From: M A Ramdhan ramdhan@starlabs.sg

[ Upstream commit 0323bce598eea038714f941ce2b22541c46d488f ]

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 ramdhan@starlabs.sg Signed-off-by: M A Ramdhan ramdhan@starlabs.sg Acked-by: Jamal Hadi Salim jhs@mojatatu.com Reviewed-by: Pedro Tammela pctammela@mojatatu.com Message-ID: 20230705161530.52003-1-ramdhan@starlabs.sg Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: SeongJae Park sj@kernel.org --- 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 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; }