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Message-ID: <20241217230854.6588-3-casey@schaufler-ca.com>
Date: Tue, 17 Dec 2024 15:08:50 -0800
From: Casey Schaufler <casey@...aufler-ca.com>
To: casey@...aufler-ca.com,
paul@...l-moore.com,
eparis@...hat.com,
linux-security-module@...r.kernel.org,
audit@...r.kernel.org
Cc: jmorris@...ei.org,
serge@...lyn.com,
keescook@...omium.org,
john.johansen@...onical.com,
penguin-kernel@...ove.sakura.ne.jp,
stephen.smalley.work@...il.com,
linux-kernel@...r.kernel.org,
selinux@...r.kernel.org
Subject: [PATCH 2/6] Audit: Allow multiple records in an audit_buffer
Replace the single skb pointer in an audit_buffer with
a list of skb pointers. 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. Functions are created to manage the skb list
in the audit_buffer.
Suggested-by: Paul Moore <paul@...l-moore.com>
Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
---
kernel/audit.c | 111 +++++++++++++++++++++++++++++++++++++++----------
1 file changed, 89 insertions(+), 22 deletions(-)
diff --git a/kernel/audit.c b/kernel/audit.c
index 310c1a7859bb..e259c48d6148 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -195,8 +195,10 @@ static struct audit_ctl_mutex {
* 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 sk_buff *skb; /* the skb for audit_log functions */
+ struct sk_buff_head skb_list; /* formatted skbs, ready to send */
struct audit_context *ctx; /* NULL or associated context */
+ struct audit_stamp stamp; /* audit stamp for these records */
gfp_t gfp_mask;
};
@@ -1776,10 +1778,13 @@ __setup("audit_backlog_limit=", audit_backlog_limit_set);
static void audit_buffer_free(struct audit_buffer *ab)
{
+ struct sk_buff *skb;
+
if (!ab)
return;
- kfree_skb(ab->skb);
+ while ((skb = skb_dequeue(&ab->skb_list)))
+ kfree_skb(skb);
kmem_cache_free(audit_buffer_cache, ab);
}
@@ -1795,6 +1800,10 @@ static struct audit_buffer *audit_buffer_alloc(struct audit_context *ctx,
ab->skb = nlmsg_new(AUDIT_BUFSIZ, gfp_mask);
if (!ab->skb)
goto err;
+
+ skb_queue_head_init(&ab->skb_list);
+ skb_queue_tail(&ab->skb_list, ab->skb);
+
if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))
goto err;
@@ -1860,7 +1869,6 @@ 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;
@@ -1915,14 +1923,14 @@ 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;
}
@@ -2178,6 +2186,57 @@ void audit_log_key(struct audit_buffer *ab, char *key)
audit_log_format(ab, "(null)");
}
+/**
+ * audit_buffer_aux_new - Add an aux record buffer to the skb list
+ * @ab: audit_buffer
+ * @type: message type
+ *
+ * Aux records are allocated and added to the skb list of
+ * the "main" record. The ab->skb is reset to point to the
+ * aux record on its creation. When the aux record in complete
+ * ab->skb has to be reset to point to the "main" record.
+ * This allows the audit_log_ functions to be ignorant of
+ * which kind of record it is logging to. It also avoids adding
+ * special data for aux records.
+ *
+ * On success ab->skb will point to the new aux record.
+ * Returns 0 on success, -ENOMEM should allocation fail.
+ */
+static int audit_buffer_aux_new(struct audit_buffer *ab, int type)
+{
+ WARN_ON(ab->skb != skb_peek(&ab->skb_list));
+
+ ab->skb = nlmsg_new(AUDIT_BUFSIZ, ab->gfp_mask);
+ if (!ab->skb)
+ goto err;
+ if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))
+ goto err;
+ skb_queue_tail(&ab->skb_list, ab->skb);
+
+ audit_log_format(ab, "audit(%llu.%03lu:%u): ",
+ (unsigned long long)ab->stamp.ctime.tv_sec,
+ ab->stamp.ctime.tv_nsec/1000000,
+ ab->stamp.serial);
+
+ return 0;
+
+err:
+ kfree_skb(ab->skb);
+ ab->skb = skb_peek(&ab->skb_list);
+ return -ENOMEM;
+}
+
+/**
+ * audit_buffer_aux_end - Switch back to the "main" record from an aux record
+ * @ab: audit_buffer
+ *
+ * Restores the "main" audit record to ab->skb.
+ */
+static void audit_buffer_aux_end(struct audit_buffer *ab)
+{
+ ab->skb = skb_peek(&ab->skb_list);
+}
+
int audit_log_task_context(struct audit_buffer *ab)
{
struct lsm_prop prop;
@@ -2412,26 +2471,14 @@ int audit_signal_info(int sig, struct task_struct *t)
}
/**
- * 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
- * arg, flags, is not set to MSG_DONTWAIT), so the audit buffer is placed on a
- * queue and a kthread is scheduled to remove them from the queue outside the
- * irq context. May be called in any context.
+ * __audit_log_end - enqueue one audit record
+ * @skb: the buffer to send
*/
-void audit_log_end(struct audit_buffer *ab)
+static void __audit_log_end(struct sk_buff *skb)
{
- struct sk_buff *skb;
struct nlmsghdr *nlh;
- if (!ab)
- return;
-
if (audit_rate_check()) {
- skb = ab->skb;
- ab->skb = NULL;
-
/* setup the netlink header, see the comments in
* kauditd_send_multicast_skb() for length quirks */
nlh = nlmsg_hdr(skb);
@@ -2442,6 +2489,26 @@ 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
+ *
+ * We can not do a netlink send inside an irq context because it blocks (last
+ * arg, flags, is not set to MSG_DONTWAIT), so the audit buffer is placed on a
+ * 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)
+{
+ struct sk_buff *skb;
+
+ if (!ab)
+ return;
+
+ while ((skb = skb_dequeue(&ab->skb_list)))
+ __audit_log_end(skb);
audit_buffer_free(ab);
}
--
2.47.0
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