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

bpf: Reject non-negative offsets in stack slot obj get spi()

bpf get spi() computes (-off - 1) / BPF REG SIZE using C division, which truncates toward zero. For off == 0, this produces spi 0, the same index used by the valid stack slot at fp-8.

stack slot obj get spi() currently checks alignment and the resulting spi bounds, but does not reject the non-negative offset itself. It can therefore validate a PTR TO STACK register holding fp+0 against an iterator stored at fp-8 even though the runtime receives the actual fp+0 pointer. An effectful iterator kfunc can then interpret memory outside the BPF stack as iterator state.

Reject non-negative offsets before converting the offset to an spi. All valid stack objects begin at a negative offset from the frame pointer.