Re: Permission denied when chainbuilding packages with mock

[Julian Sikorski <belegdol@gmail.com>]

W dniu 10.11.2021 o 08:56, Steve French pisze:
> Fix for the kernel client attached
> 
> 
> On Tue, Nov 9, 2021 at 6:54 PM Jeremy Allison <jra@samba.org> wrote:
>>
>> On Tue, Nov 09, 2021 at 10:26:59AM +0100, Julian Sikorski wrote:
>>> Am 09.11.21 um 09:10 schrieb Steve French:
>>>> Yes - here is a trivial reproducer (excuse the ugly sample cut-n-paste)
>>>>
>>>> #include <stdio.h>
>>>> #include <stdlib.h>
>>>> #include <unistd.h>
>>>> #include <string.h>
>>>> #include <fcntl.h>
>>>> #include <sys/types.h>
>>>> #include <sys/stat.h>
>>>>
>>>> int main(int argc, char *argv[]) {
>>>> char *str = "Text to be added";
>>>> int fd, ret, fsyncrc, fsyncr_rc, openrc, closerc, close2rc;
>>>>
>>>> fd = creat("test.txt", S_IWUSR | S_IRUSR);
>>>> if (fd < 0) {
>>>> perror("creat()");
>>>> exit(1);
>>>> }
>>>> ret = write(fd, str, strlen(str));
>>>> if (ret < 0) {
>>>> perror("write()");
>>>> exit(1);
>>>> }
>>>> openrc = open("test.txt", O_RDONLY);
>>>>          if (openrc < 0) {
>>>>                  perror("creat()");
>>>>                  exit(1);
>>>>          }
>>>> fsyncr_rc = fsync(openrc);
>>>> if (fsyncr_rc < 0)
>>>> perror("fsync()");
>>>> fsyncrc = fsync(fd);
>>>> closerc = close(fd);
>>>> close2rc = close(openrc);
>>>> printf("read fsync rc=%d, write fsync rc=%d, close rc=%d, RO close
>>>> rc=%d\n", fsyncr_rc, fsyncrc, closerc, close2rc);
>>>> }
>>>>
>>>
>>> I can confirm this fails on my machine without nostrictsync:
>>>
>>> $ ./test
>>>
>>> fsync(): Permission denied
>>>
>>> read fsync rc=-1, write fsync rc=0, close rc=0, RO close rc=0
>>>
>>> and works with nostrictsync:
>>>
>>> $ ./test
>>>
>>> read fsync rc=0, write fsync rc=0, close rc=0, RO close rc=0
>>>
>>> So is the bug in the Linux kernel?
>>
>> Yes, it's in the kernel cifsfs module which is forwarding an SMB_FLUSH request
>> (which the spec says must fail on a non-writable handle) to
>> a handle opened as non-writable. Steve hopefully will fix :-).
> 
> 
> 
Thank you. I can confirm that 5.15.1 kernel with this patch applied [1] 
works both with the test case you provided earlier as well as with mock 
chainbuilds without the need for the nostrictsync mount option. Fedora 
kernel-5.14.16-301.fc35.x86_64 was failing without it.

Tested-by: Julian Sikorski <belegdol@gmail.com>

Best regards,
Julian

[1] https://gitlab.com/belegdol/kernel-ark/-/commits/fedora-5.15-cifs-fix/