batman-adv/patches/0003-batman-adv-Fix-double-free-during-fragment-merge-err.patch

   1 From: Sven Eckelmann <sven@narfation.org>
   2 Date: Sun, 12 Feb 2017 11:26:33 +0100
   3 Subject: [PATCH] batman-adv: Fix double free during fragment merge error
   4
   5 The function batadv_frag_skb_buffer was supposed not to consume the skbuff
   6 on errors. This was followed in the helper function
   7 batadv_frag_insert_packet when the skb would potentially be inserted in the
   8 fragment queue. But it could happen that the next helper function
   9 batadv_frag_merge_packets would try to merge the fragments and fail. This
  10 results in a kfree_skb of all the enqueued fragments (including the just
  11 inserted one). batadv_recv_frag_packet would detect the error in
  12 batadv_frag_skb_buffer and try to free the skb again.
  13
  14 The behavior of batadv_frag_skb_buffer (and its helper
  15 batadv_frag_insert_packet) must therefore be changed to always consume the
  16 skbuff to have a common behavior and avoid the double kfree_skb.
  17
  18 Fixes: 9b3eab61754d ("batman-adv: Receive fragmented packets and merge")
  19 Signed-off-by: Sven Eckelmann <sven@narfation.org>
  20
  21 Origin: upstream, https://git.open-mesh.org/batman-adv.git/commit/e3bab02816097f860545d9ce9ae0808c69d7c92f
  22 ---
  23  net/batman-adv/fragmentation.c | 8 +++++---
  24  1 file changed, 5 insertions(+), 3 deletions(-)
  25
  26 diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
  27 index 0854ebd8..31e97e9a 100644
  28 --- a/net/batman-adv/fragmentation.c
  29 +++ b/net/batman-adv/fragmentation.c
  30 @@ -239,8 +239,10 @@ err_unlock:
  31         spin_unlock_bh(&chain->lock);
  32
  33  err:
  34 -       if (!ret)
  35 +       if (!ret) {
  36                 kfree(frag_entry_new);
  37 +               kfree_skb(skb);
  38 +       }
  39
  40         return ret;
  41  }
  42 @@ -313,7 +315,7 @@ free:
  43   *
  44   * There are three possible outcomes: 1) Packet is merged: Return true and
  45   * set *skb to merged packet; 2) Packet is buffered: Return true and set *skb
  46 - * to NULL; 3) Error: Return false and leave skb as is.
  47 + * to NULL; 3) Error: Return false and free skb.
  48   *
  49   * Return: true when packet is merged or buffered, false when skb is not not
  50   * used.
  51 @@ -338,9 +340,9 @@ bool batadv_frag_skb_buffer(struct sk_buff **skb,
  52                 goto out_err;
  53
  54  out:
  55 -       *skb = skb_out;
  56         ret = true;
  57  out_err:
  58 +       *skb = skb_out;
  59         return ret;
  60  }
  61