POSIX共享内存和semaphores的权限被open调用错误地设置了

这可能是 umask .

Citing the manpage of shm_open :

   O_CREAT    Create  the  shared memory object if it does not exist.  The user and
              group ownership of the object are taken from the corresponding effec‐
              tive IDs of the calling process, and the object's permission bits are
              set according to the low-order 9 bits of mode, except that those bits
              set in the process file mode creation mask (see umask(2)) are cleared
              for the new object.  A set of macro constants which can  be  used  to
              define  mode  is  listed  in open(2).  (Symbolic definitions of these
              constants can be obtained by including <sys/stat.h>.)
因此，为了允许创建可写入世界的文件，你需要设置一个允许它的掩码，例如。
umask(0);
像这样设置，umask就不会再影响所创建文件的任何权限。然而，你应该注意到，如果你在没有明确指定权限的情况下创建另一个文件，它也将是世界可写的。
因此，你可能只想暂时清除umask，然后再恢复它。
#include <sys/types.h>
#include <sys/stat.h>
void yourfunc()
    // store old
    mode_t old_umask = umask(0);
    int fd = shm_open(SHARE_MEM_NAME,O_RDWR | O_CREAT,0606);
    // restore old
    umask(old_umask);