On Wed, Jul 29, 2020 at 10:11 AM Christian König
<ckoenig.leichtzumerken@xxxxxxxxx> wrote:
>
> Am 28.07.20 um 21:29 schrieb Peilin Ye:
> > Compiler leaves a 4-byte hole near the end of `dev_info`, causing
> > amdgpu_info_ioctl() to copy uninitialized kernel stack memory to userspace
> > when `size` is greater than 356.
> >
> > In 2015 we tried to fix this issue by doing `= {};` on `dev_info`, which
> > unfortunately does not initialize that 4-byte hole. Fix it by using
> > memset() instead.
> >
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: c193fa91b918 ("drm/amdgpu: information leak in amdgpu_info_ioctl()")
> > Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
> > Suggested-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
>
> Reviewed-by: Christian König <christian.koenig@xxxxxxx>
>
> I can't count how many of those we have fixed over the years.
>
> At some point we should probably document that using "= {}" or "= { 0 }"
> in the kernel is a really bad idea and should be avoided.
I think the rule is also "don't create uapi structs with holes in
them", but we've also fumbled that one quite a few times :-/
-Daniel
>
> Thanks,
> Christian.
>
> > ---
> > $ pahole -C "drm_amdgpu_info_device" drivers/gpu/drm/amd/amdgpu/amdgpu_kms.o
> > struct drm_amdgpu_info_device {
> > __u32 device_id; /* 0 4 */
> > __u32 chip_rev; /* 4 4 */
> > __u32 external_rev; /* 8 4 */
> > __u32 pci_rev; /* 12 4 */
> > __u32 family; /* 16 4 */
> > __u32 num_shader_engines; /* 20 4 */
> > __u32 num_shader_arrays_per_engine; /* 24 4 */
> > __u32 gpu_counter_freq; /* 28 4 */
> > __u64 max_engine_clock; /* 32 8 */
> > __u64 max_memory_clock; /* 40 8 */
> > __u32 cu_active_number; /* 48 4 */
> > __u32 cu_ao_mask; /* 52 4 */
> > __u32 cu_bitmap[4][4]; /* 56 64 */
> > /* --- cacheline 1 boundary (64 bytes) was 56 bytes ago --- */
> > __u32 enabled_rb_pipes_mask; /* 120 4 */
> > __u32 num_rb_pipes; /* 124 4 */
> > /* --- cacheline 2 boundary (128 bytes) --- */
> > __u32 num_hw_gfx_contexts; /* 128 4 */
> > __u32 _pad; /* 132 4 */
> > __u64 ids_flags; /* 136 8 */
> > __u64 virtual_address_offset; /* 144 8 */
> > __u64 virtual_address_max; /* 152 8 */
> > __u32 virtual_address_alignment; /* 160 4 */
> > __u32 pte_fragment_size; /* 164 4 */
> > __u32 gart_page_size; /* 168 4 */
> > __u32 ce_ram_size; /* 172 4 */
> > __u32 vram_type; /* 176 4 */
> > __u32 vram_bit_width; /* 180 4 */
> > __u32 vce_harvest_config; /* 184 4 */
> > __u32 gc_double_offchip_lds_buf; /* 188 4 */
> > /* --- cacheline 3 boundary (192 bytes) --- */
> > __u64 prim_buf_gpu_addr; /* 192 8 */
> > __u64 pos_buf_gpu_addr; /* 200 8 */
> > __u64 cntl_sb_buf_gpu_addr; /* 208 8 */
> > __u64 param_buf_gpu_addr; /* 216 8 */
> > __u32 prim_buf_size; /* 224 4 */
> > __u32 pos_buf_size; /* 228 4 */
> > __u32 cntl_sb_buf_size; /* 232 4 */
> > __u32 param_buf_size; /* 236 4 */
> > __u32 wave_front_size; /* 240 4 */
> > __u32 num_shader_visible_vgprs; /* 244 4 */
> > __u32 num_cu_per_sh; /* 248 4 */
> > __u32 num_tcc_blocks; /* 252 4 */
> > /* --- cacheline 4 boundary (256 bytes) --- */
> > __u32 gs_vgt_table_depth; /* 256 4 */
> > __u32 gs_prim_buffer_depth; /* 260 4 */
> > __u32 max_gs_waves_per_vgt; /* 264 4 */
> > __u32 _pad1; /* 268 4 */
> > __u32 cu_ao_bitmap[4][4]; /* 272 64 */
> > /* --- cacheline 5 boundary (320 bytes) was 16 bytes ago --- */
> > __u64 high_va_offset; /* 336 8 */
> > __u64 high_va_max; /* 344 8 */
> > __u32 pa_sc_tile_steering_override; /* 352 4 */
> >
> > /* XXX 4 bytes hole, try to pack */
> >
> > __u64 tcc_disabled_mask; /* 360 8 */
> >
> > /* size: 368, cachelines: 6, members: 49 */
> > /* sum members: 364, holes: 1, sum holes: 4 */
> > /* last cacheline: 48 bytes */
> > };
> >
> > drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> > index a8c47aecd342..0047da06041f 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_kms.c
> > @@ -707,9 +707,10 @@ static int amdgpu_info_ioctl(struct drm_device *dev, void *data, struct drm_file
> > return n ? -EFAULT : 0;
> > }
> > case AMDGPU_INFO_DEV_INFO: {
> > - struct drm_amdgpu_info_device dev_info = {};
> > + struct drm_amdgpu_info_device dev_info;
> > uint64_t vm_size;
> >
> > + memset(&dev_info, 0, sizeof(dev_info));
> > dev_info.device_id = dev->pdev->device;
> > dev_info.chip_rev = adev->rev_id;
> > dev_info.external_rev = adev->external_rev_id;
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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