* [PATCH] nis: Fix stringop-truncation warning with -O3 in nis_local_host.
@ 2023-02-28 12:37 Stefan Liebler
0 siblings, 0 replies; 3+ messages in thread
From: Stefan Liebler @ 2023-02-28 12:37 UTC (permalink / raw)
To: libc-alpha; +Cc: Stefan Liebler
When building with -O3 on s390x/x86_64, I get this stringop-truncation warning
which leads to a build fail:
In function ‘nis_local_host’,
inlined from ‘nis_local_host’ at nis_local_names.c:147:1:
nis_local_names.c:171:11: error: ‘strncpy’ output may be truncated copying between 0 and 1023 bytes from a string of length 1024 [-Werror=stringop-truncation]
171 | strncpy (cp, nis_local_directory (), NIS_MAXNAMELEN - len -1);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We can just ignore this warning as the hostname + '.' + directory-name + '\0' always fits
in __nishostname with length of (NIS_MAXNAMELEN + 1) as there is the runtime check above.
Furthermore as we already know the length of the directory-name, we can also just use
memcpy to copy the directory-name inclusive the NUL-termination.
Note: This werror was introduced with commit
32c7acd46401530fdbd4e98508c9baaa705f8b53
"Replace rawmemchr (s, '\0') with strchr"
---
nis/nis_local_names.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/nis/nis_local_names.c b/nis/nis_local_names.c
index e685255300..699ca04e66 100644
--- a/nis/nis_local_names.c
+++ b/nis/nis_local_names.c
@@ -161,15 +161,19 @@ nis_local_host (void)
if (cp[-1] == '.')
return __nishostname;
- if (len + strlen (nis_local_directory ()) + 1 > NIS_MAXNAMELEN)
+ nis_name local_directory = nis_local_directory ();
+ size_t local_directory_len = strlen (local_directory);
+ if (len + 1 + local_directory_len > NIS_MAXNAMELEN)
{
__nishostname[0] = '\0';
return __nishostname;
}
+ /* We have enough space in __nishostname with length of
+ (NIS_MAXNAMELEN + 1) for
+ hostname + '.' + directory-name + '\0'. */
*cp++ = '.';
- strncpy (cp, nis_local_directory (), NIS_MAXNAMELEN - len -1);
- __nishostname[NIS_MAXNAMELEN] = '\0';
+ memcpy (cp, local_directory, local_directory_len + 1);
}
}
--
2.39.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] nis: Fix stringop-truncation warning with -O3 in nis_local_host.
2023-03-02 10:12 Wilco Dijkstra
@ 2023-03-02 13:26 ` Stefan Liebler
0 siblings, 0 replies; 3+ messages in thread
From: Stefan Liebler @ 2023-03-02 13:26 UTC (permalink / raw)
To: Wilco Dijkstra; +Cc: 'GNU C Library'
On 02.03.23 11:12, Wilco Dijkstra wrote:
> Hi Stefan,
>
>> We can just ignore this warning as the hostname + '.' + directory-name + '\0' always fits
>> in __nishostname with length of (NIS_MAXNAMELEN + 1) as there is the runtime check above.
>> Furthermore as we already know the length of the directory-name, we can also just use
>> memcpy to copy the directory-name inclusive the NUL-termination.
>
> Agreed, that is a much more natural way of doing it.
>
>> Note: This werror was introduced with commit
>> 32c7acd46401530fdbd4e98508c9baaa705f8b53
>> "Replace rawmemchr (s, '\0') with strchr"
>
> The compiler now uses strlen and so it can do more optimization, including
> giving warnings.
>
> LGTM
>
> Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
>
> Cheers,
> Wilco
>
> @@ -161,15 +161,19 @@ nis_local_host (void)
> if (cp[-1] == '.')
> return __nishostname;
>
> - if (len + strlen (nis_local_directory ()) + 1 > NIS_MAXNAMELEN)
> + nis_name local_directory = nis_local_directory ();
> + size_t local_directory_len = strlen (local_directory);
> + if (len + 1 + local_directory_len > NIS_MAXNAMELEN)
>
> OK
> {
> __nishostname[0] = '\0';
> return __nishostname;
> }
>
> + /* We have enough space in __nishostname with length of
> + (NIS_MAXNAMELEN + 1) for
> + hostname + '.' + directory-name + '\0'. */
> *cp++ = '.';
> - strncpy (cp, nis_local_directory (), NIS_MAXNAMELEN - len -1);
> - __nishostname[NIS_MAXNAMELEN] = '\0';
> + memcpy (cp, local_directory, local_directory_len + 1);
>
> OK
I've just committed the patch.
Thanks,
Stefan
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] nis: Fix stringop-truncation warning with -O3 in nis_local_host.
@ 2023-03-02 10:12 Wilco Dijkstra
2023-03-02 13:26 ` Stefan Liebler
0 siblings, 1 reply; 3+ messages in thread
From: Wilco Dijkstra @ 2023-03-02 10:12 UTC (permalink / raw)
To: stli; +Cc: 'GNU C Library'
Hi Stefan,
> We can just ignore this warning as the hostname + '.' + directory-name + '\0' always fits
> in __nishostname with length of (NIS_MAXNAMELEN + 1) as there is the runtime check above.
> Furthermore as we already know the length of the directory-name, we can also just use
> memcpy to copy the directory-name inclusive the NUL-termination.
Agreed, that is a much more natural way of doing it.
> Note: This werror was introduced with commit
> 32c7acd46401530fdbd4e98508c9baaa705f8b53
> "Replace rawmemchr (s, '\0') with strchr"
The compiler now uses strlen and so it can do more optimization, including
giving warnings.
LGTM
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Cheers,
Wilco
@@ -161,15 +161,19 @@ nis_local_host (void)
if (cp[-1] == '.')
return __nishostname;
- if (len + strlen (nis_local_directory ()) + 1 > NIS_MAXNAMELEN)
+ nis_name local_directory = nis_local_directory ();
+ size_t local_directory_len = strlen (local_directory);
+ if (len + 1 + local_directory_len > NIS_MAXNAMELEN)
OK
{
__nishostname[0] = '\0';
return __nishostname;
}
+ /* We have enough space in __nishostname with length of
+ (NIS_MAXNAMELEN + 1) for
+ hostname + '.' + directory-name + '\0'. */
*cp++ = '.';
- strncpy (cp, nis_local_directory (), NIS_MAXNAMELEN - len -1);
- __nishostname[NIS_MAXNAMELEN] = '\0';
+ memcpy (cp, local_directory, local_directory_len + 1);
OK
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-02-28 12:37 [PATCH] nis: Fix stringop-truncation warning with -O3 in nis_local_host Stefan Liebler
2023-03-02 10:12 Wilco Dijkstra
2023-03-02 13:26 ` Stefan Liebler
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