On Sep 10, 2015 5:22 PM, "Tycho Andersen" <tycho.ander...@canonical.com> wrote:
>
> This patch adds a way for a process that is "real root" to access the
> seccomp filters of another process. The process first does a
> PTRACE_SECCOMP_GET_FILTER_FD to get an fd with that process' seccomp filter
> attached, and then iterates on this with PTRACE_SECCOMP_NEXT_FILTER using
> bpf(BPF_PROG_DUMP) to dump the actual program at each step.
>
> +
> + fd = bpf_new_fd(filter->prog, O_RDONLY);
> + if (fd > 0)
> + atomic_inc(&filter->prog->aux->refcnt);
Why isn't this folded into bpf_new_fd?
> +
> + return fd;
> +}
> +
> +long seccomp_next_filter(struct task_struct *child, u32 fd)
> +{
> + struct seccomp_filter *cur;
> + struct bpf_prog *prog;
> + long ret = -ESRCH;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EACCES;
> +
> + if (child->seccomp.mode != SECCOMP_MODE_FILTER)
> + return -EINVAL;
> +
> + prog = bpf_prog_get(fd);
> + if (IS_ERR(prog)) {
> + ret = PTR_ERR(prog);
> + goto out;
> + }
> +
> + for (cur = child->seccomp.filter; cur; cur = cur->prev) {
> + if (cur->prog == prog) {
> + if (!cur->prev)
> + ret = -ENOENT;
> + else
> + ret = bpf_prog_set(fd, cur->prev->prog);
This lets you take an fd pointing to one prog and point it elsewhere.
I'm not sure that's a good idea.
--Andy
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