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batman-adv: Fix double free during fragment merge error

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commit 248e23b50e2da0753f3b5faa068939cbe9f8a75a upstream.

The function batadv_frag_skb_buffer was supposed not to consume the skbuff
on errors. This was followed in the helper function
batadv_frag_insert_packet when the skb would potentially be inserted in the
fragment queue. But it could happen that the next helper function
batadv_frag_merge_packets would try to merge the fragments and fail. This
results in a kfree_skb of all the enqueued fragments (including the just
inserted one). batadv_recv_frag_packet would detect the error in
batadv_frag_skb_buffer and try to free the skb again.

The behavior of batadv_frag_skb_buffer (and its helper
batadv_frag_insert_packet) must therefore be changed to always consume the
skbuff to have a common behavior and avoid the double kfree_skb.

Fixes: 610bfc6bc99b ("batman-adv: Receive fragmented packets and merge")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sven Eckelmann 2020-03-16 23:30:42 +01:00 committed by Greg Kroah-Hartman
parent af83aa2e1f
commit 351f7cbfff
2 changed files with 11 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
net/batman-adv/fragmentation.c
View File

@ -232,8 +232,10 @@ err_unlock:
spin_unlock_bh(&chain->lock);
err:
if (!ret)
if (!ret) {
kfree(frag_entry_new);
kfree_skb(skb);
}
return ret;
}
@ -305,7 +307,7 @@ free:
*
* There are three possible outcomes: 1) Packet is merged: Return true and
* set *skb to merged packet; 2) Packet is buffered: Return true and set *skb
* to NULL; 3) Error: Return false and leave skb as is.
* to NULL; 3) Error: Return false and free skb.
*
* Return: true when packet is merged or buffered, false when skb is not not
* used.
@ -330,9 +332,9 @@ bool batadv_frag_skb_buffer(struct sk_buff **skb,
goto out_err;
out:
*skb = skb_out;
ret = true;
out_err:
*skb = skb_out;
return ret;
}

6
net/batman-adv/routing.c
View File

@ -1080,6 +1080,12 @@ int batadv_recv_frag_packet(struct sk_buff *skb,
batadv_inc_counter(bat_priv, BATADV_CNT_FRAG_RX);
batadv_add_counter(bat_priv, BATADV_CNT_FRAG_RX_BYTES, skb->len);
/* batadv_frag_skb_buffer will always consume the skb and
* the caller should therefore never try to free the
* skb after this point
*/
ret = NET_RX_SUCCESS;
/* Add fragment to buffer and merge if possible. */
if (!batadv_frag_skb_buffer(&skb, orig_node_src))
goto out;