FROMLIST: mwifiex: correct channel stat buffer overflows

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: <>
Cc: Avinash Patil <>
Cc: Xinming Hu <>
Signed-off-by: Brian Norris <>
(am from

TEST=kevin Wifi; verify that survey results don't overflow

Change-Id: Ic0c7b56c7852dcacf055a3003c26789fae794680
Commit-Ready: Brian Norris <>
Tested-by: Brian Norris <>
Reviewed-by: Brian Norris <>
(cherry picked from commit 68a52822444c542b803b4673c63c49254eb46ea3)
Commit-Queue: Brian Norris <>
2 files changed