SB2021051155 - Ubuntu update for linux

Description

This security bulletin contains information about 3 secuirty vulnerabilities.

1) Out-of-bounds read (CVE-ID: CVE-2021-3489)

The vulnerability allows a local user to execute arbitrary code.

The vulnerability exists due to an out-of-bounds read error within the __bpf_ringbuf_reserve() function in kernel/bpf/ringbuf.c. A local user can execute arbitrary code.

2) Out-of-bounds write (CVE-ID: CVE-2021-3490)

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a boundary error when processing untrusted input in bpf. The eBPF ALU32 bounds tracking for bitwise ops (AND, OR and XOR) in the Linux kernel did not properly update 32-bit bounds, which could be turned into out of bounds reads and writes in the Linux kernel and therefore, arbitrary code execution. A local user can run a specially crafted program to trigger an out-of-bounds write and execute arbitrary code with elevated privileges.

3) Out-of-bounds write (CVE-ID: CVE-2021-3491)

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to the io_uring subsystem in the Linux kernel allowed the MAX_RW_COUNT limit to be bypassed in the PROVIDE_BUFFERS operation, which led to negative values being used in mem_rw when reading /proc/<PID>/mem. A local user can trigger a heap overflow and execute arbitrary code with elevated privileges.

Remediation

Install update from vendor's website.

References

• https://ubuntu.com/security/notices/USN-4950-1