Date: Sat, 16 Sep 2000 14:50:11 -0400 (EDT) From: rwatson@freebsd.org To: FreeBSD-gnats-submit@freebsd.org Subject: bin/21315: Bizarre shell interpreter failure mode Message-ID: <200009161850.OAA03050@fledge.watson.org>
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>Number: 21315
>Category: bin
>Synopsis: Shells often behave oddly when executing shell scripts
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sat Sep 16 12:00:01 PDT 2000
>Closed-Date:
>Last-Modified:
>Originator: Robert Watson
>Release: FreeBSD 4.1-STABLE i386
>Organization:
>Environment:
FreeBSD mocking.southhadley.watson.org 4.1-STABLE FreeBSD 4.1-STABLE #1: Mon Aug 7 14:13:19 EDT 2000 root@numocking.gw.tislabs.com:/usr/src/sys/compile/MOCKING i386
>Description:
Shells appear to behave oddly when executing shell scripts in a number of
situations.
(1) When the kernel discovers that the interpreter used is another
interpreter, it generally returns ``Exec format error'' (ENOEXEC).
However, when csh and sh find themselves in the same situation, they
don't return that error, they execute the script using their own
interpreter.
(2) When in single-user mode, the sh shell appears to assume that any
script it runs should be executed using its own interpreter, not
the interpreter at the top of the file. In multi-user mode, this
appears to work fine.
>How-To-Repeat:
(1)
$ cat /tmp/test1
#!/tmp/test2
echo This is test1, meant to execute using test2
$ cat /tmp/test2
#!/tmp/test1
echo This is test2, meant to execute with test1
$ /tmp/test1
This is test1, meant to execute using test2
$ /tmp/test2
This is test2, meant to execute with test1
$
I.e., executing test1 resulted in sh executing it, instead of ENOEXEC.
Similarly with test2. Neither resulted in a recursive call, which is
good. This seems like a poor failure-mode -- it's inconsistent with
the kernel execve() implementation's failure mode, and it runs things
when you would hope that it wouldn't (always bad).
(2)
Boot to single user mode, select /bin/sh as the shell, and attempt to
execute a shell script relying on csh features.
>Fix:
Not attached.
>Release-Note:
>Audit-Trail:
>Unformatted:
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