CVE-2024-42072

In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix may_goto with negative offset.

Zac's syzbot crafted a bpf prog that exposed two bugs in may_goto.

The 1st bug is the way may_goto is patched. When offset is negative

it should be patched differently.

The 2nd bug is in the verifier:

when current state may_goto_depth is equal to visited state may_goto_depth

it means there is an actual infinite loop. It's not correct to prune

exploration of the program at this point.

Note, that this check doesn't limit the program to only one may_goto insn,

since 2nd and any further may_goto will increment may_goto_depth only

in the queued state pushed for future exploration. The current state

will have may_goto_depth == 0 regardless of number of may_goto insns

and the verifier has to explore the program until bpf_exit.