CVE-2026-98590: bpf: Fix bpf_sock context code generation
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix bpfsock context code generation
Currently, the ctx access code reads the rxqueuemapping field with either a 4-byte or 2-byte load. The rest of the bits in the register are marked known zero by the verifier. However, the emitted ctx access code places in the register on certain the special value (-1) using BPFMOVIMM64, which gets sign-extended to turn on all the bits in the register. By shifting this value right, the program ends up with a value at runtime above what the verifier assumes is possible.
Fix this by ensuring the read value is as wide as the assumed size. Use MOV32 instructions instead of MOV64 instructions to keep the upper bits zero as assumed by the verifier. Also properly report the size of the destination variable (the bpfsock field, 4 bytes) instead of the source (the socket field, 2 bytes).
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Fix the bpf_sock context code generation by ensuring the ctx access read is as wide as the assumed destination size, and use MOV32 instructions instead of MOV64 instructions so the upper register bits remain known zero to the verifier.