• Alexei Starovoitov's avatar
    bpf: introduce BPF_F_ALLOW_OVERRIDE flag · 7f677633
    Alexei Starovoitov authored
    If BPF_F_ALLOW_OVERRIDE flag is used in BPF_PROG_ATTACH command
    to the given cgroup the descendent cgroup will be able to override
    effective bpf program that was inherited from this cgroup.
    By default it's not passed, therefore override is disallowed.
    
    Examples:
    1.
    prog X attached to /A with default
    prog Y fails to attach to /A/B and /A/B/C
    Everything under /A runs prog X
    
    2.
    prog X attached to /A with allow_override.
    prog Y fails to attach to /A/B with default (non-override)
    prog M attached to /A/B with allow_override.
    Everything under /A/B runs prog M only.
    
    3.
    prog X attached to /A with allow_override.
    prog Y fails to attach to /A with default.
    The user has to detach first to switch the mode.
    
    In the future this behavior may be extended with a chain of
    non-overridable programs.
    
    Also fix the bug where detach from cgroup where nothing is attached
    was not throwing error. Return ENOENT in such case.
    
    Add several testcases and adjust libbpf.
    
    Fixes: 30070984 ("cgroup: add support for eBPF programs")
    Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
    Acked-by: default avatarTejun Heo <tj@kernel.org>
    Acked-by: default avatarDaniel Mack <daniel@zonque.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    7f677633
bpf.c 4.55 KB