Alex Hung 9d1a65cbe3 drm/amd/display: Check NULL before accessing
commit 3ce62c189693e8ed7b3abe551802bbc67f3ace54 upstream.

[WHAT]
IGT kms_cursor_legacy's long-nonblocking-modeset-vs-cursor-atomic
fails with NULL pointer dereference. This can be reproduced with
both an eDP panel and a DP monitors connected.

 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: 13 UID: 0 PID: 2960 Comm: kms_cursor_lega Not tainted
6.16.0-99-custom #8 PREEMPT(voluntary)
 Hardware name: AMD ........
 RIP: 0010:dc_stream_get_scanoutpos+0x34/0x130 [amdgpu]
 Code: 57 4d 89 c7 41 56 49 89 ce 41 55 49 89 d5 41 54 49
 89 fc 53 48 83 ec 18 48 8b 87 a0 64 00 00 48 89 75 d0 48 c7 c6 e0 41 30
 c2 <48> 8b 38 48 8b 9f 68 06 00 00 e8 8d d7 fd ff 31 c0 48 81 c3 e0 02
 RSP: 0018:ffffd0f3c2bd7608 EFLAGS: 00010292
 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffd0f3c2bd7668
 RDX: ffffd0f3c2bd7664 RSI: ffffffffc23041e0 RDI: ffff8b32494b8000
 RBP: ffffd0f3c2bd7648 R08: ffffd0f3c2bd766c R09: ffffd0f3c2bd7760
 R10: ffffd0f3c2bd7820 R11: 0000000000000000 R12: ffff8b32494b8000
 R13: ffffd0f3c2bd7664 R14: ffffd0f3c2bd7668 R15: ffffd0f3c2bd766c
 FS:  000071f631b68700(0000) GS:ffff8b399f114000(0000)
knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000000 CR3: 00000001b8105000 CR4: 0000000000f50ef0
 PKRU: 55555554
 Call Trace:
 <TASK>
 dm_crtc_get_scanoutpos+0xd7/0x180 [amdgpu]
 amdgpu_display_get_crtc_scanoutpos+0x86/0x1c0 [amdgpu]
 ? __pfx_amdgpu_crtc_get_scanout_position+0x10/0x10[amdgpu]
 amdgpu_crtc_get_scanout_position+0x27/0x50 [amdgpu]
 drm_crtc_vblank_helper_get_vblank_timestamp_internal+0xf7/0x400
 drm_crtc_vblank_helper_get_vblank_timestamp+0x1c/0x30
 drm_crtc_get_last_vbltimestamp+0x55/0x90
 drm_crtc_next_vblank_start+0x45/0xa0
 drm_atomic_helper_wait_for_fences+0x81/0x1f0
 ...

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 621e55f1919640acab25383362b96e65f2baea3c)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-12-07 06:18:53 +09:00
2022-09-28 09:02:20 +02:00
2025-12-01 11:41:54 +01:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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