The minstrel rate controller periodically looks up rate indexes in a sampling table. When accessing a specific row and column, minstrel correctly does a bounds check which, on the surface, appears to handle the case where mi->n_rates < 2. However, mi->sample_idx is actually defined as an unsigned, so the right hand side is taken to be a huge positive number when negative, and the check will always fail. Consequently, the RC will overrun the array and cause random memory corruption when communicating with a peer that has only a single rate. The max value of mi->sample_idx is around 25 so casting to int should have no ill effects. Without the change, uptime is a few minutes under load with an AP that has a single hard-coded rate, and both the AP and STA could potentially crash. With the change, both lasted 12 hours with a steady load. Thanks to Ognjen Maric for providing the single-rate clue so I could reproduce this. This fixes http://bugzilla.kernel.org/show_bug.cgi?id=12490 on the regression list (also http://bugzilla.kernel.org/show_bug.cgi?id=13000). Cc: stable@xxxxxxxxxx Reported-by: Sergey S. Kostyliov <rathamahata@xxxxxxxxx> Reported-by: Ognjen Maric <ognjen.maric@xxxxxxxxx> Signed-off-by: Bob Copeland <me@xxxxxxxxxxxxxxx> --- John & Felix, the patch itself may be too subtle so feel free to do it a different way. However this is as minimal as it gets so I hope it can be applied quickly to stable, and mainline if not too late. net/mac80211/rc80211_minstrel.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c index d9233ec..2681dfa 100644 --- a/net/mac80211/rc80211_minstrel.c +++ b/net/mac80211/rc80211_minstrel.c @@ -216,7 +216,7 @@ minstrel_get_next_sample(struct minstrel_sta_info *mi) unsigned int sample_ndx; sample_ndx = SAMPLE_TBL(mi, mi->sample_idx, mi->sample_column); mi->sample_idx++; - if (mi->sample_idx > (mi->n_rates - 2)) { + if ((int) mi->sample_idx > (mi->n_rates - 2)) { mi->sample_idx = 0; mi->sample_column++; if (mi->sample_column >= SAMPLE_COLUMNS) -- 1.5.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
