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57 lines
2.0 KiB
Diff
57 lines
2.0 KiB
Diff
From c7b18cdf1887e8ce91e04342cfd2d8fe1630be92 Mon Sep 17 00:00:00 2001
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From: Johannes Berg <johannes.berg@intel.com>
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Date: Sat, 1 Feb 2014 00:16:23 +0100
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Subject: mac80211: fix fragmentation code, particularly for encryption
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commit 338f977f4eb441e69bb9a46eaa0ac715c931a67f upstream.
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The "new" fragmentation code (since my rewrite almost 5 years ago)
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erroneously sets skb->len rather than using skb_trim() to adjust
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the length of the first fragment after copying out all the others.
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This leaves the skb tail pointer pointing to after where the data
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originally ended, and thus causes the encryption MIC to be written
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at that point, rather than where it belongs: immediately after the
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data.
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The impact of this is that if software encryption is done, then
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a) encryption doesn't work for the first fragment, the connection
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becomes unusable as the first fragment will never be properly
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verified at the receiver, the MIC is practically guaranteed to
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be wrong
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b) we leak up to 8 bytes of plaintext (!) of the packet out into
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the air
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This is only mitigated by the fact that many devices are capable
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of doing encryption in hardware, in which case this can't happen
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as the tail pointer is irrelevant in that case. Additionally,
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fragmentation is not used very frequently and would normally have
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to be configured manually.
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Fix this by using skb_trim() properly.
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Fixes: 2de8e0d999b8 ("mac80211: rewrite fragmentation")
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Reported-by: Jouni Malinen <j@w1.fi>
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Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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[bwh: Backported to 3.2: adjust context]
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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---
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net/mac80211/tx.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
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index 4ff35bf..5186f8b 100644
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--- a/net/mac80211/tx.c
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+++ b/net/mac80211/tx.c
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@@ -884,7 +884,7 @@ static int ieee80211_fragment(struct ieee80211_local *local,
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pos += fraglen;
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}
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- skb->len = hdrlen + per_fragm;
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+ skb_trim(skb, hdrlen + per_fragm);
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return 0;
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}
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--
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cgit v1.1
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