netdev - [PATCH 10/10] tcp: handle shift/merge of cloned skbs too

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1227536527-29713-11-git-send-email-ilpo.jarvinen@helsinki.fi>
Date:	Mon, 24 Nov 2008 16:22:07 +0200
From:	"Ilpo JÃ¤rvinen" <ilpo.jarvinen@...sinki.fi>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org,
	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
Subject: [PATCH 10/10] tcp: handle shift/merge of cloned skbs too

This caused me to get repeatably:

  tcpdump: pcap_loop: recvfrom: Bad address

Happens occassionally when I tcpdump my for-looped test xfers:
  while [ : ]; do echo -n "$(date '+%s.%N') "; ./sendfile; sleep 20; done

Rest of the relevant commands:
  ethtool -K eth0 tso off
  tc qdisc add dev eth0 root netem drop 4%
  tcpdump -n -s0 -i eth0 -w sacklog.all

Running net-next under kvm, connection goes to the same host
(basically just out of kvm). The connection itself works ok
and data gets sent without corruption even with a large
number of tests while tcpdump fails usually within less than
5 tests.

Whether it only happens because of this change or not, I
don't know for sure but it's the only thing with which
I've seen that error. The non-cloned variant works w/o it
for much longer time. I'm yet to debug where the error
actually comes from.

Signed-off-by: Ilpo JÃ¤rvinen <ilpo.jarvinen@...sinki.fi>
---
 net/core/skbuff.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 844b8ab..57555a4 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2018,13 +2018,10 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len)
 		skb_split_no_header(skb, skb1, len, pos);
 }
 
-/* Shifting from/to a cloned skb is a no-go.
- *
- * TODO: handle cloned skbs by using pskb_expand_head()
- */
+/* Shifting from/to a cloned skb is a no-go. */
 static int skb_prepare_for_shift(struct sk_buff *skb)
 {
-	return skb_cloned(skb);
+	return skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
 }
 
 /**
-- 
1.5.2.2

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html