[PATCH] drm/ttm: fix undefined behavior in bit shift for TTM_TT_FLAG_PRIV_POPULATED

[Christian König]

Am 31.10.22 um 12:33 schrieb Gaosheng Cui:
> Shifting signed 32-bit value by 31 bits is undefined, so changing
> significant bit to unsigned. The UBSAN warning calltrace like below:
>
> UBSAN: shift-out-of-bounds in ./include/drm/ttm/ttm_tt.h:122:26
> left shift of 1 by 31 places cannot be represented in type 'int'
> Call Trace:
>   <TASK>
>   dump_stack_lvl+0x7d/0xa5
>   dump_stack+0x15/0x1b
>   ubsan_epilogue+0xe/0x4e
>   __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
>   ttm_bo_move_memcpy+0x3b4/0x460 [ttm]
>   bo_driver_move+0x32/0x40 [drm_vram_helper]
>   ttm_bo_handle_move_mem+0x118/0x200 [ttm]
>   ttm_bo_validate+0xfa/0x220 [ttm]
>   drm_gem_vram_pin_locked+0x70/0x1b0 [drm_vram_helper]
>   drm_gem_vram_pin+0x48/0xb0 [drm_vram_helper]
>   drm_gem_vram_plane_helper_prepare_fb+0x53/0xe0 [drm_vram_helper]
>   drm_gem_vram_simple_display_pipe_prepare_fb+0x26/0x30 [drm_vram_helper]
>   drm_simple_kms_plane_prepare_fb+0x4d/0xe0 [drm_kms_helper]
>   drm_atomic_helper_prepare_planes+0xda/0x210 [drm_kms_helper]
>   drm_atomic_helper_commit+0xc3/0x1e0 [drm_kms_helper]
>   drm_atomic_commit+0x9c/0x160 [drm]
>   drm_client_modeset_commit_atomic+0x33a/0x380 [drm]
>   drm_client_modeset_commit_locked+0x77/0x220 [drm]
>   drm_client_modeset_commit+0x31/0x60 [drm]
>   __drm_fb_helper_restore_fbdev_mode_unlocked+0xa7/0x170 [drm_kms_helper]
>   drm_fb_helper_set_par+0x51/0x90 [drm_kms_helper]
>   fbcon_init+0x316/0x790
>   visual_init+0x113/0x1d0
>   do_bind_con_driver+0x2a3/0x5c0
>   do_take_over_console+0xa9/0x270
>   do_fbcon_takeover+0xa1/0x170
>   do_fb_registered+0x2a8/0x340
>   fbcon_fb_registered+0x47/0xe0
>   register_framebuffer+0x294/0x4a0
>   __drm_fb_helper_initial_config_and_unlock+0x43c/0x880 [drm_kms_helper]
>   drm_fb_helper_initial_config+0x52/0x80 [drm_kms_helper]
>   drm_fbdev_client_hotplug+0x156/0x1b0 [drm_kms_helper]
>   drm_fbdev_generic_setup+0xfc/0x290 [drm_kms_helper]
>   bochs_pci_probe+0x6ca/0x772 [bochs]
>   local_pci_probe+0x4d/0xb0
>   pci_device_probe+0x119/0x320
>   really_probe+0x181/0x550
>   __driver_probe_device+0xc6/0x220
>   driver_probe_device+0x32/0x100
>   __driver_attach+0x195/0x200
>   bus_for_each_dev+0xbb/0x120
>   driver_attach+0x27/0x30
>   bus_add_driver+0x22e/0x2f0
>   driver_register+0xa9/0x190
>   __pci_register_driver+0x90/0xa0
>   bochs_pci_driver_init+0x52/0x1000 [bochs]
>   do_one_initcall+0x76/0x430
>   do_init_module+0x61/0x28a
>   load_module+0x1f82/0x2e50
>   __do_sys_finit_module+0xf8/0x190
>   __x64_sys_finit_module+0x23/0x30
>   do_syscall_64+0x58/0x80
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>   </TASK>
>
> Fixes: 3312be8f6fc8 ("drm/ttm: move populated state into page flags")
> Signed-off-by: Gaosheng Cui <cuigaosheng1 at huawei.com>

Reviewed-by: Christian König <christian.koenig at amd.com>

Going to push this to drm-misc-next.

Thanks,
Christian.

> ---
>   include/drm/ttm/ttm_tt.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/drm/ttm/ttm_tt.h b/include/drm/ttm/ttm_tt.h
> index 17a0310e8aaa..b7d3f3843f1e 100644
> --- a/include/drm/ttm/ttm_tt.h
> +++ b/include/drm/ttm/ttm_tt.h
> @@ -88,7 +88,7 @@ struct ttm_tt {
>   #define TTM_TT_FLAG_EXTERNAL		(1 << 2)
>   #define TTM_TT_FLAG_EXTERNAL_MAPPABLE	(1 << 3)
>   
> -#define TTM_TT_FLAG_PRIV_POPULATED  (1 << 31)
> +#define TTM_TT_FLAG_PRIV_POPULATED  (1U << 31)
>   	uint32_t page_flags;
>   	/** @num_pages: Number of pages in the page array. */
>   	uint32_t num_pages;