[LTP] [PATCH] syscalls/execve06: Add test for argv[0] = NULL

[Cyril Hrubis]

Hi!
> I wonder why this does not work:
> 	.needs_cmds = (const char *[]) {
> 		"execve06_child",
> 		NULL
> 	},
>
> tst_test.c:1526: TINFO: Timeout per run is 0h 00m 30s
> execve06.c:33: TFAIL: Failed to execute execl01_child: ENOENT (2)
> tst_test.c:395: TBROK: Invalid child (23451) exit value 1

The difference is because the test library adds current directory and
test start directory into $PATH before a test is executed, see
add_paths() in the tst_test.c.

The .needs_cmds is for binaries installed on the system in /usr/bin/
etc. so it does not make much sense to call the add_paths() before we
process the array.

> > +
> > +	pid = SAFE_FORK();
> > +	if (pid == 0) {
> > +		execve(path, argv, envp);
> > +		tst_brk(TFAIL | TERRNO, "Failed to execute execl01_child");
> > +	}
> > +}
> > +
> > +static struct tst_test test = {
> > +	.forks_child = 1,
> > +	.child_needs_reinit = 1,
> > +	.test_all = verify_execve,
> > +	.tags = (const struct tst_tag[]) {
> > +		{"linux-git", "dcd46d897adb"},
> > +		{"CVE", "2021-4034"},
> > +		{}
> > +	}
> > +};
> > diff --git a/testcases/kernel/syscalls/execve/execve06_child.c b/testcases/kernel/syscalls/execve/execve06_child.c
> > new file mode 100644
> > index 000000000..17280d58a
> > --- /dev/null
> > +++ b/testcases/kernel/syscalls/execve/execve06_child.c
> > @@ -0,0 +1,27 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * Copyright (C) 2022 Cyril Hrubis chrubis@suse.cz
> very nit: <chrubis@suse.cz> (missing < >)

Will fix.

> > + */
> > +
> > +#define TST_NO_DEFAULT_MAIN
> > +#include <stdlib.h>
> > +#include "tst_test.h"
> > +
> > +int main(int argc, char *argv[])
> > +{
> > +	tst_reinit();
> > +
> > +	if (argc != 1) {
> > +		tst_res(TFAIL, "argc is %d, expected 1", argc);
> > +		return 0;
> > +	}
> > +
> > +	if (!argv[0]) {
> > +		tst_res(TFAIL, "argv[0] == NULL");
> > +		return 0;
> > +	}
> > +
> > +	tst_res(TPASS, "argv[0] was filled in by kernel");
> 
> Testing matches the description from kernel commit.
> Maybe also test for argv[0] being empty string (to make sure behavior does not
> change, although unlikely it'd change)?

It should be safe either way but I decided to be less specific and only
check that something have been added there.

> I tested it on various kernels, works as expected.
> 
> Reviewed-by: Petr Vorel <pvorel@suse.cz>
> Tested-by: Petr Vorel <pvorel@suse.cz>

I will push it with the added runtest entries and fixed copyright then.

-- 
Cyril Hrubis
chrubis@suse.cz