[PATCH 4.12 30/43] mwifiex: correct channel stat buffer overflows

Greg Kroah-Hartman
2017-09-08T13:23:00Z

From: Brian Norris <briannorris@chromium.org>

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@marvell.com>
Cc: Xinming Hu <huxm@marvell.com>
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Ganapathi Bhat <gbhat@marvell.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/net/wireless/marvell/mwifiex/cfg80211.c
+++ b/drivers/net/wireless/marvell/mwifiex/cfg80211.c
@@ -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);

--- a/drivers/net/wireless/marvell/mwifiex/scan.c
+++ b/drivers/net/wireless/marvell/mwifiex/scan.c
@@ -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;