[PATCH] src/t_ofd_locks.c: Reset errno to zero

[PATCH] src/t_ofd_locks.c: Reset errno to zero

[Yang Xu]

It seems I met libcap errno bug again when using libcap-2.48-4.el8.x86_64.
But this time, errno is EINVAL if c program link with lcap.
Lastest upstream libcap doesn't have bug and it should be backport bug.

generic/478 will become not run because of this. To fix this that only
exists on some distributions, reset errno to zero.

Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
---
 src/t_ofd_locks.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/t_ofd_locks.c b/src/t_ofd_locks.c
index e3b15ddc..e77f2659 100644
--- a/src/t_ofd_locks.c
+++ b/src/t_ofd_locks.c
@@ -187,6 +187,8 @@ int main(int argc, char **argv)
 	struct sembuf sop;
 	int opt, ret, retry;
 
+	//avoid libcap errno bug
+	errno = 0;
 	while((opt = getopt(argc, argv, "sgrwo:l:PRWtFd")) != -1) {
 		switch(opt) {
 		case 's':
-- 
2.27.0

Re: [PATCH] src/t_ofd_locks.c: Reset errno to zero

[Darrick J. Wong]

On Thu, Aug 04, 2022 at 02:18:52PM +0800, Yang Xu wrote:
> It seems I met libcap errno bug again when using libcap-2.48-4.el8.x86_64.
> But this time, errno is EINVAL if c program link with lcap.
> Lastest upstream libcap doesn't have bug and it should be backport bug.
> 
> generic/478 will become not run because of this. To fix this that only
> exists on some distributions, reset errno to zero.
> 
> Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
> ---
>  src/t_ofd_locks.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/src/t_ofd_locks.c b/src/t_ofd_locks.c
> index e3b15ddc..e77f2659 100644
> --- a/src/t_ofd_locks.c
> +++ b/src/t_ofd_locks.c
> @@ -187,6 +187,8 @@ int main(int argc, char **argv)
>  	struct sembuf sop;
>  	int opt, ret, retry;
>  
> +	//avoid libcap errno bug
> +	errno = 0;

What sets errno to EINVAL here?  And what actually causes the program to
exit with code 22?

There aren't any library calls prior to this point, right?  Or is this
... libpcap has some initcall that runs quietly in the background before
main starts, so we enter main with errno==EINVAL, which then causes ...
something else to break?

--D

>  	while((opt = getopt(argc, argv, "sgrwo:l:PRWtFd")) != -1) {
>  		switch(opt) {
>  		case 's':
> -- 
> 2.27.0
> 

Re: [PATCH] src/t_ofd_locks.c: Reset errno to zero

[xuyang2018.jy]

on 2022/08/05 23:00, Darrick J. Wong wrote:
> On Thu, Aug 04, 2022 at 02:18:52PM +0800, Yang Xu wrote:
>> It seems I met libcap errno bug again when using libcap-2.48-4.el8.x86_64.
>> But this time, errno is EINVAL if c program link with lcap.
>> Lastest upstream libcap doesn't have bug and it should be backport bug.
>>
>> generic/478 will become not run because of this. To fix this that only
>> exists on some distributions, reset errno to zero.
>>
>> Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
>> ---
>>   src/t_ofd_locks.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/src/t_ofd_locks.c b/src/t_ofd_locks.c
>> index e3b15ddc..e77f2659 100644
>> --- a/src/t_ofd_locks.c
>> +++ b/src/t_ofd_locks.c
>> @@ -187,6 +187,8 @@ int main(int argc, char **argv)
>>   	struct sembuf sop;
>>   	int opt, ret, retry;
>>   
>> +	//avoid libcap errno bug
>> +	errno = 0;
> 
> What sets errno to EINVAL here?  And what actually causes the program to
> exit with code 22?
> 
> There aren't any library calls prior to this point, right?  Or is this
> ... libpcap has some initcall that runs quietly in the background before
> main starts, so we enter main with errno==EINVAL, which then causes ...
> something else to break?
Yes,

#include <stdio.h>
#include <errno.h>
int main(int argc, char **argv)
{
         printf("errno %d\n", errno);
         return 0;
}

gcc test.c -lcap -o test

then run test, errno is EINVAL.

But upstream libcap is ok and it should be a backport bug on libcap 
distribution version.

Best Regards
Yang Xu
> 
> --D
> 
>>   	while((opt = getopt(argc, argv, "sgrwo:l:PRWtFd")) != -1) {
>>   		switch(opt) {
>>   		case 's':
>> -- 
>> 2.27.0
>>

Re: [PATCH] src/t_ofd_locks.c: Reset errno to zero

[Darrick J. Wong]

On Mon, Aug 15, 2022 at 10:06:59AM +0000, xuyang2018.jy@fujitsu.com wrote:
> 
> 
> on 2022/08/05 23:00, Darrick J. Wong wrote:
> > On Thu, Aug 04, 2022 at 02:18:52PM +0800, Yang Xu wrote:
> >> It seems I met libcap errno bug again when using libcap-2.48-4.el8.x86_64.
> >> But this time, errno is EINVAL if c program link with lcap.
> >> Lastest upstream libcap doesn't have bug and it should be backport bug.
> >>
> >> generic/478 will become not run because of this. To fix this that only
> >> exists on some distributions, reset errno to zero.
> >>
> >> Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
> >> ---
> >>   src/t_ofd_locks.c | 2 ++
> >>   1 file changed, 2 insertions(+)
> >>
> >> diff --git a/src/t_ofd_locks.c b/src/t_ofd_locks.c
> >> index e3b15ddc..e77f2659 100644
> >> --- a/src/t_ofd_locks.c
> >> +++ b/src/t_ofd_locks.c
> >> @@ -187,6 +187,8 @@ int main(int argc, char **argv)
> >>   	struct sembuf sop;
> >>   	int opt, ret, retry;
> >>   
> >> +	//avoid libcap errno bug
> >> +	errno = 0;
> > 
> > What sets errno to EINVAL here?  And what actually causes the program to
> > exit with code 22?
> > 
> > There aren't any library calls prior to this point, right?  Or is this
> > ... libpcap has some initcall that runs quietly in the background before
> > main starts, so we enter main with errno==EINVAL, which then causes ...
> > something else to break?
> Yes,
> 
> #include <stdio.h>
> #include <errno.h>
> int main(int argc, char **argv)
> {
>          printf("errno %d\n", errno);
>          return 0;
> }
> 
> gcc test.c -lcap -o test
> 
> then run test, errno is EINVAL.
> 
> But upstream libcap is ok and it should be a backport bug on libcap 
> distribution version.

Yay for still paying for poor decisions of the 1970s in 2022...

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> 
> Best Regards
> Yang Xu
> > 
> > --D
> > 
> >>   	while((opt = getopt(argc, argv, "sgrwo:l:PRWtFd")) != -1) {
> >>   		switch(opt) {
> >>   		case 's':
> >> -- 
> >> 2.27.0
> >>