====================
bpf: Fix array bounds error with may_goto and add selftest
Syzbot caught an array out-of-bounds bug [1]. It turns out that when the
BPF program runs through do_misc_fixups(), it allocates an extra 8 bytes
on the call stack, which eventually causes stack_depth to exceed 512.
I was able to reproduce this issue probabilistically by enabling
CONFIG_UBSAN=y and disabling CONFIG_BPF_JIT_ALWAYS_ON with the selfttest
I provide in second patch(although it doesn't happen every time - I didn't
dig deeper into why UBSAN behaves this way).
Furthermore, if I set /proc/sys/net/core/bpf_jit_enable to 0 to disable
the jit, a panic occurs, and the reason is the same, that bpf_func is
assigned an incorrect address.
v1 -> v2:
Directly reject loading programs with a stack size greater than 512 when
jit disabled.(Suggested by Alexei Starovoitov)
https://lore.kernel.org/bpf/20250212135251.85487-1-mrpre@163.com/T/
====================