[PATCH 4.9 042/102] net_sched: keep alloc_hash updated after hash allocation

[Greg Kroah-Hartman]

From: Cong Wang <xiyou.wangcong@xxxxxxxxx>

[ Upstream commit 0d1c3530e1bd38382edef72591b78e877e0edcd3 ]

In commit 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex")
I moved cp->hash calculation before the first
tcindex_alloc_perfect_hash(), but cp->alloc_hash is left untouched.
This difference could lead to another out of bound access.

cp->alloc_hash should always be the size allocated, we should
update it after this tcindex_alloc_perfect_hash().

Reported-and-tested-by: syzbot+dcc34d54d68ef7d2d53d@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-and-tested-by: syzbot+c72da7b9ed57cde6fca2@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 599be01ee567 ("net_sched: fix an OOB access in cls_tcindex")
Cc: Jamal Hadi Salim <jhs@xxxxxxxxxxxx>
Cc: Jiri Pirko <jiri@xxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/sched/cls_tcindex.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/sched/cls_tcindex.c
+++ b/net/sched/cls_tcindex.c
@@ -325,6 +325,7 @@ tcindex_set_parms(struct net *net, struc
 
 		if (tcindex_alloc_perfect_hash(cp) < 0)
 			goto errout;
+		cp->alloc_hash = cp->hash;
 		for (i = 0; i < min(cp->hash, p->hash); i++)
 			cp->perfect[i].res = p->perfect[i].res;
 		balloc = 1;