[Linux-kernel-mentees] [PATCH] drm/amdgpu: Prevent kernel-infoleak in amdgpu_info_ioctl()
Alex Deucher
alexdeucher at gmail.com
Wed Jul 29 13:49:40 UTC 2020
On Wed, Jul 29, 2020 at 4:11 AM Christian König
<ckoenig.leichtzumerken at gmail.com> 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 at vger.kernel.org
> > Fixes: c193fa91b918 ("drm/amdgpu: information leak in amdgpu_info_ioctl()")
> > Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
> > Suggested-by: Dan Carpenter <dan.carpenter at oracle.com>
> > Signed-off-by: Peilin Ye <yepeilin.cs at gmail.com>
>
> Reviewed-by: Christian König <christian.koenig at amd.com>
>
> 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.
Moreover, it seems like different compilers seem to behave relatively
differently with these and we often get reports of warnings with these
on clang. When in doubt, memset.
Alex
>
> 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;
>
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