[PATCH] wifi: mac80211: limit injected antenna index in ieee80211_parse_tx_radiotap

[Deepanshu Kartikey <kartikey406@gmail.com>]

When parsing the radiotap header of an injected frame,
ieee80211_parse_tx_radiotap() uses the IEEE80211_RADIOTAP_ANTENNA value
directly as a shift count:

	info->control.antennas |= BIT(*iterator.this_arg);

*iterator.this_arg is an 8-bit value taken straight from the frame
supplied by userspace, so BIT() can be asked to shift by up to 255. That
is undefined behaviour on the unsigned long and is reported by UBSAN:

  UBSAN: shift-out-of-bounds in net/mac80211/tx.c:2174:30
  shift exponent 235 is too large for 64-bit type 'unsigned long'
  Call Trace:
   ieee80211_parse_tx_radiotap+0xadb/0x1950 net/mac80211/tx.c:2174
   ieee80211_monitor_start_xmit+0xb1f/0x1250 net/mac80211/tx.c:2451
   ...
   packet_sendmsg+0x3eb6/0x50f0 net/packet/af_packet.c:3109

info->control.antennas is a 2-bit bitmap (u8 antennas:2), so only antenna
indices 0 and 1 can ever be represented. Ignore any larger value instead
of shifting out of bounds.

Reported-by: syzbot+8e0622f6d9446420271f@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=8e0622f6d9446420271f
Fixes: ef246a1480cc ("wifi: mac80211: support antenna control in injection")
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 net/mac80211/tx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index b487d2330f25..ea7f63e1fc17 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2181,7 +2181,9 @@ bool ieee80211_parse_tx_radiotap(struct sk_buff *skb,
 
 		case IEEE80211_RADIOTAP_ANTENNA:
 			/* this can appear multiple times, keep a bitmap */
-			info->control.antennas |= BIT(*iterator.this_arg);
+			/* control.antennas is only a 2-bit bitmap */
+			if (*iterator.this_arg < 2)
+				info->control.antennas |= BIT(*iterator.this_arg);
 			break;
 
 		case IEEE80211_RADIOTAP_DATA_RETRIES:
-- 
2.43.0