From aa650d87a498844060eecb1d336f4d46f4d1b0b3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= Date: Tue, 22 Sep 2026 20:27:35 +0000 Subject: [PATCH] audit: fix exe mark UAF in kill_rules() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit kill_rules() removes mixed AUDIT_DIR and AUDIT_EXE rules when an audit tree is pruned. It drops entry->rule.exe before removing the rule from the RCU-visible filter lists. After a rule has been installed with AUDIT_ADD_RULE, which requires CAP_AUDIT_CONTROL, removing the watched directory can race with another task that is still evaluating the rule. In that case, fsnotify can free the executable mark before the reader reaches audit_mark_compare(), causing a use-after-free. KASAN reports: BUG: KASAN: slab-use-after-free in audit_mark_compare+0x8d/0xa0 Unlink the published rules from the RCU-visible lists and retain them on tree->rules for cleanup. If any rule has an executable mark, wait for a single RCU grace period before removing the marks and scheduling the entries for freeing. Otherwise, call_rcu() already provides the required deferred freeing without a synchronous wait. Cc: stable@vger.kernel.org Fixes: 34d99af52ad4 ("audit: implement audit by executable") Assisted-by: Codex:gpt-5 Signed-off-by: Jérémy Jean Reviewed-by: Ricardo Robaina Tested-by: Ricardo Robaina Reviewed-by: Bradley Morgan Signed-off-by: Paul Moore --- kernel/audit_tree.c | 36 ++++++++++++++++++++++++++---------- 1 file changed, 26 insertions(+), 10 deletions(-) diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c index 1ed19b775912..f2e81be8265e 100644 --- a/kernel/audit_tree.c +++ b/kernel/audit_tree.c @@ -545,21 +545,37 @@ static void kill_rules(struct audit_context *context, struct audit_tree *tree) { struct audit_krule *rule, *next; struct audit_entry *entry; + bool need_sync = false; + + list_for_each_entry_safe(rule, next, &tree->rules, rlist) { + entry = container_of(rule, struct audit_entry, rule); + + if (rule->tree) { + /* not a half-baked one */ + audit_tree_log_remove_rule(context, rule); + rule->tree = NULL; + list_del_rcu(&entry->list); + list_del(&entry->rule.list); + if (entry->rule.exe) + need_sync = true; + } else { + list_del_init(&rule->rlist); + } + } + + if (list_empty(&tree->rules)) + return; + + if (need_sync) + synchronize_rcu(); list_for_each_entry_safe(rule, next, &tree->rules, rlist) { entry = container_of(rule, struct audit_entry, rule); list_del_init(&rule->rlist); - if (rule->tree) { - /* not a half-baked one */ - audit_tree_log_remove_rule(context, rule); - if (entry->rule.exe) - audit_remove_mark(entry->rule.exe); - rule->tree = NULL; - list_del_rcu(&entry->list); - list_del(&entry->rule.list); - call_rcu(&entry->rcu, audit_free_rule_rcu); - } + if (entry->rule.exe) + audit_remove_mark(entry->rule.exe); + call_rcu(&entry->rcu, audit_free_rule_rcu); } }