CVE-2024-50163 Information

Description

In the Linux kernel the following vulnerability has been resolved:

bpf: Make sure internal and UAPI bpf_redirect flags don’t overlap

The bpf_redirect_info is shared between the SKB and XDP redirect paths and the two paths use the same numeric flag values in the ri->flags field (specifically BPF_F_BROADCAST == BPF_F_NEXTHOP). This means that if skb bpf_redirect_neigh() is used with a non-NULL params argument and subsequently an XDP redirect is performed using the same bpf_redirect_info struct the XDP path will get confused and end up crashing which syzbot managed to trigger.

With the stack-allocated bpf_redirect_info the structure is no longer shared between the SKB and XDP paths so the crash doesn’t happen anymore. However different code paths using identically-numbered flag values in the same struct field still seems like a bit of a mess so this patch cleans that up by moving the flag definitions together and redefining the three flags in BPF_F_REDIRECT_INTERNAL to not overlap with the flags used for XDP. It also adds a BUILD_BUG_ON() check to make sure the overlap is not re-introduced by mistake.

Reference

https://git.kernel.org/stable/c/4e1e428533845d48828bd3875c0e92e8565b9962 https://git.kernel.org/stable/c/314dbee9fe4f5cee36435465de52c988d7caa466 https://git.kernel.org/stable/c/0fca5ed4be8e8bfbfb9bd97845af596bab7192d3 https://git.kernel.org/stable/c/cec288e05ceac9a0d3a3a1fd279534b11844c826 https://git.kernel.org/stable/c/09d88791c7cd888d5195c84733caf9183dcfbd16