From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: No fallback to /bin/sh in execvp
Date: Fri, 9 Mar 2018 12:01:40 -0500 [thread overview]
Message-ID: <20180309170140.GQ1436@brightrain.aerifal.cx> (raw)
In-Reply-To: <3a04ed7d2f8748a79941a3676658fc25@sap.com>
On Fri, Mar 09, 2018 at 12:23:06PM +0000, Siebenborn, Axel wrote:
> 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 file using /bin/sh.
>
> A simple test:
>
> Create a script file 'prog' without '!#' with the following content and make it executable:
>
> /bin/echo "$@"
>
> 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[] = { "./prog","Hello", "World", (char *)0 };
> ret = execvp ("./prog", cmd);
> int errorNumber = errno;
> printf("Error code: %d. Error message: %s\n", errorNumber, strerror(errorNumber));
> }
>
> 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
> and compatibility wins over sanity,
It's a bug, but one that was considered low priority since real-world
usage is for scripts to start with #!, in which case the kernel
handles invocation. Actually doing what the standard requires here
seems hard since we'd need to allocate storage for the new argv...
Rich
next prev parent reply other threads:[~2018-03-09 17:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-09 12:23 Siebenborn, Axel
2018-03-09 17:01 ` Rich Felker [this message]
2018-03-11 13:47 ` [PATCH] Continue trying execution with "/bin/sh" for execlp and execvp Quentin Rameau
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