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From: Matthew Story <matthewstory@gmail.com>
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Cc:
Subject: bin/165164: [PATCH][bin] xargs incorrect pointer passed to
waitchildren function
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>Number: 165164
>Category: bin
>Synopsis: [PATCH][bin] xargs incorrect pointer passed to waitchildren function
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Wed Feb 15 05:20:05 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator: Matthew Story
>Release: 9.0
>Organization:
>Environment:
FreeBSD matt9fromouterspace 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Tue Jan 3 07:15:25 UTC 2012 root@obrian.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC i386
>Description:
*argv is manipulated in main to account for Jflag replacement strings (moving argv into av, and leaving *argv a pointer to the first argument following a Jflag replacement string argument || NULL if Jflag not set):
if (*argv == NULL)
cnt = strlen(*bxp++ = echo);
else {
do {
if (Jflag && strcmp(*argv, replstr) == 0) {
char **avj;
jfound = 1;
argv++;
for (avj = argv; *avj; avj++)
cnt += strlen(*avj) + 1;
break;
}
cnt += strlen(*bxp++ = *argv) + 1;
} while (*++argv != NULL);
}
*argv is then passed to parse_input, which passes *av to prerun, which in turn passes *av (locally argv) to waitchildren for diagnostic purposes, while the calls from parse_input itself pass *argv to waitchildren for diagnostic purposes. This incongruity means that calls directly from parse_input (only in cases after EOF has been seen) take either NULL or the first argument after a Jflag string argument as utility name for diagnostic purposes, leading to output like:
xargs: (null): No such file or directory
>How-To-Repeat:
Found this issue after applying patch from PR 165155, which provides POSIX-compliant diagnostic information on exit 255 and children terminated by signals. Condition exists, but is masked for the most part by a race on line 568 (WNOHANG wait immediately following vfork, execvp), if you comment out that line:
/* waitchildren(*argv, 0); */
You will reliably see the following behavior:
$ # this will work unless you have a this_does_not_exist in your PATH
$ echo "hi" | ./xargs -P10 -n1 this_does_not_exist
xargs: (null): No such file or directory
$ # this should read: xargs: hi: No such file or directory
$ echo "this_does_not_exist" | ./xargs -J % % sh
xargs: sh: No such file or directory
You can alternalively apply the patch from PR 165155, and the following will always yield the (null) error condition:
$ jot - 1 10 | ./xargs -P10 -n12 sh -c 'sleep 1; exit 255'
xargs: (null): exited with status 255, aborting
This issue should be resolved prior to patching PR 165155, I will make a note in that ticket as well. Following applying the patch:
$ echo "hi" | ./xargs blah
xargs: blah: No such file or directory
$ echo "hi" | ./xargs -J % % sh
xargs: hi: No such file or directory
And for the PR 165155 case:
$ jot - 1 10 | ./xargs -P10 -n12 sh -c 'sleep 1; exit 255'
xargs: sh: exited with status 255, aborting
>Fix:
Apply patch. This program looks like it needs a larger re-factor, but the solution provided in the patch is to send *av to waitchildren instead of *argv (which is a pointer to the first argument following a Jflag replacement string || null) to make the behavior congruent with the argument list passed to prerun (locally argv).
Patch attached with submission follows:
--- a/usr.bin/xargs/xargs.c 2012-02-14 22:54:29.000000000 -0500
+++ b/usr.bin/xargs/xargs.c 2012-02-14 16:46:37.000000000 -0500
@@ -281,7 +281,7 @@
case EOF:
/* No arguments since last exec. */
if (p == bbp) {
- waitchildren(*argv, 1);
+ waitchildren(*av, 1);
exit(rval);
}
goto arg1;
@@ -368,7 +368,7 @@
}
prerun(argc, av);
if (ch == EOF || foundeof) {
- waitchildren(*argv, 1);
+ waitchildren(*av, 1);
exit(rval);
}
p = bbp;
>Release-Note:
>Audit-Trail:
>Unformatted: