The following commit has been merged in the batadv/lts/4.9 branch: commit 46673bf613ee683a987996bb8ac19b46a9a972f0 Author: Sven Eckelmann sven@narfation.org Date: Sat Apr 16 13:51:10 2022 +0200

batman-adv: Don't skb_split skbuffs with frag_list

commit a063f2fba3fa633a599253b62561051ac185fa99 upstream.

The receiving interface might have used GRO to receive more fragments than MAX_SKB_FRAGS fragments. In this case, these will not be stored in skb_shinfo(skb)->frags but merged into the frag list.

batman-adv relies on the function skb_split to split packets up into multiple smaller packets which are not larger than the MTU on the outgoing interface. But this function cannot handle frag_list entries and is only operating on skb_shinfo(skb)->frags. If it is still trying to split such an skb and xmit'ing it on an interface without support for NETIF_F_FRAGLIST, then validate_xmit_skb() will try to linearize it. But this fails due to inconsistent information. And __pskb_pull_tail will trigger a BUG_ON after skb_copy_bits() returns an error.

In case of entries in frag_list, just linearize the skb before operating on it with skb_split().

Reported-by: Felix Kaechele felix@kaechele.ca Fixes: c6c8fea29769 ("net: Add batman-adv meshing protocol") Signed-off-by: Sven Eckelmann sven@narfation.org Tested-by: Felix Kaechele felix@kaechele.ca Signed-off-by: Simon Wunderlich sw@simonwunderlich.de

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c index 343f4fc5909d..0b882f805c2f 100644 --- a/net/batman-adv/fragmentation.c +++ b/net/batman-adv/fragmentation.c @@ -478,6 +478,17 @@ int batadv_frag_send_packet(struct sk_buff *skb, if (!primary_if) goto out;

+ /* GRO might have added fragments to the fragment list instead of + * frags[]. But this is not handled by skb_split and must be + * linearized to avoid incorrect length information after all + * batman-adv fragments were created and submitted to the + * hard-interface + */ + if (skb_has_frag_list(skb) && __skb_linearize(skb)) { + ret = -ENOMEM; + goto free_skb; + } + /* Create one header to be copied to all fragments */ frag_header.packet_type = BATADV_UNICAST_FRAG; frag_header.version = BATADV_COMPAT_VERSION;