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authorBob Copeland <me@bobcopeland.com>2009-06-05 08:21:50 -0400
committerJohn W. Linville <linville@tuxdriver.com>2009-06-10 13:27:51 -0400
commit5ee58d7e6ad019675b4090582aec4fa1180d8703 (patch)
tree1f6cb14a99e1b629bf9dcba2879feaf62a463af5
parent4d1d49858c0a5a4fb1be4bc7972754cd640245ba (diff)
mac80211: fix minstrel single-rate memory corruption
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@kernel.org Reported-by: Sergey S. Kostyliov <rathamahata@gmail.com> Reported-by: Ognjen Maric <ognjen.maric@gmail.com> Signed-off-by: Bob Copeland <me@bobcopeland.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
-rw-r--r--net/mac80211/rc80211_minstrel.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/mac80211/rc80211_minstrel.c b/net/mac80211/rc80211_minstrel.c
index 0a11515341ba..b218b98fba7f 100644
--- a/net/mac80211/rc80211_minstrel.c
+++ b/net/mac80211/rc80211_minstrel.c
@@ -215,7 +215,7 @@ 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)