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From: "Siebenborn, Axel" <axel.siebenborn@sap.com>
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Subject: No fallback to /bin/sh in execvp
Date: Fri, 9 Mar 2018 12:23:06 +0000
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Hi,

I encountered a problem with execvp with musl.
Trying to execute shell scripts without #! fails with ENOEXEC.
However, according to the standard, execvp should fallback to execute the f=
ile using /bin/sh.

A simple test:

Create a  script file 'prog'  without '!#' with the following content and m=
ake it executable:

/bin/echo "$@"=20

Compile and run the following c-program:

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>

int main (){
  int ret;
  char *cmd[] =3D { "./prog","Hello", "World", (char *)0 };
  ret =3D execvp ("./prog", cmd);
  int errorNumber =3D errno;
  printf("Error code: %d. Error message: %s\n", errorNumber, strerror(error=
Number));
}

With musl the execution results in the following error:

Error code: 8. Error message: Exec format error

With glibs 'Hello world' is printed.

Is this a bug, that will be fixed someday or intended behavior for security=
 reasons.

I think it's a quiet a strange way to execute shell commands. However, some=
 ancient code might rely on this=20
and compatibility wins over sanity,

Kind regards,
Axel