CVE-2021-47608: In the Linux kernel, the following vulnerability has been resolved: bpf: Fix kernel address leakage in atomic fetch Th

The source recommends: "One minimally intrusive option to fix the leak is for the BPF_FETCH case to initially check the BPF_READ case via check_mem_access() with -1 as register, followed by the actual load case with non-negative load_reg to propagate stack bounds to registers." In other words, the kernel should perform two checks in sequence when handling atomic fetch operations: first a read check using a placeholder value (-1), then a second check with the actual register value to properly handle stack data propagation.