diff mbox series

[SRU,Focal,v2,1/1] net/sched: cls_u32: Fix reference counter leak leading to overflow

Message ID 20230804201225.116222-2-yuxuan.luo@canonical.com
State New
Headers show
Series CVE-2023-3609 | expand

Commit Message

Yuxuan Luo Aug. 4, 2023, 8:12 p.m. UTC 
From: Lee Jones <lee@kernel.org>

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>
(cherry picked from commit 04c55383fa5689357bcdd2c8036725a55ed632bc)
CVE-2023-3609
Signed-off-by: Yuxuan Luo <yuxuan.luo@canonical.com>
---
 net/sched/cls_u32.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)
diff mbox series

Patch

diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index ed8d26e6468ca..e5cc2b4d38d5a 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -716,12 +716,18 @@  static int u32_set_parms(struct net *net, struct tcf_proto *tp,
 			 struct nlattr *est, bool ovr,
 			 struct netlink_ext_ack *extack)
 {
-	int err;
+	int err, ifindex = -1;
 
 	err = tcf_exts_validate(net, tp, tb, est, &n->exts, ovr, true, 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;
@@ -756,13 +762,9 @@  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;
 }