Subject: [PATCH][next] wireless: wext-spy: Fix out-of-bounds warning

From: "Gustavo A. R. Silva" <[email-masked]>
Date: Wed, 21 Apr 2021 18:43:37 -0500

Fix the following out-of-bounds warning:

net/wireless/wext-spy.c:178:2: warning: 'memcpy' offset [25, 28] from the object at 'threshold' is out of the bounds of referenced subobject 'low' with type 'struct iw_quality' at offset 20 [-Warray-bounds]

The problem is that the original code is trying to copy data into a
couple of struct members adjacent to each other in a single call to
memcpy(). This causes a legitimate compiler warning because memcpy()
overruns the length of &threshold.low and &spydata->spy_thr_low. As
these are just a couple of members, fix this by copying each one of
them in separate calls to memcpy().

Also, while there, use sizeof(threshold.qual) instead of
sizeof(struct iw_quality)) in another call to memcpy()
above.

This helps with the ongoing efforts to globally enable -Warray-bounds
and get us closer to being able to tighten the FORTIFY_SOURCE routines
on memcpy().

Link: https://github.com/KSPP/linux/issues/109
Reported-by: kernel test robot <[email-masked]>
Signed-off-by: Gustavo A. R. Silva <[email-masked]>
---
 net/wireless/wext-spy.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/wireless/wext-spy.c b/net/wireless/wext-spy.c
index 33bef22e44e9..bb2de7c6bee4 100644
--- a/net/wireless/wext-spy.c
+++ b/net/wireless/wext-spy.c
@@ -120,8 +120,8 @@ int iw_handler_set_thrspy(struct net_device *	dev,
 		return -EOPNOTSUPP;
 
 	/* Just do it */
-	memcpy(&(spydata->spy_thr_low), &(threshold->low),
-	       2 * sizeof(struct iw_quality));
+	memcpy(&spydata->spy_thr_low, &threshold->low, sizeof(threshold->low));
+	memcpy(&spydata->spy_thr_high, &threshold->high, sizeof(threshold->high));
 
 	/* Clear flag */
 	memset(spydata->spy_thr_under, '\0', sizeof(spydata->spy_thr_under));
@@ -173,10 +173,10 @@ static void iw_send_thrspy_event(struct net_device *	dev,
 	memcpy(threshold.addr.sa_data, address, ETH_ALEN);
 	threshold.addr.sa_family = ARPHRD_ETHER;
 	/* Copy stats */
-	memcpy(&(threshold.qual), wstats, sizeof(struct iw_quality));
+	memcpy(&threshold.qual, wstats, sizeof(threshold.qual));
 	/* Copy also thresholds */
-	memcpy(&(threshold.low), &(spydata->spy_thr_low),
-	       2 * sizeof(struct iw_quality));
+	memcpy(&threshold.low, &spydata->spy_thr_low, sizeof(threshold.low));
+	memcpy(&threshold.high, &spydata->spy_thr_high, sizeof(threshold.high));
 
 	/* Send event to user space */
 	wireless_send_event(dev, SIOCGIWTHRSPY, &wrqu, (char *) &threshold);
-- 
2.27.0