50 lines
1.8 KiB
Diff
50 lines
1.8 KiB
Diff
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From: Johannes Berg <johannes.berg@intel.com>
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Date: Tue, 9 Nov 2021 10:02:04 +0100
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Subject: [PATCH] mac80211: fix radiotap header generation
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In commit 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header
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bitmap") we accidentally pointed the position to the wrong place, so
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we overwrite a present bitmap, and thus cause all kinds of trouble.
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To see the issue, note that the previous code read:
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pos = (void *)(it_present + 1);
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The requirement now is that we need to calculate pos via it_optional,
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to not trigger the compiler hardening checks, as:
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pos = (void *)&rthdr->it_optional[...];
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Rewriting the original expression, we get (obviously, since that just
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adds "+ x - x" terms):
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pos = (void *)(it_present + 1 + rthdr->it_optional - rthdr->it_optional)
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and moving the "+ rthdr->it_optional" outside to be used as an array:
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pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
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The original is off by one, fix it.
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Cc: stable@vger.kernel.org
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Fixes: 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap")
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Reported-by: Sid Hayn <sidhayn@gmail.com>
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Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Tested-by: Sid Hayn <sidhayn@gmail.com>
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Reviewed-by: Kees Cook <keescook@chromium.org>
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Link: https://lore.kernel.org/r/20211109100203.c61007433ed6.I1dade57aba7de9c4f48d68249adbae62636fd98c@changeid
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Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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---
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--- a/net/mac80211/rx.c
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+++ b/net/mac80211/rx.c
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@@ -364,7 +364,7 @@ ieee80211_add_rx_radiotap_header(struct
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* the compiler to think we have walked past the end of the
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* struct member.
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*/
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- pos = (void *)&rthdr->it_optional[it_present - rthdr->it_optional];
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+ pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
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/* the order of the following fields is important */
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