diff mbox

[v2] mac80211: fix typo in starting baserate for rts_cts_rate_idx

Message ID 1413203681-13846-1-git-send-email-karl.beldan@gmail.com (mailing list archive)
State Not Applicable, archived
Headers show

Commit Message

Karl Beldan Oct. 13, 2014, 12:34 p.m. UTC 
From: Karl Beldan <karl.beldan@rivierawaves.com>

It affects non-(V)HT rates and can lead to selecting an rts_cts rate
that is not a basic rate or way superior to the reference rate (ATM
rates[0] used for the 1st attempt of the protected frame data).

E.g, assuming drivers register growing (bitrate) sorted tables of
ieee80211_rate-s, having :
- rates[0].idx == d'2 and basic_rates == b'10100
will select rts_cts idx b'10011 & ~d'(BIT(2)-1), i.e. 1, likewise
- rates[0].idx == d'2 and basic_rates == b'10001
will select rts_cts idx b'10000
The first is not a basic rate and the second is > rates[0].

Also, wrt severity of the addressed misbehavior, ATM we only have one
rts_cts_rate_idx rather than one per rate table entry, so this idx might
still point to bitrates > rates[1..MAX_RATES].

Fixes: 5253ffb8c9e1 ("mac80211: always pick a basic rate to tx RTS/CTS for pre-HT rates")
Cc: stable@vger.kernel.org
Signed-off-by: Karl Beldan <karl.beldan@rivierawaves.com>
---
 net/mac80211/rate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Johannes Berg Oct. 14, 2014, 9:17 a.m. UTC | #1 
On Mon, 2014-10-13 at 14:34 +0200, Karl Beldan wrote:
> From: Karl Beldan <karl.beldan@rivierawaves.com>
> 
> It affects non-(V)HT rates and can lead to selecting an rts_cts rate
> that is not a basic rate or way superior to the reference rate (ATM
> rates[0] used for the 1st attempt of the protected frame data).

Applied.

johannes

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diff mbox

Patch

diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index 8fdadfd..6081329 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -448,7 +448,7 @@  static void rate_fixup_ratelist(struct ieee80211_vif *vif,
 	 */
 	if (!(rates[0].flags & IEEE80211_TX_RC_MCS)) {
 		u32 basic_rates = vif->bss_conf.basic_rates;
-		s8 baserate = basic_rates ? ffs(basic_rates - 1) : 0;
+		s8 baserate = basic_rates ? ffs(basic_rates) - 1 : 0;
 
 		rate = &sband->bitrates[rates[0].idx];