From: M A Ramdhan Date: Wed, 5 Jul 2023 16:15:30 +0000 (-0400) Subject: net/sched: cls_fw: Fix improper refcount update leads to use-after-free X-Git-Tag: v4.14.322~28 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fa020e39526994c7248f241f75d615b0df5d7671;p=thirdparty%2Fkernel%2Fstable.git 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 --- diff --git a/net/sched/cls_fw.c b/net/sched/cls_fw.c index 7f45e5ab8afcd..e63f9c2e37e50 100644 --- a/net/sched/cls_fw.c +++ b/net/sched/cls_fw.c @@ -225,11 +225,6 @@ 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; @@ -248,6 +243,11 @@ 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; }