[PATCH 4.4 15/31] mwifiex: correct channel stat buffer overflows

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Brian Norris <briannorris@xxxxxxxxxxxx>

commit 4b5dde2d6234ff5bc68e97e6901d1f2a0a7f3749 upstream.

mwifiex records information about various channels as it receives scan
information. It does this by appending to a buffer that was sized
to the max number of supported channels on any band, but there are
numerous problems:

(a) scans can return info from more than one band (e.g., both 2.4 and 5
    GHz), so the determined "max" is not large enough
(b) some firmware appears to return multiple results for a given
    channel, so the max *really* isn't large enough
(c) there is no bounds checking when stashing these stats, so problems
    (a) and (b) can easily lead to buffer overflows

Let's patch this by setting a slightly-more-correct max (that accounts
for a combination of both 2.4G and 5G bands) and adding a bounds check
when writing to our statistics buffer.

Due to problem (b), we still might not properly report all known survey
information (e.g., with "iw <dev> survey dump"), since duplicate results
(or otherwise "larger than expected" results) will cause some
truncation. But that's a problem for a future bugfix.

(And because of this known deficiency, only log the excess at the WARN
level, since that isn't visible by default in this driver and would
otherwise be a bit too noisy.)

Fixes: bf35443314ac ("mwifiex: channel statistics support for mwifiex")
Cc: Avinash Patil <patila@xxxxxxxxxxx>
Cc: Xinming Hu <huxm@xxxxxxxxxxx>
Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Reviewed-by: Ganapathi Bhat <gbhat@xxxxxxxxxxx>
Signed-off-by: Kalle Valo <kvalo@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/net/wireless/mwifiex/cfg80211.c |    2 +-
 drivers/net/wireless/mwifiex/scan.c     |    6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/net/wireless/mwifiex/cfg80211.c
+++ b/drivers/net/wireless/mwifiex/cfg80211.c
@@ -3740,7 +3740,7 @@ int mwifiex_init_channel_scan_gap(struct
 	if (adapter->config_bands & BAND_A)
 		n_channels_a = mwifiex_band_5ghz.n_channels;
 
-	adapter->num_in_chan_stats = max_t(u32, n_channels_bg, n_channels_a);
+	adapter->num_in_chan_stats = n_channels_bg + n_channels_a;
 	adapter->chan_stats = vmalloc(sizeof(*adapter->chan_stats) *
 				      adapter->num_in_chan_stats);
 
--- a/drivers/net/wireless/mwifiex/scan.c
+++ b/drivers/net/wireless/mwifiex/scan.c
@@ -2170,6 +2170,12 @@ mwifiex_update_chan_statistics(struct mw
 					      sizeof(struct mwifiex_chan_stats);
 
 	for (i = 0 ; i < num_chan; i++) {
+		if (adapter->survey_idx >= adapter->num_in_chan_stats) {
+			mwifiex_dbg(adapter, WARN,
+				    "FW reported too many channel results (max %d)\n",
+				    adapter->num_in_chan_stats);
+			return;
+		}
 		chan_stats.chan_num = fw_chan_stats->chan_num;
 		chan_stats.bandcfg = fw_chan_stats->bandcfg;
 		chan_stats.flags = fw_chan_stats->flags;