Checked on x86_64-linux-gnu and i686-linux-gnu.
---
stdlib/Makefile | 3 +-
stdlib/tst-canon-bz26341.c | 108 ++++++++++++++++++
support/support_set_small_thread_stack_size.c | 12 +-
support/xthread.h | 2 +
4 files changed, 121 insertions(+), 4 deletions(-)
create mode 100644 stdlib/tst-canon-bz26341.c
diff --git a/stdlib/Makefile b/stdlib/Makefile
index 29b7cd7071..6518d8993b 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -86,7 +86,7 @@ tests := tst-strtol tst-strtod testmb testrand
testsort testdiv \
tst-makecontext-align test-bz22786 tst-strtod-nan-sign \
tst-swapcontext1 tst-setcontext4 tst-setcontext5 \
tst-setcontext6 tst-setcontext7 tst-setcontext8 \
- tst-setcontext9 tst-bz20544
+ tst-setcontext9 tst-bz20544 tst-canon-bz26341
tests-internal := tst-strtod1i tst-strtod3 tst-strtod4 tst-strtod5i \
tst-tls-atexit tst-tls-atexit-nodelete
@@ -101,6 +101,7 @@ LDLIBS-test-atexit-race = $(shared-thread-library)
LDLIBS-test-at_quick_exit-race = $(shared-thread-library)
LDLIBS-test-cxa_atexit-race = $(shared-thread-library)
LDLIBS-test-on_exit-race = $(shared-thread-library)
+LDLIBS-tst-canon-bz26341 = $(shared-thread-library)
LDLIBS-test-dlclose-exit-race = $(shared-thread-library) $(libdl)
LDFLAGS-test-dlclose-exit-race = $(LDFLAGS-rdynamic)
diff --git a/stdlib/tst-canon-bz26341.c b/stdlib/tst-canon-bz26341.c
new file mode 100644
index 0000000000..63474bddaa
--- /dev/null
+++ b/stdlib/tst-canon-bz26341.c
@@ -0,0 +1,108 @@
+/* Check if realpath does not consume extra stack space based on symlink
+ existance in the path (BZ #26341)
+ Copyright (C) 2020 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
+ <https://www.gnu.org/licenses/>. */
+
+#include <stdlib.h>
+#include <string.h>
+#include <sys/param.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+#include <support/xthread.h>
+
+static char *filename;
+static size_t filenamelen;
+static char *linkname;
+
+static int
+maxsymlinks (void)
+{
+#ifdef MAXSYMLINKS
+ return MAXSYMLINKS;
+#else
+ long int sysconf_symloop_max = sysconf (_SC_SYMLOOP_MAX);
+ return sysconf_symloop_max <= 0
+ ? _POSIX_SYMLOOP_MAX
+ : sysconf_symloop_max;
+#endif
+}
+
+#ifndef PATH_MAX
+# define PATH_MAX 1024
+#endif
+
+static void
+create_link (void)
+{
+ int fd = create_temp_file ("tst-canon-bz26341", &filename);
+ TEST_VERIFY_EXIT (fd != -1);
+ xclose (fd);
+
+ char *prevlink = filename;
+ int maxlinks = maxsymlinks ();
+ for (int i = 0; i < maxlinks; i++)
+ {
+ linkname = xasprintf ("%s%d", filename, i);
+ xsymlink (prevlink, linkname);
+ add_temp_file (linkname);
+ prevlink = linkname;
+ }
+
+ filenamelen = strlen (filename);
+}
+
+static void *
+do_realpath (void *arg)
+{
+ /* Old implementation of realpath allocates a PATH_MAX using alloca
+ for each symlink in the path, leading to MAXSYMLINKS times PATH_MAX
+ maximum stack usage.
+ This stack allocations tries fill the thread allocated stack minus
+ both the thread (plus some slack) and the realpath (plus some slack).
+ If realpath uses more than 2 * PATH_MAX plus some slack it will trigger
+ a stackoverflow. */
+
+ const size_t realpath_usage = 2 * PATH_MAX + 1024;
+ const size_t thread_usage = 1 * PATH_MAX + 1024;
+ size_t stack_size = support_small_thread_stack_size ()
+ - realpath_usage - thread_usage;
+ char stack[stack_size];
+ char *resolved = stack + stack_size - thread_usage + 1024;
+
+ char *p = realpath (linkname, resolved);
+ TEST_VERIFY (p != NULL);
+ TEST_COMPARE_BLOB (resolved, filenamelen, filename, filenamelen);
+
+ return NULL;
+}
+
+static int
+do_test (void)
+{
+ create_link ();
+
+ pthread_t th = xpthread_create (support_small_stack_thread_attribute (),
+ do_realpath, NULL);
+ xpthread_join (th);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/support_set_small_thread_stack_size.c
b/support/support_set_small_thread_stack_size.c
index 69d66e97db..74a0e38a72 100644
--- a/support/support_set_small_thread_stack_size.c
+++ b/support/support_set_small_thread_stack_size.c
@@ -20,8 +20,8 @@
#include <pthread.h>
#include <support/xthread.h>
-void
-support_set_small_thread_stack_size (pthread_attr_t *attr)
+size_t
+support_small_thread_stack_size (void)
{
/* Some architectures have too small values for PTHREAD_STACK_MIN
which cannot be used for creating threads. Ensure that the stack
@@ -31,5 +31,11 @@ support_set_small_thread_stack_size (pthread_attr_t *attr)
if (stack_size < PTHREAD_STACK_MIN)
stack_size = PTHREAD_STACK_MIN;
#endif
- xpthread_attr_setstacksize (attr, stack_size);
+ return stack_size;
+}
+
+void
+support_set_small_thread_stack_size (pthread_attr_t *attr)
+{
+ xpthread_attr_setstacksize (attr, support_small_thread_stack_size ());
}
diff --git a/support/xthread.h b/support/xthread.h
index 05f8d4a7d9..6ba2f5a18b 100644
--- a/support/xthread.h
+++ b/support/xthread.h
@@ -78,6 +78,8 @@ void xpthread_attr_setguardsize (pthread_attr_t *attr,
/* Set the stack size in ATTR to a small value, but still large enough
to cover most internal glibc stack usage. */
void support_set_small_thread_stack_size (pthread_attr_t *attr);
+/* Return the stack size used on support_set_small_thread_stack_size. */
+size_t support_small_thread_stack_size (void);
/* Return a pointer to a thread attribute which requests a small
stack. The caller must not free this pointer. */
--
2.25.1
