Re: [Bug #12490] ath5k related kernel panic in 2.6.29-rc1

Bob Copeland
2009-04-08T00:46:44Z

On Tue, Apr 07, 2009 at 12:03:45PM +0200, Johannes Berg wrote:
>
> > Anyway here's a patch to buy some time. Johannes, would this be
> > an acceptable band-aid for now?
>
> This is going to make it print two warnings for one occurrence of the
> problem though. I'd much prefer to put something into minstrel.c to
> catch when _it_ returns bogus values and in that case return 0, that way
> at least the bandaid is restricted to the code it patches up.

Ok, then maybe something like this?

I think this covers most of the bases: if the driver is returning crap or
the ->cb gets corrupted, it'll get caught in tx_status. If minstrel
stuffs a -1 in the first slot for any other reason we'll get a warning
before get_tx_rate and a hopefully valid index gets substituted.

diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index 3824990..1cf7152 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -181,6 +181,11 @@ minstrel_tx_status(void *priv, struct ieee80211_supported_band *sband,
if (ar[i].idx < 0)
break;

+ if (WARN(ar[i].idx >= mi->n_rates,
+ "minstrel: invalid rate report %d (n=%d)\n",
+ ar[i].idx, mi->n_rates))
+ break;
+
ndx = rix_to_ndx(mi, ar[i].idx);
mi->r[ndx].attempts += ar[i].count;

@@ -328,7 +333,7 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
ar[0].count = mp->max_retry;
ar[1].idx = mi->lowest_rix;
ar[1].count = mp->max_retry;
- return;
+ goto done;
}

/* MRR setup */
@@ -346,6 +351,10 @@ minstrel_get_rate(void *priv, struct ieee80211_sta *sta,
ar[i].idx = mi->r[mrr_ndx[i - 1]].rix;
ar[i].count = mi->r[mrr_ndx[i - 1]].adjusted_retry_count;
}
+
+done:
+ if (WARN_ON(ar[0].idx < 0))
+ ar[0].idx = rate_lowest_index(sband, sta);
}

--
Bob Copeland %% www.bobcopeland.com