bpf: Fix memleak due to fentry attach failure

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix memleak due to fentry attach failure If it fails to attach fentry, the allocated bpf trampoline image will be left in the system. That can be verified by checking /proc/kallsyms. This meamleak can be verified by a simple bpf program as follows: SEC("fentry/trap_init") int fentry_run() { return 0; } It will fail to attach trap_init because this function is freed after kernel init, and then we can find the trampoline image is left in the system by checking /proc/kallsyms. $ tail /proc/kallsyms ffffffffc0613000 t bpf_trampoline_6442453466_1 [bpf] ffffffffc06c3000 t bpf_trampoline_6442453466_1 [bpf] $ bpftool btf dump file /sys/kernel/btf/vmlinux | grep "FUNC 'trap_init'" [2522] FUNC 'trap_init' type_id=119 linkage=static $ echo $((6442453466 & 0x7fffffff)) 2522 Note that there are two left bpf trampoline images, that is because the libbpf will fallback to raw tracepoint if -EINVAL is returned.

References

• https://git.kernel.org/stable/c/20109ddd5bea2c24d790debf5d02584ef24c3f5e
• https://git.kernel.org/stable/c/f72c67d1a82dada7d6d504c806e111e913721a30
• https://git.kernel.org/stable/c/6aa27775db63ba8c7c73891c7dfb71ddc230c48d
• https://git.kernel.org/stable/c/108598c39eefbedc9882273ac0df96127a629220