CVE-2021-3490

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. This issue was fixed via commit 049c4e13714e
(“bpf: Fix alu32 const subreg bound tracking on bitwise operations”)
(v5.13-rc4) and backported to the stable kernels in v5.12.4, v5.11.21, and
v5.10.37. The AND/OR issues were introduced by commit 3f50f132d840 (“bpf:
Verifier, do explicit ALU32 bounds tracking”) (5.7-rc1) and the XOR variant
was introduced by 2921c90d4718 (“bpf:Fix a verifier failure with xor”) (
5.10-rc1).

Notes