On Thu, Nov 28, 2019 at 4:16 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
> From: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
>
> Allow for audit messages to be emitted upon BPF program load and
> unload for having a timeline of events. The load itself is in
> syscall context, so additional info about the process initiating
> the BPF prog creation can be logged and later directly correlated
> to the unload event.
>
> The only info really needed from BPF side is the globally unique
> prog ID where then audit user space tooling can query / dump all
> info needed about the specific BPF program right upon load event
> and enrich the record, thus these changes needed here can be kept
> small and non-intrusive to the core.
>
> Raw example output:
>
> # auditctl -D
> # auditctl -a always,exit -F arch=x86_64 -S bpf
> # ausearch --start recent -m 1334
> ...
> ----
> time->Wed Nov 27 16:04:13 2019
> type=PROCTITLE msg=audit(1574867053.120:84664): proctitle="./bpf"
> type=SYSCALL msg=audit(1574867053.120:84664): arch=c000003e syscall=321 \
> success=yes exit=3 a0=5 a1=7ffea484fbe0 a2=70 a3=0 items=0 ppid=7477 \
> pid=12698 auid=1001 uid=1001 gid=1001 euid=1001 suid=1001 fsuid=1001 \
> egid=1001 sgid=1001 fsgid=1001 tty=pts2 ses=4 comm="bpf" \
> exe="/home/jolsa/auditd/audit-testsuite/tests/bpf/bpf" \
> subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
> type=UNKNOWN[1334] msg=audit(1574867053.120:84664): prog-id=76 op=LOAD
> ----
> time->Wed Nov 27 16:04:13 2019
> type=UNKNOWN[1334] msg=audit(1574867053.120:84665): prog-id=76 op=UNLOAD
> ...
>
> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Co-developed-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> include/uapi/linux/audit.h | 1 +
> kernel/bpf/syscall.c | 27 +++++++++++++++++++++++++++
> 2 files changed, 28 insertions(+)
Hi all, sorry for the delay; the merge window in combination with the
holiday in the US bumped this back a bit. Small comments inline below
...
> --- 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 +1307,30 @@ 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_buffer *ab;
> +
> + if (audit_enabled == AUDIT_OFF)
> + return;
I think you would probably also want to check the results of
audit_dummy_context() here as well, see all the various audit_XXX()
functions in include/linux/audit.h as an example. You'll see a
pattern similar to the following:
static inline void audit_foo(...)
{
if (unlikely(!audit_dummy_context()))
__audit_foo(...)
}
> + ab = audit_log_start(audit_context(), GFP_ATOMIC, AUDIT_BPF);
> + if (unlikely(!ab))
> + return;
> + audit_log_format(ab, "prog-id=%u op=%s",
> + prog->aux->id, bpf_audit_str[op]);
Is it worth putting some checks in here to make sure that you don't
blow past the end of the bpf_audit_str array?
> + audit_log_end(ab);
> +}
The audit record format looks much better now, thank you. Although I
do wonder if you want bpf_audit_prog() to live in kernel/bpf/syscall.c
or in kernel/auditsc.c? There is plenty of precedence for moving it
into auditsc.c and defining a no-op version for when
CONFIG_AUDITSYSCALL is not enabled, but I personally don't feel that
strongly about either option. I just wanted to mention this in case
you weren't already aware.
If you do keep it in syscall.c, I don't think there is a need to
implement a no-op version dependent on CONFIG_AUDITSYSCALL; that will
just clutter the code.
If you do move it to auditsc.c please change the name to
audit_bpf()/__audit_bpf() so it matches the other functions; if you
keep it in syscall.c you can name it whatever you like :)
--
paul moore
www.paul-moore.com
