CVE-2016-7910

What it actually does

Use-after-free in disk_seqf_stop allows a local process to access and control freed kernel memory structures after a failed start operation, enabling privilege escalation to root.

Why it matters to the business

Attackers with local access can fully compromise the system, install persistent malware, access all data, and move laterally; older unpatched kernels remain exposed years after disclosure.

How an attack unfolds

An attacker invokes a disk sequence operation that fails at start yet still executes the stop handler, triggering the use-after-free; they then spray controlled data into the freed slab and hijack execution flow to execute arbitrary kernel code.

How to fix it

Upgrade the Linux kernel to version 4.7.1 or later, or apply commit 77da160530dd1dc94f6ae15a981f24e5f0021e84; rebuild and reboot into the fixed kernel; where immediate patching is impossible, restrict untrusted local accounts and disable unnecessary block device access.

How to confirm the fix worked

Verify running kernel version is 4.7.1 or newer; confirm the presence of commit 77da160530dd1dc94f6ae15a981f24e5f0021e84 in the source tree; test that disk sequence operations no longer trigger the use-after-free condition via kernel fuzzing or static analysis.

Typical attack path

1. Obtain local shell on target Linux system
2. Trigger disk_seqf_start failure followed by stop operation
3. Perform heap grooming to reclaim freed memory with attacker-controlled data
4. Hijack function pointers or data structures to execute privilege-escalation payload
5. Spawn root shell or install persistent backdoor

How to detect it

Review kernel logs for oops or warning messages referencing disk_seqf_stop or genhd.c; correlate local user sessions with sudden root escalations or unexpected kernel module loads; examine audit logs for unusual block device open/close sequences preceding privilege changes.

What your security team should do

• Immediately upgrade all systems running kernels older than 4.7.1
• Prioritize systems that allow unprivileged local logins or run multi-tenant workloads
• Add kernel version checks to vulnerability scanning and asset inventory
• Harden local access controls and monitor for unexpected privilege changes until patches are deployed