drm/amdgpu: Fix integer overflow in amdgpu_gem_add_input_fence()

The "num_syncobj_handles" is a u32 value that comes from the user via the
ioctl. On 32bit systems the "sizeof(uint32_t) * num_syncobj_handles"
multiplication can have an integer overflow. Use size_mul() to fix that.

Fixes: 38c67ec9aa4b ("drm/amdgpu: Add input fence to sync bo map/unmap")
Signed-off-by: Dan Carpenter <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c

···
 		return 0;
 
 	syncobj_handles = memdup_user(u64_to_user_ptr(syncobj_handles_array),
-				      sizeof(uint32_t) * num_syncobj_handles);
+				      size_mul(sizeof(uint32_t), num_syncobj_handles));
 	if (IS_ERR(syncobj_handles))
 		return PTR_ERR(syncobj_handles);