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

On Thu, Nov 28, 2019 at 4:16 AM Jiri Olsa <jolsa(a)kernel.org&gt; wrote: > From: Daniel Borkmann <daniel(a)iogearbox.net&gt; > > 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(a)iogearbox.net&gt; > Co-developed-by: Jiri Olsa <jolsa(a)kernel.org&gt; > Signed-off-by: Jiri Olsa <jolsa(a)kernel.org&gt; > --- > > 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