[PATCH v3 3/8] audit: add filtering for io_uring records
Paul Moore
paul at paul-moore.com
Tue Sep 14 03:33:10 UTC 2021
This patch adds basic audit io_uring filtering, using as much of the
existing audit filtering infrastructure as possible. In order to do
this we reuse the audit filter rule's syscall mask for the io_uring
operation and we create a new filter for io_uring operations as
AUDIT_FILTER_URING_EXIT/audit_filter_list[7].
Thanks to Richard Guy Briggs for his review, feedback, and work on
the corresponding audit userspace changes.
Signed-off-by: Paul Moore <paul at paul-moore.com>
---
v3:
- removed work-in-progress warning from the description
v2:
- incorporate feedback from Richard
v1:
- initial draft
---
include/uapi/linux/audit.h | 3 +-
kernel/audit_tree.c | 3 +-
kernel/audit_watch.c | 3 +-
kernel/auditfilter.c | 15 +++++++++--
kernel/auditsc.c | 61 ++++++++++++++++++++++++++++++++++----------
5 files changed, 65 insertions(+), 20 deletions(-)
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index a1997697c8b1..ecf1edd2affa 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -167,8 +167,9 @@
#define AUDIT_FILTER_EXCLUDE 0x05 /* Apply rule before record creation */
#define AUDIT_FILTER_TYPE AUDIT_FILTER_EXCLUDE /* obsolete misleading naming */
#define AUDIT_FILTER_FS 0x06 /* Apply rule at __audit_inode_child */
+#define AUDIT_FILTER_URING_EXIT 0x07 /* Apply rule at io_uring op exit */
-#define AUDIT_NR_FILTERS 7
+#define AUDIT_NR_FILTERS 8
#define AUDIT_FILTER_PREPEND 0x10 /* Prepend to front of list */
diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
index 2cd7b5694422..338c53a961c5 100644
--- a/kernel/audit_tree.c
+++ b/kernel/audit_tree.c
@@ -726,7 +726,8 @@ int audit_make_tree(struct audit_krule *rule, char *pathname, u32 op)
{
if (pathname[0] != '/' ||
- rule->listnr != AUDIT_FILTER_EXIT ||
+ (rule->listnr != AUDIT_FILTER_EXIT &&
+ rule->listnr != AUDIT_FILTER_URING_EXIT) ||
op != Audit_equal ||
rule->inode_f || rule->watch || rule->tree)
return -EINVAL;
diff --git a/kernel/audit_watch.c b/kernel/audit_watch.c
index 2acf7ca49154..698b62b4a2ec 100644
--- a/kernel/audit_watch.c
+++ b/kernel/audit_watch.c
@@ -183,7 +183,8 @@ int audit_to_watch(struct audit_krule *krule, char *path, int len, u32 op)
return -EOPNOTSUPP;
if (path[0] != '/' || path[len-1] == '/' ||
- krule->listnr != AUDIT_FILTER_EXIT ||
+ (krule->listnr != AUDIT_FILTER_EXIT &&
+ krule->listnr != AUDIT_FILTER_URING_EXIT) ||
op != Audit_equal ||
krule->inode_f || krule->watch || krule->tree)
return -EINVAL;
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index db2c6b59dfc3..d75acb014ccd 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -44,7 +44,8 @@ struct list_head audit_filter_list[AUDIT_NR_FILTERS] = {
LIST_HEAD_INIT(audit_filter_list[4]),
LIST_HEAD_INIT(audit_filter_list[5]),
LIST_HEAD_INIT(audit_filter_list[6]),
-#if AUDIT_NR_FILTERS != 7
+ LIST_HEAD_INIT(audit_filter_list[7]),
+#if AUDIT_NR_FILTERS != 8
#error Fix audit_filter_list initialiser
#endif
};
@@ -56,6 +57,7 @@ static struct list_head audit_rules_list[AUDIT_NR_FILTERS] = {
LIST_HEAD_INIT(audit_rules_list[4]),
LIST_HEAD_INIT(audit_rules_list[5]),
LIST_HEAD_INIT(audit_rules_list[6]),
+ LIST_HEAD_INIT(audit_rules_list[7]),
};
DEFINE_MUTEX(audit_filter_mutex);
@@ -151,7 +153,8 @@ char *audit_unpack_string(void **bufp, size_t *remain, size_t len)
static inline int audit_to_inode(struct audit_krule *krule,
struct audit_field *f)
{
- if (krule->listnr != AUDIT_FILTER_EXIT ||
+ if ((krule->listnr != AUDIT_FILTER_EXIT &&
+ krule->listnr != AUDIT_FILTER_URING_EXIT) ||
krule->inode_f || krule->watch || krule->tree ||
(f->op != Audit_equal && f->op != Audit_not_equal))
return -EINVAL;
@@ -248,6 +251,7 @@ static inline struct audit_entry *audit_to_entry_common(struct audit_rule_data *
pr_err("AUDIT_FILTER_ENTRY is deprecated\n");
goto exit_err;
case AUDIT_FILTER_EXIT:
+ case AUDIT_FILTER_URING_EXIT:
case AUDIT_FILTER_TASK:
#endif
case AUDIT_FILTER_USER:
@@ -332,6 +336,10 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
