[3.19.y-ckt stable] Patch "sched: cls_flow: fix panic on filter replace" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    sched: cls_flow: fix panic on filter replace

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt6.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From b2141c89fc610617dadd6b75b1c6e9d5374c9ad9 Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <daniel at iogearbox.net>
Date: Fri, 17 Jul 2015 22:38:45 +0200
Subject: sched: cls_flow: fix panic on filter replace

commit 32b2f4b196b37695fdb42b31afcbc15399d6ef91 upstream.

The following test case causes a NULL pointer dereference in cls_flow:

  tc filter add dev foo parent 1: handle 0x1 flow hash keys dst action ok
  tc filter replace dev foo parent 1: pref 49152 handle 0x1 \
            flow hash keys mark action drop

To be more precise, actually two different panics are fixed, the first
occurs because tcf_exts_init() is not called on the newly allocated
filter when we do a replace. And the second panic uncovered after that
happens since the arguments of list_replace_rcu() are swapped, the old
element needs to be the first argument and the new element the second.

Fixes: 70da9f0bf999 ("net: sched: cls_flow use RCU")
Signed-off-by: Daniel Borkmann <daniel at iogearbox.net>
Acked-by: John Fastabend <john.r.fastabend at intel.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/sched/cls_flow.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/sched/cls_flow.c b/net/sched/cls_flow.c
index 15d68f2..bca348a 100644
--- a/net/sched/cls_flow.c
+++ b/net/sched/cls_flow.c
@@ -419,6 +419,8 @@ static int flow_change(struct net *net, struct sk_buff *in_skb,
 	if (!fnew)
 		goto err2;

+	tcf_exts_init(&fnew->exts, TCA_FLOW_ACT, TCA_FLOW_POLICE);
+
 	fold = (struct flow_filter *)*arg;
 	if (fold) {
 		err = -EINVAL;
@@ -480,7 +482,6 @@ static int flow_change(struct net *net, struct sk_buff *in_skb,
 		fnew->mask  = ~0U;
 		fnew->tp = tp;
 		get_random_bytes(&fnew->hashrnd, 4);
-		tcf_exts_init(&fnew->exts, TCA_FLOW_ACT, TCA_FLOW_POLICE);
 	}

 	fnew->perturb_timer.function = flow_perturbation;
@@ -520,7 +521,7 @@ static int flow_change(struct net *net, struct sk_buff *in_skb,
 	if (*arg == 0)
 		list_add_tail_rcu(&fnew->list, &head->filters);
 	else
-		list_replace_rcu(&fnew->list, &fold->list);
+		list_replace_rcu(&fold->list, &fnew->list);

 	*arg = (unsigned long)fnew;

--
1.9.1