Bug 2395788 (CVE-2025-39807)

Summary: CVE-2025-39807 kernel: drm/mediatek: Add error handling for old state CRTC in atomic_disable
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-09-16 14:02:30 UTC 
In the Linux kernel, the following vulnerability has been resolved:

drm/mediatek: Add error handling for old state CRTC in atomic_disable

Introduce error handling to address an issue where, after a hotplug
event, the cursor continues to update. This situation can lead to a
kernel panic due to accessing the NULL `old_state->crtc`.

E,g.
Unable to handle kernel NULL pointer dereference at virtual address
Call trace:
 mtk_crtc_plane_disable+0x24/0x140
 mtk_plane_atomic_update+0x8c/0xa8
 drm_atomic_helper_commit_planes+0x114/0x2c8
 drm_atomic_helper_commit_tail_rpm+0x4c/0x158
 commit_tail+0xa0/0x168
 drm_atomic_helper_commit+0x110/0x120
 drm_atomic_commit+0x8c/0xe0
 drm_atomic_helper_update_plane+0xd4/0x128
 __setplane_atomic+0xcc/0x110
 drm_mode_cursor_common+0x250/0x440
 drm_mode_cursor_ioctl+0x44/0x70
 drm_ioctl+0x264/0x5d8
 __arm64_sys_ioctl+0xd8/0x510
 invoke_syscall+0x6c/0xe0
 do_el0_svc+0x68/0xe8
 el0_svc+0x34/0x60
 el0t_64_sync_handler+0x1c/0xf8
 el0t_64_sync+0x180/0x188

Adding NULL pointer checks to ensure stability by preventing operations
on an invalid CRTC state.
Comment 1 Keith Grant 2025-09-16 15:16:57 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025091613-CVE-2025-39807-4c3b@gregkh/T