From 07f9cc229b44cbcee6385802d390091d915f38c3 Mon Sep 17 00:00:00 2001 From: Lee Jones Date: Thu, 8 Jun 2023 08:29:03 +0100 Subject: [PATCH] net/sched: cls_u32: Fix reference counter leak leading to overflow [ Upstream commit 04c55383fa5689357bcdd2c8036725a55ed632bc ] In the event of a failure in tcf_change_indev(), u32_set_parms() will immediately return without decrementing the recently incremented reference counter. If this happens enough times, the counter will rollover and the reference freed, leading to a double free which can be used to do 'bad things'. In order to prevent this, move the point of possible failure above the point where the reference counter is incremented. Also save any meaningful return values to be applied to the return data at the appropriate point in time. This issue was caught with KASAN. Fixes: 705c7091262d ("net: sched: cls_u32: no need to call tcf_exts_change for newly allocated struct") Suggested-by: Eric Dumazet Signed-off-by: Lee Jones Reviewed-by: Eric Dumazet Acked-by: Jamal Hadi Salim Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/sched/cls_u32.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index 34d25f7a0687..a3477537c102 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -716,13 +716,19 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp, struct nlattr *est, u32 flags, u32 fl_flags, struct netlink_ext_ack *extack) { - int err; + int err, ifindex = -1; err = tcf_exts_validate_ex(net, tp, tb, est, &n->exts, flags, fl_flags, extack); if (err < 0) return err; + if (tb[TCA_U32_INDEV]) { + ifindex = tcf_change_indev(net, tb[TCA_U32_INDEV], extack); + if (ifindex < 0) + return -EINVAL; + } + if (tb[TCA_U32_LINK]) { u32 handle = nla_get_u32(tb[TCA_U32_LINK]); struct tc_u_hnode *ht_down = NULL, *ht_old; @@ -757,13 +763,9 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp, tcf_bind_filter(tp, &n->res, base); } - if (tb[TCA_U32_INDEV]) { - int ret; - ret = tcf_change_indev(net, tb[TCA_U32_INDEV], extack); - if (ret < 0) - return -EINVAL; - n->ifindex = ret; - } + if (ifindex >= 0) + n->ifindex = ifindex; + return 0; }