bpf: Reject negative optlen in cgroup getsockopt hook

Summary

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.

Timeline

1. Sep 17, 2026, 4:06 PM UTCCVE published
2. Oct 19, 2026, 8:58 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 08f61a34913558e06576e7b6318bf583f273c1be · fixed in 5b09d984b38b018b123c3a9e02a96bbc6468dbe5; From 9cacf81f8161111db25f98e78a7a0e32ae142b3f · fixed in 554ba7195c4108726450e24480c8449990c2268c; From 9cacf81f8161111db25f98e78a7a0e32ae142b3f · fixed in d02a12b4085ffe41ea750b1007f7a9c7aee2875a; From 9cacf81f8161111db25f98e78a7a0e32ae142b3f · fixed in e6fbf0eba87f50084d67508898f6ad6fc7ff1ba2; From 9cacf81f8161111db25f98e78a7a0e32ae142b3f · fixed in f68671b1a98d426c57864bd457c125fee14ac1a5; From 9cacf81f8161111db25f98e78a7a0e32ae142b3f · fixed in 2bdbe00454200fcb0110f31eeca8d906a3515e74; From 9cacf81f8161111db25f98e78a7a0e32ae142b3f · fixed in 31a89af4f513d750fec196e2bb6195a7d4473e9f; From 9cacf81f8161111db25f98e78a7a0e32ae142b3f · fixed in 1b5aacd5b2419b0790e955e466d389a61c79b4b1; From 5.10.188 · fixed in 5.10.270

• Linux Linux

  5.12

• KernelLinux

  fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.12.0 · fixed in 6.1.188; From 5.16.0 · fixed in 6.6.157; From 6.2.0 · fixed in 6.12.110; From 6.7.0 · fixed in 6.18.52; From 6.13.0 · fixed in 7.2.6

References 8