[PATCH 1/1] audit: fix potential use-after-free in audit_del_rule()

From: Luxiao Xu <[email protected]>

`audit_del_rule()` destroys `e->rule.exe` via `audit_remove_mark_rule()`
before unlinking the rule from RCU-visible filter lists and waiting for a
grace period. Concurrent readers in `audit_filter()` and
`audit_filter_rules()` still dereference `e->rule.exe`, while the fsnotify
mark can be freed on an independent lifetime path. This creates a use-after-free
window during rule deletion.

Fix this by unlinking the rule from the RCU-visible lists and invoking
`synchronize_rcu()` before calling `audit_remove_mark_rule()` (and other
rule removal helpers). This ensures that all existing RCU readers have exited
the critical section before any underlying resources are destroyed.

Fixes: 34d99af52ad4 ("audit: implement audit by executable")
Cc: [email protected]
Reported-by: Vega <[email protected]>
Assisted-by: Codex:gpt-5.4
Signed-off-by: Luxiao Xu <[email protected]>
Signed-off-by: Ren Wei <[email protected]>
---
 kernel/auditfilter.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 4401119b5275..7f791afe5791 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -1045,6 +1045,10 @@ int audit_del_rule(struct audit_entry *entry)
 		goto out;
 	}
 
+	list_del_rcu(&e->list);
+	list_del(&e->rule.list);
+	synchronize_rcu();
+
 	if (e->rule.watch)
 		audit_remove_watch_rule(&e->rule);
 
@@ -1062,8 +1066,6 @@ int audit_del_rule(struct audit_entry *entry)
 		audit_signals--;
 #endif
 
-	list_del_rcu(&e->list);
-	list_del(&e->rule.list);
 	call_rcu(&e->rcu, audit_free_rule_rcu);
 
 out:
-- 
2.43.0