package/kernel/mac80211/patches/subsys/308-mac80211-fix-radiotap-header-generation.patch

   1 From: Johannes Berg <johannes.berg@intel.com>
   2 Date: Tue, 9 Nov 2021 10:02:04 +0100
   3 Subject: [PATCH] mac80211: fix radiotap header generation
   4
   5 In commit 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header
   6 bitmap") we accidentally pointed the position to the wrong place, so
   7 we overwrite a present bitmap, and thus cause all kinds of trouble.
   8
   9 To see the issue, note that the previous code read:
  10
  11   pos = (void *)(it_present + 1);
  12
  13 The requirement now is that we need to calculate pos via it_optional,
  14 to not trigger the compiler hardening checks, as:
  15
  16   pos = (void *)&rthdr->it_optional[...];
  17
  18 Rewriting the original expression, we get (obviously, since that just
  19 adds "+ x - x" terms):
  20
  21   pos = (void *)(it_present + 1 + rthdr->it_optional - rthdr->it_optional)
  22
  23 and moving the "+ rthdr->it_optional" outside to be used as an array:
  24
  25   pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
  26
  27 The original is off by one, fix it.
  28
  29 Cc: stable@vger.kernel.org
  30 Fixes: 8c89f7b3d3f2 ("mac80211: Use flex-array for radiotap header bitmap")
  31 Reported-by: Sid Hayn <sidhayn@gmail.com>
  32 Signed-off-by: Johannes Berg <johannes.berg@intel.com>
  33 Tested-by: Sid Hayn <sidhayn@gmail.com>
  34 Reviewed-by: Kees Cook <keescook@chromium.org>
  35 Link: https://lore.kernel.org/r/20211109100203.c61007433ed6.I1dade57aba7de9c4f48d68249adbae62636fd98c@changeid
  36 Signed-off-by: Johannes Berg <johannes.berg@intel.com>
  37 ---
  38
  39 --- a/net/mac80211/rx.c
  40 +++ b/net/mac80211/rx.c
  41 @@ -364,7 +364,7 @@ ieee80211_add_rx_radiotap_header(struct
  42          * the compiler to think we have walked past the end of the
  43          * struct member.
  44          */
  45 -       pos = (void *)&rthdr->it_optional[it_present - rthdr->it_optional];
  46 +       pos = (void *)&rthdr->it_optional[it_present + 1 - rthdr->it_optional];
  47
  48         /* the order of the following fields is important */
  49