From 2749749afa071f8a0e405605de9da615e771a7ce Mon Sep 17 00:00:00 2001 From: Jiawei Ye Date: Mon, 2 Sep 2024 08:47:26 +0000 Subject: [PATCH] smackfs: Use rcu_assign_pointer() to ensure safe assignment in smk_set_cipso In the `smk_set_cipso` function, the `skp->smk_netlabel.attr.mls.cat` field is directly assigned to a new value without using the appropriate RCU pointer assignment functions. According to RCU usage rules, this is illegal and can lead to unpredictable behavior, including data inconsistencies and impossible-to-diagnose memory corruption issues. This possible bug was identified using a static analysis tool developed by myself, specifically designed to detect RCU-related issues. To address this, the assignment is now done using rcu_assign_pointer(), which ensures that the pointer assignment is done safely, with the necessary memory barriers and synchronization. This change prevents potential RCU dereference issues by ensuring that the `cat` field is safely updated while still adhering to RCU's requirements. Fixes: 0817534ff9ea ("smackfs: Fix use-after-free in netlbl_catmap_walk()") Signed-off-by: Jiawei Ye Signed-off-by: Casey Schaufler --- security/smack/smackfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c index e22aad7604e8..5dd1e164f9b1 100644 --- a/security/smack/smackfs.c +++ b/security/smack/smackfs.c @@ -932,7 +932,7 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf, } if (rc >= 0) { old_cat = skp->smk_netlabel.attr.mls.cat; - skp->smk_netlabel.attr.mls.cat = ncats.attr.mls.cat; + rcu_assign_pointer(skp->smk_netlabel.attr.mls.cat, ncats.attr.mls.cat); skp->smk_netlabel.attr.mls.lvl = ncats.attr.mls.lvl; synchronize_rcu(); netlbl_catmap_free(old_cat);