CVE-2024-47703

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

bpf, lsm: Add check for BPF LSM return value

A bpf prog returning a positive number attached to file_alloc_security

hook makes kernel panic.

This happens because file system can not filter out the positive number

returned by the LSM prog using IS_ERR, and misinterprets this positive

number as a file pointer.

Given that hook file_alloc_security never returned positive number

before the introduction of BPF LSM, and other BPF LSM hooks may

encounter similar issues, this patch adds LSM return value check

in verifier, to ensure no unexpected value is returned.