[Bug 74481] New: It should be documented that using fexecve on a file opened in O_CLOEXEC that is a script cannot possibly work.

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r@public.gmane.org]

https://bugzilla.kernel.org/show_bug.cgi?id=74481

            Bug ID: 74481
           Summary: It should be documented that using fexecve on a file
                    opened in O_CLOEXEC that is a script cannot possibly
                    work.
           Product: Documentation
           Version: unspecified
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P1
         Component: man-pages
          Assignee: documentation_man-pages-ztI5WcYan/vQLgFONoPN62D2FQJk+8+b@public.gmane.org
          Reporter: sstewartgallus00-QKvm5KDIoDa7M0a00MdBSQ@public.gmane.org
        Regression: No

Consider the following program:

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

int main()
{
    int test = open("./test.sh", O_RDONLY | O_CLOEXEC);
    if (-1 == test) {
        perror("open");
    }

    char * const argv[] = {
        (char *) "./test.sh",
        NULL
    };
    char * const env[] = { NULL };
    fexecve(test, argv, env);
    perror("fexecve");

    return 0;
}

and the following script:

#! /usr/bin/env dash

echo 'hello world!'

When the C program is run, it cannot work because by the time the interpreter
has the passed in file name "/proc/self/fd/${FD}" it has already been closed.
This is a strange corner case that should be documented.

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