[PATCH] audit: avoid dropping live tree ref on fsnotify rule autoremove

[PATCH] audit: avoid dropping live tree ref on fsnotify rule autoremove

[Jérémy Jean]

audit_del_rule() is used for both netlink deletion templates and internal
fsnotify autoremove.  The former passes a parsed template which owns a
temporary tree reference; the latter passes the installed entry itself.

The unconditional audit_put_tree() at the end of audit_del_rule() assumes
the template case.  For mixed AUDIT_DIR plus AUDIT_EXE rules, an fsnotify
autoremove event therefore drops the installed rule's live tree reference.
Repeating this across rules sharing the same tree can free the tree while
another rule still references it, and a later autoremove dereferences the
freed pathname while comparing rules.

Move the temporary-tree put to audit_rule_change(), the caller that owns
deletion templates.  Keep it in the AUDIT_DEL_RULE cleanup so both
successful deletion and -ENOENT still release the parser-owned tree.

Fixes: 34d99af52ad4 ("audit: implement audit by executable")
Assisted-by: Codex:gpt-5
Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
---
 kernel/auditfilter.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 7f791afe5791..666c2091b9e4 100644
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -1023,7 +1023,6 @@ static inline int audit_add_rule(struct audit_entry *entry)
 int audit_del_rule(struct audit_entry *entry)
 {
 	struct audit_entry  *e;
-	struct audit_tree *tree = entry->rule.tree;
 	struct list_head *list;
 	int ret = 0;
 #ifdef CONFIG_AUDITSYSCALL
@@ -1071,9 +1070,6 @@ int audit_del_rule(struct audit_entry *entry)
 out:
 	mutex_unlock(&audit_filter_mutex);
 
-	if (tree)
-		audit_put_tree(tree);	/* that's the temporary one */
-
 	return ret;
 }
 
@@ -1158,6 +1154,8 @@ int audit_rule_change(int type, int seq, void *data, size_t datasz)
 	}
 
 	if (err || type == AUDIT_DEL_RULE) {
+		if (type == AUDIT_DEL_RULE && entry->rule.tree)
+			audit_put_tree(entry->rule.tree); /* that's the template one */
 		if (entry->rule.exe)
 			audit_remove_mark(entry->rule.exe);
 		audit_free_rule(entry);
-- 
2.47.3

Re: [PATCH] audit: avoid dropping live tree ref on fsnotify rule autoremove

[sashiko-bot]

> audit_del_rule() is used for both netlink deletion templates and internal
> fsnotify autoremove.  The former passes a parsed template which owns a
> temporary tree reference; the latter passes the installed entry itself.
> 
> The unconditional audit_put_tree() at the end of audit_del_rule() assumes
> the template case.  For mixed AUDIT_DIR plus AUDIT_EXE rules, an fsnotify
> autoremove event therefore drops the installed rule's live tree reference.
> Repeating this across rules sharing the same tree can free the tree while
> another rule still references it, and a later autoremove dereferences the
> freed pathname while comparing rules.
> 
> Move the temporary-tree put to audit_rule_change(), the caller that owns
> deletion templates.  Keep it in the AUDIT_DEL_RULE cleanup so both
> successful deletion and -ENOENT still release the parser-owned tree.
> 
> Fixes: 34d99af52ad4 ("audit: implement audit by executable")
> Assisted-by: Codex:gpt-5
> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260811220128.275783-1-Jeremy.Jean@oss.cyber.gouv.fr?part=1