Patch "net/sched: cls_u32: Fix reference counter leak leading to overflow" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net/sched: cls_u32: Fix reference counter leak leading to overflow

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-sched-cls_u32-fix-reference-counter-leak-leading.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e442758c225c4c898f53ee27189cb264ac3d45cc
Author: Lee Jones <lee@xxxxxxxxxx>
Date:   Thu Jun 8 08:29:03 2023 +0100

    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 <edumazet@xxxxxxxxxx>
    Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
    Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Acked-by: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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;
 }