From 612f468cfc3df83777ae21058419b1fc8e9037eb Mon Sep 17 00:00:00 2001 From: M A Ramdhan Date: Wed, 5 Jul 2023 12:15:30 -0400 Subject: [PATCH] net/sched: cls_fw: Fix improper refcount update leads to use-after-free commit 0323bce598eea038714f941ce2b22541c46d488f upstream. 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: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: M A Ramdhan Signed-off-by: M A Ramdhan Acked-by: Jamal Hadi Salim Reviewed-by: Pedro Tammela Message-ID: <20230705161530.52003-1-ramdhan@starlabs.sg> Signed-off-by: Jakub Kicinski Signed-off-by: SeongJae Park Signed-off-by: Greg Kroah-Hartman --- net/sched/cls_fw.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c index cb2c62605fc7..5284a473c697 100644 --- a/net/sched/cls_fw.c +++ b/net/sched/cls_fw.c @@ -221,11 +221,6 @@ 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); - } - #ifdef CONFIG_NET_CLS_IND if (tb[TCA_FW_INDEV]) { int ret; @@ -244,6 +239,11 @@ 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; }