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

Message ID 20210421234337.GA127225@embeddedor
State New
Headers show
Series [next] wireless: wext-spy: Fix out-of-bounds warning | expand

Commit Message

Gustavo A. R. Silva April 21, 2021, 11:43 p.m. UTC
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 <lkp@intel.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 net/wireless/wext-spy.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Comments

Kees Cook April 22, 2021, 12:22 a.m. UTC | #1
On Wed, Apr 21, 2021 at 06:43:37PM -0500, Gustavo A. R. Silva wrote:
> 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 <lkp@intel.com>

> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>


Thanks!

Reviewed-by: Kees Cook <keescook@chromium.org>


-Kees

> ---

>  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

> 


-- 
Kees Cook
Johannes Berg April 22, 2021, 7:04 a.m. UTC | #2
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
Gustavo A. R. Silva April 22, 2021, 8:03 p.m. UTC | #3
On 4/22/21 02:04, Johannes Berg wrote:
> 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.
> Done: https://lore.kernel.org/lkml/20210422200032.GA168995@embeddedor/
> Seems far simpler (and shorter lines).

Done:
	https://lore.kernel.org/lkml/20210422200032.GA168995@embeddedor/

Thanks for the feedback.
--
Gustavo
diff mbox series

Patch

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);