[PATCH bpf-next v2 1/1] bpf: Include pid, uid and comm in audit output

[Dave Tucker <dave@xxxxxxxxxxxxx>]

Current output from auditd is as follows:

time->Wed Dec 13 21:39:24 2023
type=BPF msg=audit(1702503564.519:11241): prog-id=439 op=LOAD

This only tells you that a BPF program was loaded, but without
any context. If we include the prog-name, pid, uid and comm we get
output as follows:

time->Wed Dec 13 21:59:59 2023
type=BPF msg=audit(1702504799.156:99528): op=UNLOAD prog-id=50092
	prog-name="test" pid=27279 uid=0 comm="new_name"

With pid, uid a system administrator has much better context
over which processes and user loaded which eBPF programs.
comm is useful since processes may be short-lived.

Signed-off-by: Dave Tucker <dave@xxxxxxxxxxxxx>
---

Changes:

v1->v2:
  - Move 'op' to the front of the audit messages
  - Add 'prog-name' to the audit messages
  - Replace deprecated in_irq() with in_hardirq()
  - Remove in_irq() check from bpf_audit_prog since it's always called
    from the task context
  - Only populate pid, uid and comm if not in a kthread

 kernel/bpf/syscall.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 06320d9abf33..fbbaf3b8ad48 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -35,6 +35,7 @@
 #include <linux/rcupdate_trace.h>
 #include <linux/memcontrol.h>
 #include <linux/trace_events.h>
+#include <linux/uidgid.h>
 
 #include <net/netfilter/nf_bpf_link.h>
 #include <net/netkit.h>
@@ -2110,18 +2111,34 @@ static void bpf_audit_prog(const struct bpf_prog *prog, unsigned int op)
 {
 	struct audit_context *ctx = NULL;
 	struct audit_buffer *ab;
+	const struct cred *cred;
+	char comm[sizeof(current->comm)];
 
 	if (WARN_ON_ONCE(op >= BPF_AUDIT_MAX))
 		return;
 	if (audit_enabled == AUDIT_OFF)
 		return;
-	if (!in_irq() && !irqs_disabled())
-		ctx = audit_context();
+
+	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_format(ab, "op=%s prog-id=%u",
+			 bpf_audit_str[op], prog->aux->id);
+	audit_log_format(ab, " prog-name=");
+	audit_log_untrustedstring(ab, prog->aux->name ?: "(none)");
+
+	if (current->mm) {
+		cred = current_cred();
+		audit_log_format(ab, " pid=%u uid=%u",
+				 task_pid_nr(current),
+				 from_kuid(&init_user_ns, cred->uid));
+		audit_log_format(ab, " comm=");
+		audit_log_untrustedstring(ab, get_task_comm(comm, current));
+	} else {
+		audit_log_format(ab, " pid=? uid=? comm=?");
+	}
 	audit_log_end(ab);
 }
 
@@ -2212,7 +2229,7 @@ static void __bpf_prog_put(struct bpf_prog *prog)
 	struct bpf_prog_aux *aux = prog->aux;
 
 	if (atomic64_dec_and_test(&aux->refcnt)) {
-		if (in_irq() || irqs_disabled()) {
+		if (in_hardirq() || irqs_disabled()) {
 			INIT_WORK(&aux->work, bpf_prog_put_deferred);
 			schedule_work(&aux->work);
 		} else {
-- 
2.43.0