2015年11月20日 下午2:46於 "Ted Unangst" <t...@tedunangst.com>寫道：
>
> 游俊德 wrote:
> > Hello,
> >
> > I have a question about source code of shm_open and sem_open functions.
> >
> > int
> > shm_open(const char *path, int flags, mode_t mode)
> > {
> > ........ (skipped) ....
> >
> > if (sb,st_uid != getuid()) {
> > close(fd);
> > errno = EPERM;
> > return -1;
> > }
> >
> > ........ (skipped) ....
> > }
> >
> > I know the UID comparison is used to avoid share memory accessed by
> > different user. Similar code also existed in sem_open function.
> >
> > My question is, why it is getuid(), why not use geteuid()?
> > I am not sure if it is bug or not, but I think it is more reasonable
> > if it checked
> > by effective user id,
>
> geteuid may be better. though i would hope the difference doesn't matter.
The difference is very important for me.
In my application, I am root and change to different uid, create semaphore
and share memory, make some hand sharking to client app with different uid.
May I give a patch to fix it?
