In C mmap the file for write: Permission denied. Linux - c

Question

This is my code:
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
int main()
{
int fd=open("/home/victor/hello",O_WRONLY);
if(fd<0)
{
perror("Open");
exit(EXIT_FAILURE);
}
struct stat sbuf;
if(fstat(fd, &sbuf)==-1){
perror("stat");
close(fd);
exit(EXIT_FAILURE);
}
void* file_memory= mmap(NULL, sbuf.st_size, PROT_WRITE, MAP_SHARED,fd,0);
if (file_memory == MAP_FAILED ) {
perror("Error mmapping the file");
close(fd);
exit(EXIT_FAILURE);
}
return 0;
}
I tried this too
int fd=open("/home/victor/hello",O_WRONLY|0777);
but it's the same error:
Error mmapping the file: Permission denied
Doing ls -l | grep hola
-rwxrwxrwx 1 victor victor 24 oct 24 01:47 hello
What's wrong?

Answer 1

From the glibc manual, and as already pointed out by R.. and Iwillnotexist Idonotexist above:
Note that most hardware designs cannot support write permission
without read permission, and many do not distinguish read and execute
permission. Thus, you may receive wider permissions than you ask for,
and mappings of write-only files may be denied even if you do not use
PROT_READ.
http://www.gnu.org/software/libc/manual/html_node/Memory_002dmapped-I_002fO.html