This is a note to let you know that I've just added the patch titled
mac80211: fix fragmentation code, particularly for encryption
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mac80211-fix-fragmentation-code-particularly-for-encryption.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 338f977f4eb441e69bb9a46eaa0ac715c931a67f Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg@xxxxxxxxx>
Date: Sat, 1 Feb 2014 00:16:23 +0100
Subject: mac80211: fix fragmentation code, particularly for encryption
From: Johannes Berg <johannes.berg@xxxxxxxxx>
commit 338f977f4eb441e69bb9a46eaa0ac715c931a67f upstream.
The "new" fragmentation code (since my rewrite almost 5 years ago)
erroneously sets skb->len rather than using skb_trim() to adjust
the length of the first fragment after copying out all the others.
This leaves the skb tail pointer pointing to after where the data
originally ended, and thus causes the encryption MIC to be written
at that point, rather than where it belongs: immediately after the
data.
The impact of this is that if software encryption is done, then
a) encryption doesn't work for the first fragment, the connection
becomes unusable as the first fragment will never be properly
verified at the receiver, the MIC is practically guaranteed to
be wrong
b) we leak up to 8 bytes of plaintext (!) of the packet out into
the air
This is only mitigated by the fact that many devices are capable
of doing encryption in hardware, in which case this can't happen
as the tail pointer is irrelevant in that case. Additionally,
fragmentation is not used very frequently and would normally have
to be configured manually.
Fix this by using skb_trim() properly.
Fixes: 2de8e0d999b8 ("mac80211: rewrite fragmentation")
Reported-by: Jouni Malinen <j@xxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/mac80211/tx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -907,7 +907,7 @@ static int ieee80211_fragment(struct iee
}
/* adjust first fragment's length */
- skb->len = hdrlen + per_fragm;
+ skb_trim(skb, hdrlen + per_fragm);
return 0;
}
Patches currently in stable-queue which might be from johannes.berg@xxxxxxxxx are
queue-3.4/mac80211-fix-fragmentation-code-particularly-for-encryption.patch
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