diff mbox series

[1/1] batman-adv: Don't skb_split skbuffs with frag_list

Message ID 20220508132110.20451-2-sw@simonwunderlich.de (mailing list archive)
State Not Applicable, archived
Delegated to: Simon Wunderlich
Headers
Series [1/1] batman-adv: Don't skb_split skbuffs with frag_list |

Commit Message

Simon Wunderlich May 8, 2022, 1:21 p.m. UTC 
  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(+)

Comments

patchwork-bot+netdevbpf@kernel.org May 10, 2022, 1:20 a.m. UTC | #1 
Hello:

This patch was applied to netdev/net.git (master)
by Simon Wunderlich <sw@simonwunderlich.de>:

On Sun,  8 May 2022 15:21:10 +0200 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [1/1] batman-adv: Don't skb_split skbuffs with frag_list
    https://git.kernel.org/netdev/net/c/a063f2fba3fa

You are awesome, thank you!
diff mbox series

Patch

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;