fopen vs. os::fopen and automatic closing of the file on exec

[Baesken, Matthias]

Hi David , yes you are probably right, simply adding it always in the jdk  coding  would lead to problems .
On the other hand,  do I  have the  option  to set O_CLOEXEC in some way for  the jdk  open calls , in case I want it ?

Best regards, Matthias



> Hi Matthias,
> 
> On 28/01/2020 11:44 pm, Baesken, Matthias wrote:
> > Hi David, thanks for looking into it .
> >
> > While checking other  open(64) calls, I found  the fileOpen / handleOpen
> calls  in java.base .
> > Looks like  they  miss  so far  setting  FD_CLOEXEC /   O_CLOEXEC  , it isn’t
> done in the callers of those functions  and it is also not (silently) added in the
> fileOpen/handleOpen function itself  (like HS does in os::open ).
> > See :
> >
> > 73FD
> > 74handleOpen(const char *path, int oflag, int mode) {
> > 75    FD fd;
> > 76    RESTARTABLE(open64(path, oflag, mode), fd);
> > 77    if (fd != -1) {
> > 78        struct stat64 buf64;
> > 79        int result;
> > 80        RESTARTABLE(fstat64(fd, &buf64), result);
> > 81        if (result != -1) {
> > 82            if (S_ISDIR(buf64.st_mode)) {
> > 83                close(fd);
> > 84                errno = EISDIR;
> > 85                fd = -1;
> > 86            }
> > 87        } else {
> > 88            close(fd);
> > 89            fd = -1;
> > 90        }
> > 91    }
> > 92    return fd;
> > 93}
> >
> > 95void
> > 96fileOpen(JNIEnv *env, jobject this, jstring path, jfieldID fid, int flags)
> > 97{
> > .....
> > 107        fd = handleOpen(ps, flags, 0666);
> > ....
> > 122}
> >
> > 56JNIEXPORT void JNICALL
> > 57Java_java_io_FileOutputStream_open0(JNIEnv *env, jobject this,
> > 58                                    jstring path, jboolean append) {
> > 59    fileOpen(env, this, path, fos_fd,
> > 60             O_WRONLY | O_CREAT | (append ? O_APPEND : O_TRUNC));
> > 61}
> >
> > 59JNIEXPORT void JNICALL
> > 60Java_java_io_FileInputStream_open0(JNIEnv *env, jobject this, jstring
> path) {
> > 61    fileOpen(env, this, path, fis_fd, O_RDONLY);
> > 62}
> >
> >
> > Is this something that should be changed too ?
> 
> I think not. Unless those public API's are specified to open a file in a
> specific mode, like close-on-exec, then they should not do that by default.
> 
> We should only be doing close-on-exec on internally used files.
> 
> David
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