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[ovs-dev,06/15] datapath: fix skb_panic due to the incorrect actions attrlen

Message ID 1505152570-6143-6-git-send-email-gvrose8192@gmail.com
State Superseded
Headers show
Series [ovs-dev,01/15] acinclude: Check for SKB_GSO_UDP | expand

Commit Message

Gregory Rose Sept. 11, 2017, 5:56 p.m. UTC
Upstream commit:
    commit 494bea39f3201776cdfddc232705f54a0bd210c4
    Author: Liping Zhang <zlpnobody@gmail.com>
    Date:   Wed Aug 16 13:30:07 2017 +0800

    openvswitch: fix skb_panic due to the incorrect actions attrlen

    For sw_flow_actions, the actions_len only represents the kernel part's
    size, and when we dump the actions to the userspace, we will do the
    convertions, so it's true size may become bigger than the actions_len.

    But unfortunately, for OVS_PACKET_ATTR_ACTIONS, we use the actions_len
    to alloc the skbuff, so the user_skb's size may become insufficient and
    oops will happen like this:
      skbuff: skb_over_panic: text:ffffffff8148fabf len:1749 put:157 head:
      ffff881300f39000 data:ffff881300f39000 tail:0x6d5 end:0x6c0 dev:<NULL>
      ------------[ cut here ]------------
      kernel BUG at net/core/skbuff.c:129!
      Call Trace:
       [<ffffffff8148be82>] skb_put+0x43/0x44
       [<ffffffff8148fabf>] skb_zerocopy+0x6c/0x1f4
       [<ffffffffa0290d36>] queue_userspace_packet+0x3a3/0x448 [openvswitch]
       [<ffffffffa0292023>] ovs_dp_upcall+0x30/0x5c [openvswitch]
       [<ffffffffa028d435>] output_userspace+0x132/0x158 [openvswitch]
       [<ffffffffa01e6890>] ? ip6_rcv_finish+0x74/0x77 [ipv6]
       [<ffffffffa028e277>] do_execute_actions+0xcc1/0xdc8 [openvswitch]
       [<ffffffffa028e3f2>] ovs_execute_actions+0x74/0x106 [openvswitch]
       [<ffffffffa0292130>] ovs_dp_process_packet+0xe1/0xfd [openvswitch]
       [<ffffffffa0292b77>] ? key_extract+0x63c/0x8d5 [openvswitch]
       [<ffffffffa029848b>] ovs_vport_receive+0xa1/0xc3 [openvswitch]

    Also we can find that the actions_len is much little than the orig_len:
      crash> struct sw_flow_actions 0xffff8812f539d000
      struct sw_flow_actions {
        rcu = {
          next = 0xffff8812f5398800,
          func = 0xffffe3b00035db32
        orig_len = 1384,
        actions_len = 592,
        actions = 0xffff8812f539d01c

    So as a quick fix, use the orig_len instead of the actions_len to alloc
    the user_skb.

    Last, this oops happened on our system running a relative old kernel, but
    the same risk still exists on the mainline, since we use the wrong
    actions_len from the beginning.

    Fixes: ccea74457bbd ("openvswitch: include datapath actions with sampled-pac
    Cc: Neil McKee <neil.mckee@inmon.com>
    Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
    Acked-by: Pravin B Shelar <pshelar@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Fixes: 0e469d3b380c ("datapath: Include datapath actions with sampled-packet upcall to userspace.")
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
 datapath/actions.c  | 1 +
 datapath/datapath.c | 7 ++++---
 datapath/datapath.h | 2 ++
 3 files changed, 7 insertions(+), 3 deletions(-)
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diff --git a/datapath/actions.c b/datapath/actions.c
index 59d91b2..ad18c2c 100644
--- a/datapath/actions.c
+++ b/datapath/actions.c
@@ -1348,6 +1348,7 @@  int ovs_execute_actions(struct datapath *dp, struct sk_buff *skb,
 		goto out;
+	OVS_CB(skb)->acts_origlen = acts->orig_len;
 	err = do_execute_actions(dp, skb, key,
 				 acts->actions, acts->actions_len);
diff --git a/datapath/datapath.c b/datapath/datapath.c
index b565fc5..1780819 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -388,7 +388,7 @@  static int queue_gso_packets(struct datapath *dp, struct sk_buff *skb,
 static size_t upcall_msg_size(const struct dp_upcall_info *upcall_info,
-			      unsigned int hdrlen)
+			      unsigned int hdrlen, int actions_attrlen)
 	size_t size = NLMSG_ALIGN(sizeof(struct ovs_header))
 		+ nla_total_size(hdrlen) /* OVS_PACKET_ATTR_PACKET */
@@ -405,7 +405,7 @@  static size_t upcall_msg_size(const struct dp_upcall_info *upcall_info,
 	if (upcall_info->actions_len)
-		size += nla_total_size(upcall_info->actions_len);
+		size += nla_total_size(actions_attrlen);
 	if (upcall_info->mru)
@@ -472,7 +472,8 @@  static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 		hlen = skb->len;
-	len = upcall_msg_size(upcall_info, hlen - cutlen);
+	len = upcall_msg_size(upcall_info, hlen - cutlen,
+			      OVS_CB(skb)->acts_origlen);
 	user_skb = genlmsg_new(len, GFP_ATOMIC);
 	if (!user_skb) {
 		err = -ENOMEM;
diff --git a/datapath/datapath.h b/datapath/datapath.h
index f20deed..70ad0ac 100644
--- a/datapath/datapath.h
+++ b/datapath/datapath.h
@@ -100,11 +100,13 @@  struct datapath {
  * when a packet is received by OVS.
  * @mru: The maximum received fragement size; 0 if the packet is not
  * fragmented.
+ * @acts_origlen: The netlink size of the flow actions applied to this skb.
  * @cutlen: The number of bytes from the packet end to be removed.
 struct ovs_skb_cb {
 	struct vport		*input_vport;
 	u16			mru;
+	u16			acts_origlen;
 	u32			cutlen;
 #define OVS_CB(skb) ((struct ovs_skb_cb *)(skb)->cb)