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From: Simon Wunderlich <sw@simonwunderlich.de>
To: davem@davemloft.net, kuba@kernel.org
Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org,
	Sven Eckelmann <sven@narfation.org>,
	Felix Kaechele <felix@kaechele.ca>,
	Simon Wunderlich <sw@simonwunderlich.de>
Subject: [PATCH 1/1] batman-adv: Don't skb_split skbuffs with frag_list
Date: Sun,  8 May 2022 15:21:10 +0200	[thread overview]
Message-ID: <20220508132110.20451-2-sw@simonwunderlich.de> (raw)
In-Reply-To: <20220508132110.20451-1-sw@simonwunderlich.de>

From: Sven Eckelmann <sven@narfation.org>

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>
 net/batman-adv/fragmentation.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/net/batman-adv/fragmentation.c b/net/batman-adv/fragmentation.c
index 0899a729a23f..c120c7c6d25f 100644
--- a/net/batman-adv/fragmentation.c
+++ b/net/batman-adv/fragmentation.c
@@ -475,6 +475,17 @@ int batadv_frag_send_packet(struct sk_buff *skb,
 		goto free_skb;
+	/* 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;

  reply	other threads:[~2022-05-08 13:21 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-08 13:21 [PATCH 0/1] pull request for net: batman-adv 2022-05-08 Simon Wunderlich
2022-05-08 13:21 ` Simon Wunderlich [this message]
2022-05-10  1:20   ` [PATCH 1/1] batman-adv: Don't skb_split skbuffs with frag_list patchwork-bot+netdevbpf

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