CVE-2021-3489

Published: 11 May 2021

The eBPF RINGBUF bpf_ringbuf_reserve() function in the Linux kernel did not check that the allocated size was smaller than the ringbuf size, allowing an attacker to perform out-of-bounds writes within the kernel and therefore, arbitrary code execution. This issue was fixed via commit 4b81ccebaeee ("bpf, ringbuf: Deny reserve of buffers larger than ringbuf") (v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and v5.10.37. It was introduced via 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") (v5.8-rc1).

From the Ubuntu Security Team

Ryota Shiga discovered that the eBPF implementation in the Linux kernel did not properly verify that a BPF program only reserved as much memory for a ring buffer as was allocated. A local attacker could use this to cause a denial of service (system crash) or execute arbitrary code.

Notes

introduced in v5.8-rc1

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3489
• https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=4b81ccebaeee885ab1aa1438133f2991e3a2b6ea
• https://www.openwall.com/lists/oss-security/2021/05/11/10
• https://ubuntu.com/security/notices/USN-4948-1
• https://ubuntu.com/security/notices/USN-4949-1
• https://ubuntu.com/security/notices/USN-4950-1
• NVD
• Launchpad
• Debian