• Ard Biesheuvel's avatar
    arm64/bpf: don't allocate BPF JIT programs in module memory · 91fc957c
    Ard Biesheuvel authored
    The arm64 module region is a 128 MB region that is kept close to
    the core kernel, in order to ensure that relative branches are
    always in range. So using the same region for programs that do
    not have this restriction is wasteful, and preferably avoided.
    
    Now that the core BPF JIT code permits the alloc/free routines to
    be overridden, implement them by vmalloc()/vfree() calls from a
    dedicated 128 MB region set aside for BPF programs. This ensures
    that BPF programs are still in branching range of each other, which
    is something the JIT currently depends upon (and is not guaranteed
    when using module_alloc() on KASLR kernels like we do currently).
    It also ensures that placement of BPF programs does not correlate
    with the placement of the core kernel or modules, making it less
    likely that leaking the former will reveal the latter.
    
    This also solves an issue under KASAN, where shadow memory is
    needlessly allocated for all BPF programs (which don't require KASAN
    shadow pages since they are not KASAN instrumented)
    Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
    Acked-by: default avatarWill Deacon <will.deacon@arm.com>
    Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
    91fc957c
bpf_jit_comp.c 24.1 KB