5067 active_cu_number += counter;
5068 ao_cu_mask |= (ao_bitmap << (i * 16 + j * 8));
5069 }
5070 }
5071 gfx_v7_0_select_se_sh(adev, 0xffffffff, 0xffffffff, 0xffffffff);
5072 mutex_unlock(&adev->grbm_idx_mutex);
5073
5074 cu_info->number = active_cu_number;
5075 cu_info->ao_cu_mask = ao_cu_mask;
5076 }
regards,
dan carpenter
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