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[PATCH] Fix environment traversal when an envvar value is empty
- From: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- To: libc-alpha at sourceware dot org
- Cc: carlos at redhat dot com
- Date: Fri, 20 Jan 2017 00:12:24 +0530
- Subject: [PATCH] Fix environment traversal when an envvar value is empty
- Authentication-results: sourceware.org; auth=none
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.
---
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;
}
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 @@
+/* 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;
+ 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>
--
2.7.4