[PATCH v30 24/28] Audit: Add framework for auxiliary records

Casey Schaufler
2021-11-24T02:10:18Z

Add a list for auxiliary record data to the audit_buffer structure.
Add the audit_stamp information to the audit_buffer as there's no
guarantee that there will be an audit_context containing the stamp
associated with the event. At audit_log_end() time create auxiliary
records (none are currently defined) as have been added to the list.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
kernel/audit.c | 85 ++++++++++++++++++++++++++++++++++++++++++------
kernel/audit.h | 1 +
kernel/auditsc.c | 2 ++
3 files changed, 78 insertions(+), 10 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 069cd4c81a61..2b22498d3532 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -191,15 +191,25 @@ static struct audit_ctl_mutex {
* should be at least that large. */
#define AUDIT_BUFSIZ 1024

+/* The audit_context_entry contains data required to create an
+ * auxiliary record.
+ */
+struct audit_context_entry {
+ struct list_head list;
+ int type; /* Audit record type */
+};
+
/* The audit_buffer is used when formatting an audit record. The caller
* locks briefly to get the record off the freelist or to allocate the
* buffer, and locks briefly to send the buffer to the netlink layer or
* to place it on a transmit queue. Multiple audit_buffers can be in
* use simultaneously. */
struct audit_buffer {
- struct sk_buff *skb; /* formatted skb ready to send */
- struct audit_context *ctx; /* NULL or associated context */
- gfp_t gfp_mask;
+ struct sk_buff *skb; /* formatted skb ready to send */
+ struct audit_context *ctx; /* NULL or associated context */
+ struct list_head aux_records; /* aux record data */
+ struct audit_stamp stamp; /* event stamp */
+ gfp_t gfp_mask;
};

struct audit_reply {
@@ -1753,6 +1763,7 @@ static struct audit_buffer *audit_buffer_alloc(struct audit_context *ctx,

ab->ctx = ctx;
ab->gfp_mask = gfp_mask;
+ INIT_LIST_HEAD(&ab->aux_records);

return ab;

@@ -1813,7 +1824,6 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
int type)
{
struct audit_buffer *ab;
- struct audit_stamp stamp;

if (audit_initialized != AUDIT_INITIALIZED)
return NULL;
@@ -1866,14 +1876,14 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
return NULL;
}

- audit_get_stamp(ab->ctx, &stamp);
+ audit_get_stamp(ab->ctx, &ab->stamp);
/* cancel dummy context to enable supporting records */
if (ctx)
ctx->dummy = 0;
audit_log_format(ab, "audit(%llu.%03lu:%u): ",
- (unsigned long long)stamp.ctime.tv_sec,
- stamp.ctime.tv_nsec/1000000,
- stamp.serial);
+ (unsigned long long)ab->stamp.ctime.tv_sec,
+ ab->stamp.ctime.tv_nsec/1000000,
+ ab->stamp.serial);

return ab;
}
@@ -2363,7 +2373,7 @@ int audit_signal_info(int sig, struct task_struct *t)
}

/**
- * audit_log_end - end one audit record
+ * __audit_log_end - end one audit record
* @ab: the audit_buffer
*
* We can not do a netlink send inside an irq context because it blocks (last
@@ -2371,7 +2381,7 @@ int audit_signal_info(int sig, struct task_struct *t)
* queue and a kthread is scheduled to remove them from the queue outside the
* irq context. May be called in any context.
*/
-void audit_log_end(struct audit_buffer *ab)
+void __audit_log_end(struct audit_buffer *ab)
{
struct sk_buff *skb;
struct nlmsghdr *nlh;
@@ -2393,6 +2403,61 @@ void audit_log_end(struct audit_buffer *ab)
wake_up_interruptible(&kauditd_wait);
} else
audit_log_lost("rate limit exceeded");
+}
+
+/**
+ * audit_log_end - end one audit record
+ * @ab: the audit_buffer
+ *
+ * Let __audit_log_end() handle the message while the buffer housekeeping
+ * is done here.
+ * If there are other records that have been deferred for the event
+ * create them here.
+ */
+void audit_log_end(struct audit_buffer *ab)
+{
+ struct audit_context_entry *entry;
+ struct audit_context mcontext;
+ struct audit_context *mctx;
+ struct audit_buffer *mab;
+ struct list_head *l;
+ struct list_head *n;
+
+ if (!ab)
+ return;
+
+ __audit_log_end(ab);
+
+ if (list_empty(&ab->aux_records)) {
+ audit_buffer_free(ab);
+ return;
+ }
+
+ if (ab->ctx == NULL) {
+ mcontext.context = AUDIT_CTX_AUXRECORD;
+ mcontext.stamp = ab->stamp;
+ mctx = &mcontext;
+ } else
+ mctx = ab->ctx;
+
+ list_for_each_safe(l, n, &ab->aux_records) {
+ entry = list_entry(l, struct audit_context_entry, list);
+ mab = audit_log_start(mctx, ab->gfp_mask, entry->type);
+ if (!mab) {
+ audit_panic("alloc error in audit_log_end");
+ continue;
+ }
+ switch (entry->type) {
+ /* Don't know of any quite yet. */
+ default:
+ audit_panic("Unknown type in audit_log_end");
+ break;
+ }
+ __audit_log_end(mab);
+ audit_buffer_free(mab);
+ list_del(&entry->list);
+ kfree(entry);
+ }

audit_buffer_free(ab);
}
diff --git a/kernel/audit.h b/kernel/audit.h
index 56560846f3b0..f87da8e0a5a4 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -112,6 +112,7 @@ struct audit_context {
AUDIT_CTX_UNUSED, /* audit_context is currently unused */
AUDIT_CTX_SYSCALL, /* in use by syscall */
AUDIT_CTX_URING, /* in use by io_uring */
+ AUDIT_CTX_AUXRECORD, /* in use for auxiliary records */
} context;
enum audit_state state, current_state;
struct audit_stamp stamp; /* event identifier */
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index e6868d072648..c128f7e73e89 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1681,6 +1681,8 @@ static void audit_log_exit(void)
case AUDIT_CTX_URING:
audit_log_uring(context);
break;
+ case AUDIT_CTX_AUXRECORD:
+ break;
default:
BUG();
break;