In the Linux kernel, the following vulnerability has been resolved:
bpf: Reject negative optlen in cgroup getsockopt hook
A cgroup getsockopt BPF program can shrink ctx->optlen after the
kernel getsockopt handler has run. The kernel-buffer variant, used by
TCP_ZEROCOPY_RECEIVE, only rejects values larger than the original
length.
If BPF writes a negative optlen, that value is accepted and propagated
back to the TCP getsockopt code. It can then be passed to
copy_to_sockptr() as a size_t and trigger the hardened usercopy
bytes > INT_MAX warning.
Reject negative ctx.optlen in __cgroup_bpf_run_filter_getsockopt_kern(),
matching the lower-bound validation already present in the sockptr-based
getsockopt hook.