if (entry->rule.listnr != AUDIT_FILTER_FS)
return -EINVAL;
break;
+ case AUDIT_PERM:
+ if (entry->rule.listnr == AUDIT_FILTER_URING_EXIT)
+ return -EINVAL;
+ break;
}
switch (entry->rule.listnr) {
@@ -980,7 +988,8 @@ static inline int audit_add_rule(struct audit_entry *entry)
}
entry->rule.prio = ~0ULL;
- if (entry->rule.listnr == AUDIT_FILTER_EXIT) {
+ if (entry->rule.listnr == AUDIT_FILTER_EXIT ||
+ entry->rule.listnr == AUDIT_FILTER_URING_EXIT) {
if (entry->rule.flags & AUDIT_FILTER_PREPEND)
entry->rule.prio = ++prio_high;
else
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 62fb502da3fc..3cbcc999aff6 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -805,6 +805,35 @@ static int audit_in_mask(const struct audit_krule *rule, unsigned long val)
return rule->mask[word] & bit;
}
+/**
+ * audit_filter_uring - apply filters to an io_uring operation
+ * @tsk: associated task
+ * @ctx: audit context
+ */
+static void audit_filter_uring(struct task_struct *tsk,
+ struct audit_context *ctx)
+{
+ struct audit_entry *e;
+ enum audit_state state;
+
+ if (auditd_test_task(tsk))
+ return;
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_URING_EXIT],
+ list) {
+ if (audit_in_mask(&e->rule, ctx->uring_op) &&
+ audit_filter_rules(tsk, &e->rule, ctx, NULL, &state,
+ false)) {
+ rcu_read_unlock();
+ ctx->current_state = state;
+ return;
+ }
+ }
+ rcu_read_unlock();
+ return;
+}
+
/* At syscall exit time, this filter is called if the audit_state is
* not low enough that auditing cannot take place, but is also not
* high enough that we already know we have to write an audit record
@@ -1765,7 +1794,7 @@ static void audit_log_exit(void)
* __audit_free - free a per-task audit context
* @tsk: task whose audit context block to free
*
- * Called from copy_process and do_exit
+ * Called from copy_process, do_exit, and the io_uring code
*/
void __audit_free(struct task_struct *tsk)
{
@@ -1783,15 +1812,21 @@ void __audit_free(struct task_struct *tsk)
* random task_struct that doesn't doesn't have any meaningful data we
* need to log via audit_log_exit().
*/
- if (tsk == current && !context->dummy &&
- context->context == AUDIT_CTX_SYSCALL) {
+ if (tsk == current && !context->dummy) {
context->return_valid = AUDITSC_INVALID;
context->return_code = 0;
-
- audit_filter_syscall(tsk, context);
- audit_filter_inodes(tsk, context);
- if (context->current_state == AUDIT_STATE_RECORD)
- audit_log_exit();
+ if (context->context == AUDIT_CTX_SYSCALL) {
+ audit_filter_syscall(tsk, context);
+ audit_filter_inodes(tsk, context);
+ if (context->current_state == AUDIT_STATE_RECORD)
+ audit_log_exit();
+ } else if (context->context == AUDIT_CTX_URING) {
+ /* TODO: verify this case is real and valid */
+ audit_filter_uring(tsk, context);
+ audit_filter_inodes(tsk, context);
+ if (context->current_state == AUDIT_STATE_RECORD)
+ audit_log_uring(context);
+ }
}
audit_set_context(tsk, NULL);
@@ -1875,12 +1910,6 @@ void __audit_uring_exit(int success, long code)
{
struct audit_context *ctx = audit_context();
- /*
- * TODO: At some point we will likely want to filter on io_uring ops
- * and other things similar to what we do for syscalls, but that
- * is something for another day; just record what we can here.
- */
-
if (ctx->context == AUDIT_CTX_SYSCALL) {
/*
* NOTE: See the note in __audit_uring_entry() about the case
@@ -1903,6 +1932,8 @@ void __audit_uring_exit(int success, long code)
* the behavior here.
*/
audit_filter_syscall(current, ctx);
+ if (ctx->current_state != AUDIT_STATE_RECORD)
+ audit_filter_uring(current, ctx);
audit_filter_inodes(current, ctx);
if (ctx->current_state != AUDIT_STATE_RECORD)
return;
@@ -1915,6 +1946,8 @@ void __audit_uring_exit(int success, long code)
if (!list_empty(&ctx->killed_trees))
audit_kill_trees(ctx);
+ /* run through both filters to ensure we set the filterkey properly */
+ audit_filter_uring(current, ctx);
audit_filter_inodes(current, ctx);
if (ctx->current_state != AUDIT_STATE_RECORD)
goto out;
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