wireless: wext-spy: Fix out-of-bounds warning

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 struct members, fix this by using direct
assignments, instead of memcpy().

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 <lkp@intel.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210422200032.GA168995@embeddedor
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/wireless/wext-spy.c b/net/wireless/wext-spy.c
index 33bef22..b379a03 100644 (file)
--- 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));
+       spydata->spy_thr_low = threshold->low;
+       spydata->spy_thr_high = threshold->high;
 
        /* Clear flag */
        memset(spydata->spy_thr_under, '\0', sizeof(spydata->spy_thr_under));
@@ -147,8 +147,8 @@ int iw_handler_get_thrspy(struct net_device *       dev,
                return -EOPNOTSUPP;
 
        /* Just do it */
-       memcpy(&(threshold->low), &(spydata->spy_thr_low),
-              2 * sizeof(struct iw_quality));
+       threshold->low = spydata->spy_thr_low;
+       threshold->high = spydata->spy_thr_high;
 
        return 0;
 }
@@ -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));
+       threshold.qual = *wstats;
        /* Copy also thresholds */
-       memcpy(&(threshold.low), &(spydata->spy_thr_low),
-              2 * sizeof(struct iw_quality));
+       threshold.low = spydata->spy_thr_low;
+       threshold.high = spydata->spy_thr_high;
 
        /* Send event to user space */
        wireless_send_event(dev, SIOCGIWTHRSPY, &wrqu, (char *) &threshold);