bpf: Fix issue in verifying allow_ptr_leaks

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix issue in verifying allow_ptr_leaks After we converted the capabilities of our networking-bpf program from cap_sys_admin to cap_net_admin+cap_bpf, our networking-bpf program failed to start. Because it failed the bpf verifier, and the error log is "R3 pointer comparison prohibited". A simple reproducer as follows, SEC("cls-ingress") int ingress(struct __sk_buff *skb) { struct iphdr *iph = (void *)(long)skb->data + sizeof(struct ethhdr); if ((long)(iph + 1) > (long)skb->data_end) return TC_ACT_STOLEN; return TC_ACT_OK; } Per discussion with Yonghong and Alexei [1], comparison of two packet pointers is not a pointer leak. This patch fixes it. Our local kernel is 6.1.y and we expect this fix to be backported to 6.1.y, so stable is CCed. [1]. https://lore.kernel.org/bpf/CAADnVQ+Nmspr7Si+pxWn8zkE7hX-7s93ugwC+94aXSy4uQ9vBg@mail.gmail.com/

References

• https://git.kernel.org/stable/c/c96c67991aac6401b4c6996093bccb704bb2ea4b
• https://git.kernel.org/stable/c/5927f0172d2809d8fc09c1ba667280b0387e9f73
• https://git.kernel.org/stable/c/acfdc8b77016c8e648aadc283177546c88083dd3
• https://git.kernel.org/stable/c/d75e30dddf73449bc2d10bb8e2f1a2c446bc67a2