From: Lee Jones <lee@kernel.org>
Date: Thu, 8 Jun 2023 08:29:03 +0100
Subject: net/sched: cls_u32: Fix reference counter leak leading to overflow
Patch-mainline: v6.4-rc7
Git-commit: 04c55383fa5689357bcdd2c8036725a55ed632bc
References: CVE-2023-3609 bsc#1213586
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 <edumazet@google.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>
---
net/sched/cls_u32.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -729,11 +729,22 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
struct netlink_ext_ack *extack)
{
int err;
+#ifdef CONFIG_NET_CLS_IND
+ int ifindex = -1;
+#endif
err = tcf_exts_validate(net, tp, tb, est, &n->exts, ovr, extack);
if (err < 0)
return err;
+#ifdef CONFIG_NET_CLS_IND
+ if (tb[TCA_U32_INDEV]) {
+ ifindex = tcf_change_indev(net, tb[TCA_U32_INDEV], extack);
+ if (ifindex < 0)
+ return -EINVAL;
+ }
+#endif
+
if (tb[TCA_U32_LINK]) {
u32 handle = nla_get_u32(tb[TCA_U32_LINK]);
struct tc_u_hnode *ht_down = NULL, *ht_old;
@@ -769,13 +780,8 @@ static int u32_set_parms(struct net *net, struct tcf_proto *tp,
}
#ifdef CONFIG_NET_CLS_IND
- 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;
#endif
return 0;
}