Re: Permission denied when chainbuilding packages with mock

[Jeremy Allison <jra@samba.org>]

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 :-).