2021-04-22 01:28:37

by Gustavo A. R. Silva

Subject: [PATCH][next] 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 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 protected]>
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
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

2021-04-22 07:04:53

by Johannes Berg

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

On Wed, 2021-04-21 at 18:43 -0500, Gustavo A. R. Silva wrote:
>
>   /* 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));
>

It would've been really simple to stick to 80 columns here (and
everywhere in the patch), please do that.

Also, why not just use struct assigments?

spydata->spy_thr_low = threshold->low;

etc.

Seems far simpler (and shorter lines).

johannes