Message-ID: <bea70e02-2d1b-4fc5-bcb0-b1bf33c09139@amd.com>
Date: Mon, 3 Nov 2025 15:09:44 -0600
From: Mario Limonciello <mario.limonciello@....com>
To: Rong Zhang <i@...g.moe>, Harry Wentland <harry.wentland@....com>,
 Leo Li <sunpeng.li@....com>, Rodrigo Siqueira <siqueira@...lia.com>,
 Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: Roman Li <roman.li@....com>,
 "ChiaHsuan (Tom) Chung" <chiahsuan.chung@....com>, Ray Wu <ray.wu@....com>,
 Wenjing Liu <wenjing.liu@....com>,
 Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>,
 Aurabindo Pillai <aurabindo.pillai@....com>, amd-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: Fix NULL deref in debugfs
 odm_combine_segments



On 11/3/2025 12:15 PM, Rong Zhang wrote:
> Hi all,
> 
> On Tue, 2025-10-14 at 00:47 +0800, Rong Zhang wrote:
>> When a connector is connected but inactive (e.g., disabled by desktop
>> environments), pipe_ctx->stream_res.tg will be destroyed. Then, reading
>> odm_combine_segments causes kernel NULL pointer dereference.
>>
>>   BUG: kernel NULL pointer dereference, address: 0000000000000000
>>   #PF: supervisor read access in kernel mode
>>   #PF: error_code(0x0000) - not-present page
>>   PGD 0 P4D 0
>>   Oops: Oops: 0000 [#1] SMP NOPTI
>>   CPU: 16 UID: 0 PID: 26474 Comm: cat Not tainted 6.17.0+ #2 PREEMPT(lazy)  e6a17af9ee6db7c63e9d90dbe5b28ccab67520c6
>>   Hardware name: LENOVO 21Q4/LNVNB161216, BIOS PXCN25WW 03/27/2025
>>   RIP: 0010:odm_combine_segments_show+0x93/0xf0 [amdgpu]
>>   Code: 41 83 b8 b0 00 00 00 01 75 6e 48 98 ba a1 ff ff ff 48 c1 e0 0c 48 8d 8c 07 d8 02 00 00 48 85 c9 74 2d 48 8b bc 07 f0 08 00 00 <48> 8b 07 48 8b 80 08 02 00>
>>   RSP: 0018:ffffd1bf4b953c58 EFLAGS: 00010286
>>   RAX: 0000000000005000 RBX: ffff8e35976b02d0 RCX: ffff8e3aeed052d8
>>   RDX: 00000000ffffffa1 RSI: ffff8e35a3120800 RDI: 0000000000000000
>>   RBP: 0000000000000000 R08: ffff8e3580eb0000 R09: ffff8e35976b02d0
>>   R10: ffffd1bf4b953c78 R11: 0000000000000000 R12: ffffd1bf4b953d08
>>   R13: 0000000000040000 R14: 0000000000000001 R15: 0000000000000001
>>   FS:  00007f44d3f9f740(0000) GS:ffff8e3caa47f000(0000) knlGS:0000000000000000
>>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>   CR2: 0000000000000000 CR3: 00000006485c2000 CR4: 0000000000f50ef0
>>   PKRU: 55555554
>>   Call Trace:
>>    <TASK>
>>    seq_read_iter+0x125/0x490
>>    ? __alloc_frozen_pages_noprof+0x18f/0x350
>>    seq_read+0x12c/0x170
>>    full_proxy_read+0x51/0x80
>>    vfs_read+0xbc/0x390
>>    ? __handle_mm_fault+0xa46/0xef0
>>    ? do_syscall_64+0x71/0x900
>>    ksys_read+0x73/0xf0
>>    do_syscall_64+0x71/0x900
>>    ? count_memcg_events+0xc2/0x190
>>    ? handle_mm_fault+0x1d7/0x2d0
>>    ? do_user_addr_fault+0x21a/0x690
>>    ? exc_page_fault+0x7e/0x1a0
>>    entry_SYSCALL_64_after_hwframe+0x6c/0x74
>>   RIP: 0033:0x7f44d4031687
>>   Code: 48 89 fa 4c 89 df e8 58 b3 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00>
>>   RSP: 002b:00007ffdb4b5f0b0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
