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Linux: Add io/tst-o_path-locks test

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The O_PATH-based fchmodat emulation will rely on the fact that closing
an O_PATH descriptor never releases POSIX advisory locks, so this
commit adds a test case for this behavior.
This commit is contained in:
Florian Weimer 2020-02-09 11:51:08 +01:00
parent 173ec37bb2
commit f6233ab412
2 changed files with 101 additions and 1 deletions
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2
sysdeps/unix/sysv/linux/Makefile
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@ -274,7 +274,7 @@ sysdep_routines += xstatconv internal_statvfs internal_statvfs64 \
sysdep_headers += bits/fcntl-linux.h
tests += tst-fallocate tst-fallocate64
tests += tst-fallocate tst-fallocate64 tst-o_path-locks
endif
ifeq ($(subdir),elf)

100
sysdeps/unix/sysv/linux/tst-o_path-locks.c Normal file
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@ -0,0 +1,100 @@
/* Test that closing O_PATH descriptors does not release POSIX advisory locks.
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 <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <support/check.h>
#include <support/namespace.h>
#include <support/support.h>
#include <support/temp_file.h>
#include <support/xunistd.h>
/* The subprocess writes the errno value of the lock operation
here. */
static int *shared_errno;
/* The path of the temporary file which is locked. */
static char *path;
/* Try to obtain an exclusive lock on the file at path. */
static void
subprocess (void *closure)
{
int fd = xopen (path, O_RDWR, 0);
struct flock64 lock = { .l_type = F_WRLCK, };
int ret = fcntl64 (fd, F_SETLK, &lock);
if (ret == 0)
*shared_errno = 0;
else
*shared_errno = errno;
xclose (fd);
}
/* Return true if the file at path is currently locked, false if
not. */
static bool
probe_lock (void)
{
*shared_errno = -1;
support_isolate_in_subprocess (subprocess, NULL);
if (*shared_errno == 0)
/* Lock was aquired by the subprocess, so this process has not
locked it. */
return false;
else
{
/* POSIX allows both EACCES and EAGAIN. Linux use EACCES. */
TEST_COMPARE (*shared_errno, EAGAIN);
return true;
}
}
static int
do_test (void)
{
shared_errno = support_shared_allocate (sizeof (*shared_errno));
int fd = create_temp_file ("tst-o_path-locks-", &path);
/* The file is not locked initially. */
TEST_VERIFY (!probe_lock ());
struct flock64 lock = { .l_type = F_WRLCK, };
TEST_COMPARE (fcntl64 (fd, F_SETLK, &lock), 0);
/* The lock has been acquired. */
TEST_VERIFY (probe_lock ());
/* Closing the same file via a different descriptor releases the
lock. */
xclose (xopen (path, O_RDONLY, 0));
TEST_VERIFY (!probe_lock ());
/* But not if it is an O_PATH descriptor. */
TEST_COMPARE (fcntl64 (fd, F_SETLK, &lock), 0);
xclose (xopen (path, O_PATH, 0));
TEST_VERIFY (probe_lock ());
xclose (fd);
free (path);
support_shared_free (shared_errno);
return 0;
}
#include <support/test-driver.c>