Re: [RFC] bpf: Emit audit messages upon successful prog load and unload

From: Paul Moore <paul@paul-moore.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	linux-audit@redhat.com, Andrii Nakryiko <andriin@fb.com>,
	Yonghong Song <yhs@fb.com>, Martin KaFai Lau <kafai@fb.com>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Steve Grubb <sgrubb@redhat.com>, David Miller <davem@redhat.com>,
	Eric Paris <eparis@redhat.com>, Jiri Benc <jbenc@redhat.com>
Subject: Re: [RFC] bpf: Emit audit messages upon successful prog load and unload
Date: Wed, 4 Dec 2019 09:38:10 -0500	[thread overview]
Message-ID: <CAHC9VhTrUQYp8Ubhu_B_fv-HSdwmgYRy+r1p9uKz7WcRfDQBKA@mail.gmail.com> (raw)
In-Reply-To: <20191204140827.GB12431@krava>

On Wed, Dec 4, 2019 at 9:08 AM Jiri Olsa <jolsa@redhat.com> wrote:
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index c89c6495983d..32a5db900f47 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -116,6 +116,7 @@
>  #define AUDIT_FANOTIFY         1331    /* Fanotify access decision */
>  #define AUDIT_TIME_INJOFFSET   1332    /* Timekeeping offset injected */
>  #define AUDIT_TIME_ADJNTPVAL   1333    /* NTP value adjustment */
> +#define AUDIT_BPF              1334    /* BPF subsystem */
>
>  #define AUDIT_AVC              1400    /* SE Linux avc denial or grant */
>  #define AUDIT_SELINUX_ERR      1401    /* Internal SE Linux Errors */
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index e3461ec59570..81f1a6308aa8 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -23,6 +23,7 @@
>  #include <linux/timekeeping.h>
>  #include <linux/ctype.h>
>  #include <linux/nospec.h>
> +#include <linux/audit.h>
>  #include <uapi/linux/btf.h>
>
>  #define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \
> @@ -1306,6 +1307,33 @@ static int find_prog_type(enum bpf_prog_type type, struct bpf_prog *prog)
>         return 0;
>  }
>
> +enum bpf_audit {
> +       BPF_AUDIT_LOAD,
> +       BPF_AUDIT_UNLOAD,
> +};
> +
> +static const char * const bpf_audit_str[] = {
> +       [BPF_AUDIT_LOAD]   = "LOAD",
> +       [BPF_AUDIT_UNLOAD] = "UNLOAD",
> +};
> +
> +static void bpf_audit_prog(const struct bpf_prog *prog, enum bpf_audit op)
> +{
> +       struct audit_context *ctx = NULL;
> +       struct audit_buffer *ab;
> +
> +       if (audit_enabled == AUDIT_OFF)
> +               return;
> +       if (op == BPF_AUDIT_LOAD)
> +               ctx = audit_context();
> +       ab = audit_log_start(ctx, GFP_ATOMIC, AUDIT_BPF);
> +       if (unlikely(!ab))
> +               return;
> +       audit_log_format(ab, "prog-id=%u op=%s",
> +                        prog->aux->id, bpf_audit_str[op]);
> +       audit_log_end(ab);
> +}

As mentioned previously, I still think it might be a good idea to
ensure "op" is within the bounds of bpf_audit_str, but the audit bits
look reasonable to me.

>  int __bpf_prog_charge(struct user_struct *user, u32 pages)
>  {
>         unsigned long memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> @@ -1421,6 +1449,7 @@ static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock)
>  {
>         if (atomic64_dec_and_test(&prog->aux->refcnt)) {
>                 perf_event_bpf_event(prog, PERF_BPF_EVENT_PROG_UNLOAD, 0);
> +               bpf_audit_prog(prog, BPF_AUDIT_UNLOAD);
>                 /* bpf_prog_free_id() must be called first */
>                 bpf_prog_free_id(prog, do_idr_lock);
>                 __bpf_prog_put_noref(prog, true);
> @@ -1830,6 +1859,7 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
>          */
>         bpf_prog_kallsyms_add(prog);
>         perf_event_bpf_event(prog, PERF_BPF_EVENT_PROG_LOAD, 0);
> +       bpf_audit_prog(prog, BPF_AUDIT_LOAD);
>
>         err = bpf_prog_new_fd(prog);
>         if (err < 0)
> --
> 2.23.0

-- 
paul moore
www.paul-moore.com