CVE-2021-47264

What it actually does

Null pointer dereference due to unchecked return value from devm_kstrdup in fmt_single_name within the ASoC core of the Linux kernel.

Why it matters to the business

Unexpected kernel crashes in audio subsystems can interrupt sound services, force reboots, and reduce system reliability for devices relying on ALSA.

How an attack unfolds

An attacker triggers memory allocation failure under specific conditions in the ALSA sound subsystem, causing fmt_single_name to dereference a null pointer and panic the kernel.

How to fix it

Apply Linux kernel updates that add the missing null check after the devm_kstrdup call in fmt_single_name.

How to confirm the fix worked

Inspect kernel source for the presence of a return-value check immediately following the devm_kstrdup invocation inside fmt_single_name.

Typical attack path

1. Induce memory pressure or allocation failure conditions
2. Invoke code paths reaching fmt_single_name in ASoC core
3. Trigger null dereference leading to kernel panic

How to detect it

Search kernel logs and oops reports for references to fmt_single_name combined with null pointer dereference messages in ASoC contexts.

• fmt_single_name
• devm_kstrdup
• ASoC.*null pointer dereference

What your security team should do

• Prioritize kernel package updates on all affected systems
• Review audio subsystem crash logs for patterns matching the dereference
• Test updated kernels in staging environments before broad deployment