Patch "mwifiex: correct channel stat buffer overflows" has been added to the 4.12-stable tree

This is a note to let you know that I've just added the patch titled

mwifiex: correct channel stat buffer overflows

to the 4.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mwifiex-correct-channel-stat-buffer-overflows.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Brian Norris <[email protected]>
Date: Thu, 29 Jun 2017 18:23:54 -0700
Subject: mwifiex: correct channel stat buffer overflows

From: Brian Norris <[email protected]>

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.)

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

@@ -4221,7 +4221,7 @@ 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);
 

@@ -2492,6 +2492,12 @@ 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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.12/mwifiex-correct-channel-stat-buffer-overflows.patch