net/sched: cls_fw: Fix improper refcount update leads to use-after-free

In the event of a failure in tcf_change_indev(), fw_set_parms() will immediately return an error after incrementing or decrementing reference counter in tcf_bind_filter(). If attacker can control reference counter to zero and make reference freed, leading to use after free. In order to prevent this, move the point of possible failure above the point where the TC_FW_CLASSID is handled. Fixes: 1da177e ("Linux-2.6.12-rc2") Reported-by: M A Ramdhan <[email protected]> Signed-off-by: M A Ramdhan <[email protected]> Acked-by: Jamal Hadi Salim <[email protected]> Reviewed-by: Pedro Tammela <[email protected]> Message-ID: <[email protected]> Signed-off-by: Jakub Kicinski <[email protected]>
kawasaki · Jul 7, 2023 · 0323bce · 0323bce
1 parent 525c469
commit 0323bce
Showing 1 changed file with 5 additions and 5 deletions.
diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c
@@ -212,11 +212,6 @@ static int fw_set_parms(struct net *net, struct tcf_proto *tp,
 	if (err < 0)
 		return err;
 
-	if (tb[TCA_FW_CLASSID]) {
-		f->res.classid = nla_get_u32(tb[TCA_FW_CLASSID]);
-		tcf_bind_filter(tp, &f->res, base);
-	}
-
 	if (tb[TCA_FW_INDEV]) {
 		int ret;
 		ret = tcf_change_indev(net, tb[TCA_FW_INDEV], extack);
@@ -233,6 +228,11 @@ static int fw_set_parms(struct net *net, struct tcf_proto *tp,
 	} else if (head->mask != 0xFFFFFFFF)
 		return err;
 
+	if (tb[TCA_FW_CLASSID]) {
+		f->res.classid = nla_get_u32(tb[TCA_FW_CLASSID]);
+		tcf_bind_filter(tp, &f->res, base);
+	}
+
 	return 0;
 }