bpf: Emit audit messages upon successful prog load and unload

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 20 12:45:51 2019
  type=PROCTITLE msg=audit(1574271951.590:8974): proctitle="./test_verifier"
  type=SYSCALL msg=audit(1574271951.590:8974): arch=c000003e syscall=321 success=yes exit=14 a0=5 a1=7ffe2d923e80 a2=78 a3=0 items=0 ppid=742 pid=949 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=2 comm="test_verifier" exe="/root/bpf-next/tools/testing/selftests/bpf/test_verifier" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
  type=UNKNOWN[1334] msg=audit(1574271951.590:8974): auid=0 uid=0 gid=0 ses=2 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 pid=949 comm="test_verifier" exe="/root/bpf-next/tools/testing/selftests/bpf/test_verifier" prog-id=3260 event=LOAD
  ----
  time->Wed Nov 20 12:45:51 2019
type=UNKNOWN[1334] msg=audit(1574271951.590:8975): prog-id=3260 event=UNLOAD
  ----
  [...]

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191120213816.8186-1-jolsa@kernel.org

diff --git a/include/linux/audit.h b/include/linux/audit.h
index aee3dc9eb378ec3ec69ea428975375a0758c1fb4..edd006f4597d4e79a15afee98784a278e6a09c93 100644 (file)
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -159,6 +159,7 @@ extern void             audit_log_key(struct audit_buffer *ab,
 extern void                audit_log_link_denied(const char *operation);
 extern void                audit_log_lost(const char *message);
 
+extern void audit_log_task(struct audit_buffer *ab);
 extern int audit_log_task_context(struct audit_buffer *ab);
 extern void audit_log_task_info(struct audit_buffer *ab);
 
@@ -219,6 +220,8 @@ static inline void audit_log_key(struct audit_buffer *ab, char *key)
 { }
 static inline void audit_log_link_denied(const char *string)
 { }
+static inline void audit_log_task(struct audit_buffer *ab)
+{ }
 static inline int audit_log_task_context(struct audit_buffer *ab)
 {
        return 0;

diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index c89c6495983d5d9d0f861ea180b8257aca96a453..32a5db900f4743fec550d90b12c7909d4ed4cebe 100644 (file)
--- 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/auditsc.c b/kernel/auditsc.c
index 4effe01ebbe2b3ad1e0d5cf566909db533dcb610..9bf1045fedfab20d2e19bea18825f2445d69132c 100644 (file)
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2545,7 +2545,7 @@ void __audit_ntp_log(const struct audit_ntp_data *ad)
        audit_log_ntp_val(ad, "adjust", AUDIT_NTP_ADJUST);
 }
 
-static void audit_log_task(struct audit_buffer *ab)
+void audit_log_task(struct audit_buffer *ab)
 {
        kuid_t auid, uid;
        kgid_t gid;

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index bac3becf9f90403b9ffff338889521af0be6f8bb..17f4254495f240613572acc5acbc2fe72bf4182e 100644 (file)
--- 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_PROG_ARRAY || \
@@ -1318,6 +1319,34 @@ static void free_used_maps(struct bpf_prog_aux *aux)
        kfree(aux->used_maps);
 }
 
+enum bpf_event {
+       BPF_EVENT_LOAD,
+       BPF_EVENT_UNLOAD,
+};
+
+static const char * const bpf_event_audit_str[] = {
+       [BPF_EVENT_LOAD]   = "LOAD",
+       [BPF_EVENT_UNLOAD] = "UNLOAD",
+};
+
+static void bpf_audit_prog(const struct bpf_prog *prog, enum bpf_event event)
+{
+       bool has_task_context = event == BPF_EVENT_LOAD;
+       struct audit_buffer *ab;
+
+       if (audit_enabled == AUDIT_OFF)
+               return;
+       ab = audit_log_start(audit_context(), GFP_ATOMIC, AUDIT_BPF);
+       if (unlikely(!ab))
+               return;
+       if (has_task_context)
+               audit_log_task(ab);
+       audit_log_format(ab, "%sprog-id=%u event=%s",
+                        has_task_context ? " " : "",
+                        prog->aux->id, bpf_event_audit_str[event]);
+       audit_log_end(ab);
+}
+
 int __bpf_prog_charge(struct user_struct *user, u32 pages)
 {
        unsigned long memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
@@ -1434,6 +1463,7 @@ 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_EVENT_UNLOAD);
                /* bpf_prog_free_id() must be called first */
                bpf_prog_free_id(prog, do_idr_lock);
                __bpf_prog_put_noref(prog, true);
@@ -1843,6 +1873,7 @@ 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_EVENT_LOAD);
 
        err = bpf_prog_new_fd(prog);
        if (err < 0)