Date: Fri, 28 Nov 1997 19:23:34 +0900 (JST) From: kagotani@in.it.okayama-u.ac.jp To: FreeBSD-gnats-submit@FreeBSD.ORG Subject: bin/5172: [2.2.5] /bin/sh dumps core Message-ID: <199711281023.TAA02509@loach.in.it.okayama-u.ac.jp> Resent-Message-ID: <199711281030.CAA06390@hub.freebsd.org>
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>Number: 5172
>Category: bin
>Synopsis: /bin/sh dumps core when exec'ing a bogus script
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Nov 28 02:30:00 PST 1997
>Last-Modified:
>Originator: Hiroto Kagotani
>Organization:
Okayama University, Japan
>Release: FreeBSD 2.2.5-RELEASE i386
>Environment:
On the console or on any terminal emulator running any shell.
>Description:
If the interpreter of an executable script does not exist,
and the directory containing the script is not the last part of PATH
variable, then /bin/sh dumps core when exec'int the script.
>How-To-Repeat:
Create two executable scripts named "a" and "b" as follows:
--- a ---
#!/bin/sh
PATH=.:/bin
b
---------
--- b ---
#!/no/such/file
---------
And type "./a" in your shell. Then, you will get:
% ./a
Segmentation fault - core dumped
%
>Fix:
shellexec() in /bin/sh assumes that tryexec() does not change argv[0].
But execve(2) called in tryexec() changes it.
(I'm not sure whether this is a spec or a bug of execve(2).)
So, my sample fix preserves argv[0] before calling execve(2),
and restores it after.
---------
diff -u /usr/src/bin/sh/exec.c ./exec.c
--- /usr/src/bin/sh/exec.c Mon Aug 25 18:09:46 1997
+++ ./exec.c Fri Nov 28 18:17:22 1997
@@ -164,6 +164,7 @@
char *p;
#endif
+ char *argv0 = argv[0];
#ifdef SYSV
do {
execve(cmd, argv, envp);
@@ -171,6 +172,7 @@
#else
execve(cmd, argv, envp);
#endif
+ argv[0] = argv0;
e = errno;
if (e == ENOEXEC) {
initshellproc();
---------
>Audit-Trail:
>Unformatted:
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