* kill builtin argument parsing
@ 2016-06-05 16:35 Matthew Malcomson
2016-06-06 0:31 ` Bart Schaefer
0 siblings, 1 reply; 2+ messages in thread
From: Matthew Malcomson @ 2016-06-05 16:35 UTC (permalink / raw)
To: zsh-workers
Hello there,
I recently mistakenly used arguments for the /bin/kill binary with the
zsh kill builtin and noticed something strange that I think should be
improved.
The command line I used was:
kill -1 -- <any pid>
which ends up killing the current Zsh process.
This is because the pid valid argument check at Src/builtin.c:2572 uses
isanum() that just asserts that all characters in the string are either
'-' or a digit.
When the string "--" is parsed as a digit with atoi() in Src/jobs.c:2572
it returns '0' which is passed to kill(2) syscall.
I'm not sure whether to suggest changing the isanum() function, or the
check in bin_kill() that relies on it.
I would personally change the isanum() function, as a cursory reading of
the two places it's used appear to not require this particular behaviour
(the other place it's used in Src/jobs.c:2193 doesn't appear to have any
negative consequences either way), but the comment above this isanum()
function clearly shows it was a known behaviour, so there may be a
reason I'm missing.
Either way I think the behaviour is surprising enough and possible
enough to be worth changing.
Cheers
MM
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: kill builtin argument parsing
2016-06-05 16:35 kill builtin argument parsing Matthew Malcomson
@ 2016-06-06 0:31 ` Bart Schaefer
0 siblings, 0 replies; 2+ messages in thread
From: Bart Schaefer @ 2016-06-06 0:31 UTC (permalink / raw)
To: zsh-workers
On Jun 5, 5:35pm, Matthew Malcomson wrote:
}
} The command line I used was:
} kill -1 -- <any pid>
} which ends up killing the current Zsh process.
This is a little odd, because the code that examines argv[1] to see if
it is -l or -s or -n or -<NUM> or -<NAME> also checks whether it is
"--", but then simply discards that. So you can do
kill -- 12345
to send the default signal to process 12345, you just can't precede
the "--" with any of the other options. I suspect this is so that
you can do
kill -- -12345
i.e. force a negative PID in order to kill a process group instead of
having that interpreted as signal number 12345.
Anyway this is clearly incomplete handling of "--". The patch below
means that
kill -- --
will report "not enough arguments" rather than complaining about either
an invalid signal or an invalid PID, but that's probably OK.
diff --git a/Src/jobs.c b/Src/jobs.c
index 2a9dbe7..04cb6b3 100644
--- a/Src/jobs.c
+++ b/Src/jobs.c
@@ -2527,6 +2527,10 @@ bin_kill(char *nam, char **argv, UNUSED(Options ops), UNUSED(int func))
argv++;
}
+ /* Discard the standard "-" and "--" option breaks */
+ if (*argv && (*argv)[0] == '-' && (!(*argv)[1] || (*argv)[1] == '-'))
+ argv++;
+
if (!*argv) {
zwarnnam(nam, "not enough arguments");
return 1;
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