bpf: consider that tail calls invalidate packet pointers

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: consider that tail calls invalidate packet pointers Tail-called programs could execute any of the helpers that invalidate packet pointers. Hence, conservatively assume that each tail call invalidates packet pointers. Making the change in bpf_helper_changes_pkt_data() automatically makes use of check_cfg() logic that computes 'changes_pkt_data' effect for global sub-programs, such that the following program could be rejected: int tail_call(struct __sk_buff *sk) { bpf_tail_call_static(sk, &jmp_table, 0); return 0; } SEC("tc") int not_safe(struct __sk_buff *sk) { int p = (void )(long)sk->data; ... make p valid ... tail_call(sk); p = 42; / this is unsafe */ ... } The tc_bpf2bpf.c:subprog_tc() needs change: mark it as a function that can invalidate packet pointers. Otherwise, it can't be freplaced with tailcall_freplace.c:entry_freplace() that does a tail call.

Timeline

1. May 5, 2025, 2:53 PM UTCCVE published
2. Oct 15, 2026, 9:42 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 15, 2026, 9:51 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 51c39bb1d5d105a02e29aa7960f0a395086e6342 · fixed in f1692ee23dcaaddc24ba407b269707ee5df1301f; From 51c39bb1d5d105a02e29aa7960f0a395086e6342 · fixed in 1c2244437f9ad3dd91215f920401a14f2542dbfc; From 51c39bb1d5d105a02e29aa7960f0a395086e6342 · fixed in 1a4607ffba35bf2a630aab299e34dd3f6e658d70

• Linux Linux

  5.6

• KernelLinux

  From 5.6.0 · fixed in 6.6.90; From 6.7.0 · fixed in 6.12.9

References 3