>>   RAX: ffffffffffffffda RBX: 00007f44d3f9f740 RCX: 00007f44d4031687
>>   RDX: 0000000000040000 RSI: 00007f44d3f5e000 RDI: 0000000000000003
>>   RBP: 0000000000040000 R08: 0000000000000000 R09: 0000000000000000
>>   R10: 0000000000000000 R11: 0000000000000202 R12: 00007f44d3f5e000
>>   R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000040000
>>    </TASK>
>>   Modules linked in: tls tcp_diag inet_diag xt_mark ccm snd_hrtimer snd_seq_dummy snd_seq_midi snd_seq_oss snd_seq_midi_event snd_rawmidi snd_seq snd_seq_device x>
>>    snd_hda_codec_atihdmi snd_hda_codec_realtek_lib lenovo_wmi_helpers think_lmi snd_hda_codec_generic snd_hda_codec_hdmi snd_soc_core kvm snd_compress uvcvideo sn>
>>    platform_profile joydev amd_pmc mousedev mac_hid sch_fq_codel uinput i2c_dev parport_pc ppdev lp parport nvme_fabrics loop nfnetlink ip_tables x_tables dm_cryp>
>>   CR2: 0000000000000000
>>   ---[ end trace 0000000000000000 ]---
>>   RIP: 0010:odm_combine_segments_show+0x93/0xf0 [amdgpu]
>>   Code: 41 83 b8 b0 00 00 00 01 75 6e 48 98 ba a1 ff ff ff 48 c1 e0 0c 48 8d 8c 07 d8 02 00 00 48 85 c9 74 2d 48 8b bc 07 f0 08 00 00 <48> 8b 07 48 8b 80 08 02 00>
>>   RSP: 0018:ffffd1bf4b953c58 EFLAGS: 00010286
>>   RAX: 0000000000005000 RBX: ffff8e35976b02d0 RCX: ffff8e3aeed052d8
>>   RDX: 00000000ffffffa1 RSI: ffff8e35a3120800 RDI: 0000000000000000
>>   RBP: 0000000000000000 R08: ffff8e3580eb0000 R09: ffff8e35976b02d0
>>   R10: ffffd1bf4b953c78 R11: 0000000000000000 R12: ffffd1bf4b953d08
>>   R13: 0000000000040000 R14: 0000000000000001 R15: 0000000000000001
>>   FS:  00007f44d3f9f740(0000) GS:ffff8e3caa47f000(0000) knlGS:0000000000000000
>>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>   CR2: 0000000000000000 CR3: 00000006485c2000 CR4: 0000000000f50ef0
>>   PKRU: 55555554
>>
>> Fix this by checking pipe_ctx->stream_res.tg before dereferencing.
>>
>> Fixes: 07926ba8a44f ("drm/amd/display: Add debugfs interface for ODM combine info")
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Rong Zhang <i@...g.moe>
>> ---
>>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
>> index f263e1a4537e1..00dac862b665a 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c
>> @@ -1302,7 +1302,8 @@ static int odm_combine_segments_show(struct seq_file *m, void *unused)
>>   	if (connector->status != connector_status_connected)
>>   		return -ENODEV;
>>   
>> -	if (pipe_ctx != NULL && pipe_ctx->stream_res.tg->funcs->get_odm_combine_segments)
>> +	if (pipe_ctx && pipe_ctx->stream_res.tg &&
>> +	    pipe_ctx->stream_res.tg->funcs->get_odm_combine_segments)
>>   		pipe_ctx->stream_res.tg->funcs->get_odm_combine_segments(pipe_ctx->stream_res.tg, &segments);
>>   
>>   	seq_printf(m, "%d\n", segments);
>>
>> base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787
> 
> Gentle ping.
> 
> Thanks,
> Rong

Reviewed-by: Mario Limonciello <mario.limonciello@....com>

And applied, thanks.

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