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Re: [PATCH] Fix environment traversal when an envvar value is empty
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Siddhesh Poyarekar <siddhesh at sourceware dot org>, libc-alpha at sourceware dot org
- Date: Thu, 19 Jan 2017 13:58:44 -0500
- Subject: Re: [PATCH] Fix environment traversal when an envvar value is empty
- Authentication-results: sourceware.org; auth=none
- References: <1484851344-5295-1-git-send-email-siddhesh@sourceware.org>
On 01/19/2017 01:42 PM, Siddhesh Poyarekar wrote:
> The condition when the value of an envvar is empty (not just '\0'),
> the loop in tunables_init gets stuck infinitely because envp is not
> incremented. Fix that by always incrementing envp in the loop.
>
> Added test case (tst-empty-env.c) verifies the fix when the source is
> configured with --enable-hardcoded-path-in-tests, thanks Josh Stone for
> providing the test case. Verified on x86_64.
>
> * elf/dl-tunables (get_next_env): Always advance envp.
> * stdlib/tst-empty-env.c: New test case.
> * stdlib/Makefile (tests): Use it.
Thanks for the fix and test case.
The test needs 2 more comments and it's good to go.
> ---
> elf/dl-tunables.c | 4 ++--
> stdlib/Makefile | 3 +++
> stdlib/tst-empty-env.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 55 insertions(+), 2 deletions(-)
> create mode 100644 stdlib/tst-empty-env.c
>
> diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
> index e0119d1..ba5246a 100644
> --- a/elf/dl-tunables.c
> +++ b/elf/dl-tunables.c
> @@ -80,7 +80,7 @@ get_next_env (char **envp, char **name, size_t *namelen, char **val)
> {
> while (envp != NULL && *envp != NULL)
> {
> - char *envline = *envp;
> + char *envline = *envp++;
> int len = 0;
>
> while (envline[len] != '\0' && envline[len] != '=')
> @@ -94,7 +94,7 @@ get_next_env (char **envp, char **name, size_t *namelen, char **val)
> *namelen = len;
> *val = &envline[len + 1];
>
> - return ++envp;
> + return envp;
Looks good.
> }
>
> return NULL;
> diff --git a/stdlib/Makefile b/stdlib/Makefile
> index 0c09973..5751b5d 100644
> --- a/stdlib/Makefile
> +++ b/stdlib/Makefile
> @@ -81,6 +81,9 @@ tests := tst-strtol tst-strtod testmb testrand testsort testdiv \
> tst-quick_exit tst-thread-quick_exit tst-width \
> tst-width-stdint tst-strfrom tst-strfrom-locale \
> tst-getrandom
> +ifeq ($(build-hardcoded-path-in-tests),yes)
> +tests += tst-empty-env
> +endif
> tests-static := tst-secure-getenv
> ifeq ($(have-cxx-thread_local),yes)
> CFLAGS-tst-quick_exit.o = -std=c++11
> diff --git a/stdlib/tst-empty-env.c b/stdlib/tst-empty-env.c
> new file mode 100644
> index 0000000..48c7f84
> --- /dev/null
> +++ b/stdlib/tst-empty-env.c
> @@ -0,0 +1,50 @@
Need a line with the bug number and what the test does.
> +/* Copyright (C) 2017 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <http://www.gnu.org/licenses/>. */
> +
> +/* Sanity test that passing a NULL value for an envvar does not result in any
> + obscure failures. The test is useful only when the source is configured
> + with --enable-hardcoded-path-in-tests since otherwise the execve just picks
> + up the system dynamic linker. */
> +
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <errno.h>
> +
> +static int
> +do_test (int argc, char **argv)
> +{
> + if (argc == 2)
> + return 0;
> +
> + char envname[] = "FOOBAR";
> + char *filename = program_invocation_name;
Please add a comment referencing the bug and that the environment
must be null and that it hangs and the test will timeout and fail.
> + char *newargv[] = {filename, filename, NULL};
> + char *newenviron[] = {envname, NULL};
> +
> + int ret = execve (filename, newargv, newenviron);
> +
> + if (ret != 0)
> + printf ("execve failed: %m");
> +
> + /* We will reach here only if we fail execve. */
> + return 1;
> +}
> +
> +#define TIMEOUT 3
> +#define TEST_FUNCTION_ARGV do_test
> +#include <support/test-driver.c>
>
--
Cheers,
Carlos.