[PATCH] drm/amd/display: Fix null pointer deref in dcn20_resource.c

[Rodrigo Siqueira Jordao]

On 6/26/24 11:16 AM, Aurabindo Pillai wrote:
> Fixes a hang that has the following calltrace:
> 
> [  181.843989] BUG: kernel NULL pointer dereference, address: 0000000000000000
> [  181.843997] #PF: supervisor instruction fetch in kernel mode
> [  181.844003] #PF: error_code(0x0010) - not-present page
> [  181.844009] PGD 0 P4D 0
> [  181.844020] Oops: 0010 [#1] PREEMPT SMP NOPTI
> [  181.844028] CPU: 6 PID: 1892 Comm: gnome-shell Tainted: G        W  OE      6.5.0-41-generic #41~22.04.2-Ubuntu
> [  181.844038] Hardware name: System manufacturer System Product Name/CROSSHAIR VI HERO, BIOS 6302 10/23/2018
> [  181.844044] RIP: 0010:0x0
> [  181.844079] Code: Unable to access opcode bytes at 0xffffffffffffffd6.
> [  181.844084] RSP: 0018:ffffb593c2b8f7b0 EFLAGS: 00010246
> [  181.844093] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000004
> [  181.844099] RDX: ffffb593c2b8f804 RSI: ffffb593c2b8f7e0 RDI: ffff9e3c8e758400
> [  181.844105] RBP: ffffb593c2b8f7b8 R08: ffffb593c2b8f9c8 R09: ffffb593c2b8f96c
> [  181.844110] R10: 0000000000000000 R11: 0000000000000000 R12: ffffb593c2b8f9c8
> [  181.844115] R13: 0000000000000001 R14: ffff9e3c88000000 R15: 0000000000000005
> [  181.844121] FS:  00007c6e323bb5c0(0000) GS:ffff9e3f85f80000(0000) knlGS:0000000000000000
> [  181.844128] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  181.844134] CR2: ffffffffffffffd6 CR3: 0000000140fbe000 CR4: 00000000003506e0
> [  181.844141] Call Trace:
> [  181.844146]  <TASK>
> [  181.844153]  ? show_regs+0x6d/0x80
> [  181.844167]  ? __die+0x24/0x80
> [  181.844179]  ? page_fault_oops+0x99/0x1b0
> [  181.844192]  ? do_user_addr_fault+0x31d/0x6b0
> [  181.844204]  ? exc_page_fault+0x83/0x1b0
> [  181.844216]  ? asm_exc_page_fault+0x27/0x30
> [  181.844237]  dcn20_get_dcc_compression_cap+0x23/0x30 [amdgpu]
> [  181.845115]  amdgpu_dm_plane_validate_dcc.constprop.0+0xe5/0x180 [amdgpu]
> [  181.845985]  amdgpu_dm_plane_fill_plane_buffer_attributes+0x300/0x580 [amdgpu]
> [  181.846848]  fill_dc_plane_info_and_addr+0x258/0x350 [amdgpu]
> [  181.847734]  fill_dc_plane_attributes+0x162/0x350 [amdgpu]
> [  181.848748]  dm_update_plane_state.constprop.0+0x4e3/0x6b0 [amdgpu]
> [  181.849791]  ? dm_update_plane_state.constprop.0+0x4e3/0x6b0 [amdgpu]
> [  181.850840]  amdgpu_dm_atomic_check+0xdfe/0x1760 [amdgpu]

Hi Jay,

Could you elaborate a little bit more on how to trigger this issue in 
the commit message?

> 
> Signed-off-by: Aurabindo Pillai <aurabindo.pillai at amd.com>
> ---
>   .../drm/amd/display/dc/resource/dcn20/dcn20_resource.c   | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn20/dcn20_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn20/dcn20_resource.c
> index e783afbbb397..645927496807 100644
> --- a/drivers/gpu/drm/amd/display/dc/resource/dcn20/dcn20_resource.c
> +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn20/dcn20_resource.c
> @@ -2200,10 +2200,11 @@ bool dcn20_get_dcc_compression_cap(const struct dc *dc,
>   		const struct dc_dcc_surface_param *input,
>   		struct dc_surface_dcc_cap *output)
>   {
> -	return dc->res_pool->hubbub->funcs->get_dcc_compression_cap(
> -			dc->res_pool->hubbub,
> -			input,
> -			output);
> +	if (dc->res_pool->hubbub->funcs->get_dcc_compression_cap)
> +		return dc->res_pool->hubbub->funcs->get_dcc_compression_cap(
> +			dc->res_pool->hubbub, input, output);

How about drop the 'else' and just return false?

Thanks
Siqueira

> +	else
> +		return false;
>   }
>   
>   static void dcn20_destroy_resource_pool(struct resource_pool **pool)