CVE-2021-47165

What it actually does

Null pointer dereference in meson_drv_shutdown when the main component has not been probed, resulting in kernel panic on shutdown or reboot.

Why it matters to the business

Unexpected system crashes during shutdown or reboot on affected Linux kernels can cause service interruptions, potential data corruption, and require manual intervention to recover.

How an attack unfolds

An attacker with local access arranges for the dw-hdmi module to remain unloaded or in probe deferral, then initiates a shutdown or reboot; the kernel reaches meson_drv_shutdown without an allocated priv struct and dereferences a null pointer at offset 0x38, triggering a panic.

How to fix it

Apply the upstream fix that adds a check for an allocated priv struct before use in meson_drv_shutdown; update to a kernel containing commit resolving CVE-2021-47165.

How to confirm the fix worked

Inspect the meson_drv.c source for the added priv pointer check before access; confirm the patch is present via kernel source or binary analysis and test shutdown behavior under probe-defer conditions.

Typical attack path

1. Obtain local access to the target system
2. Ensure the dw-hdmi module is not loaded or deferred
3. Trigger kernel_restart or system shutdown
4. meson_drv_shutdown dereferences uninitialized priv pointer
5. Kernel panics with NULL pointer dereference

How to detect it

Search kernel panic logs and dmesg for strings referencing meson_drv_shutdown and NULL pointer dereference at virtual address 0000000000000038; correlate with shutdown or reboot events when dw-hdmi is absent.

• meson_drv_shutdown+0x24/0x50
• Unable to handle kernel NULL pointer dereference at virtual address 0000000000000038
• pc : meson_drv_shutdown+0x24/0x50

What your security team should do

• Prioritize kernel updates for systems using Meson DRM hardware
• Review boot logs for dw-hdmi probe failures before enabling automatic reboots
• Incorporate similar driver null-check patterns into internal kernel hardening reviews