• Tycho Andersen's avatar
    seccomp, ptrace: add support for dumping seccomp filters · f8e529ed
    Tycho Andersen authored
    This patch adds support for dumping a process' (classic BPF) seccomp
    filters via ptrace.
    
    PTRACE_SECCOMP_GET_FILTER allows the tracer to dump the user's classic BPF
    seccomp filters. addr should be an integer which represents the ith seccomp
    filter (0 is the most recently installed filter). data should be a struct
    sock_filter * with enough room for the ith filter, or NULL, in which case
    the filter is not saved. The return value for this command is the number of
    BPF instructions the program represents, or negative in the case of errors.
    Command specific errors are ENOENT: which indicates that there is no ith
    filter in this seccomp tree, and EMEDIUMTYPE, which indicates that the ith
    filter was not installed as a classic BPF filter.
    
    A caveat with this approach is that there is no way to get explicitly at
    the heirarchy of seccomp filters, and users need to memcmp() filters to
    decide which are inherited. This means that a task which installs two of
    the same filter can potentially confuse users of this interface.
    
    v2: * make save_orig const
        * check that the orig_prog exists (not necessary right now, but when
           grows eBPF support it will be)
        * s/n/filter_off and make it an unsigned long to match ptrace
        * count "down" the tree instead of "up" when passing a filter offset
    
    v3: * don't take the current task's lock for inspecting its seccomp mode
        * use a 0x42** constant for the ptrace command value
    
    v4: * don't copy to userspace while holding spinlocks
    
    v5: * add another condition to WARN_ON
    
    v6: * rebase on net-next
    Signed-off-by: default avatarTycho Andersen <tycho.andersen@canonical.com>
    Acked-by: default avatarKees Cook <keescook@chromium.org>
    CC: Will Drewry <wad@chromium.org>
    Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
    CC: Andy Lutomirski <luto@amacapital.net>
    CC: Pavel Emelyanov <xemul@parallels.com>
    CC: Serge E. Hallyn <serge.hallyn@ubuntu.com>
    CC: Alexei Starovoitov <ast@kernel.org>
    CC: Daniel Borkmann <daniel@iogearbox.net>
    Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    f8e529ed
seccomp.h 2.62 KB