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Re: [PATCH] login: Fix updwtmp, updwtmx unlocking
- From: Carlos O'Donell <carlos at redhat dot com>
- To: Florian Weimer <fweimer at redhat dot com>, libc-alpha at sourceware dot org
- Date: Wed, 14 Aug 2019 16:10:42 -0400
- Subject: Re: [PATCH] login: Fix updwtmp, updwtmx unlocking
- References: <871rxof0by.fsf@oldenburg2.str.redhat.com>
On 8/14/19 7:33 AM, Florian Weimer wrote:
Commit 5a3afa9738f3dbbaf8c0a35665318c1af782111b (login: Replace
macro-based control flow with function calls in utmp) introduced
a regression because after it, __libc_updwtmp attempts to unlock
the wrong file descriptor.
This makes sense, and it was an easy mistake to make because many
other functions use the same pattern to unlock file_fd.
OK for master if you add a block comment describing the test to the
testsuite.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2019-08-14 Florian Weimer <fweimer@redhat.com>
* login/utmp_file.c (__libc_updwtmp): Unlock the right file
descriptor.
* login/Makefile (tests): Add tst-updwtmpx.
* login/tst-updwtmpx.c: New file.
diff --git a/login/Makefile b/login/Makefile
index 92535f0aec..f9c4264087 100644
--- a/login/Makefile
+++ b/login/Makefile
@@ -43,7 +43,7 @@ endif
subdir-dirs = programs
vpath %.c programs
-tests := tst-utmp tst-utmpx tst-grantpt tst-ptsname tst-getlogin
+tests := tst-utmp tst-utmpx tst-grantpt tst-ptsname tst-getlogin tst-updwtmpx
OK.
# Build the -lutil library with these extra functions.
extra-libs := libutil
diff --git a/login/tst-updwtmpx.c b/login/tst-updwtmpx.c
new file mode 100644
index 0000000000..4eb4a3fbcd
--- /dev/null
+++ b/login/tst-updwtmpx.c
@@ -0,0 +1,108 @@
+/* Basic test coverage for updwtmpx.
OK. Because we broke __libc_updwtmp.
+ Copyright (C) 2019 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; see the file COPYING.LIB. If
+ not, see <http://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/descriptors.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/test-driver.h>
+#include <support/xunistd.h>
+#include <unistd.h>
+#include <utmpx.h>
+
Needs a one paragraph description of the intent of the test.
+static int
+do_test (void)
+{
+ /* Two entries filled with an arbitrary bit pattern. */
+ struct utmpx entries[2];
OK.
+ unsigned char pad;
+ {
+ unsigned char *p = (unsigned char *) &entries[0];
+ for (size_t i = 0; i < sizeof (entries); ++i)
+ {
+ p[i] = i;
+ }
+ /* Make sure that the first and second entry and the padding are
+ different. */
+ p[sizeof (struct utmpx)] = p[0] + 1;
+ pad = p[0] + 2;
+ }
OK.
+
+ char *path;
+ int fd = create_temp_file ("tst-updwtmpx-", &path);
OK.
+
+ /* Used to check that updwtmpx does not leave an open file
+ descriptor around. */
+ struct support_descriptors *descriptors = support_descriptors_list ();
OK.
+
+ /* updwtmpx is expected to remove misalignment. Optionally insert
+ one byte of misalignment at the start and in the middle (after
+ the first entry). */
OK.
+ for (int misaligned_start = 0; misaligned_start < 2; ++misaligned_start)
+ for (int misaligned_middle = 0; misaligned_middle < 2; ++misaligned_middle)
+ {
+ if (test_verbose > 0)
+ printf ("info: misaligned_start=%d misaligned_middle=%d\n",
+ misaligned_start, misaligned_middle);
+
+ xftruncate (fd, 0);
+ TEST_COMPARE (pwrite64 (fd, &pad, misaligned_start, 0),
+ misaligned_start);
+
+ /* Write first entry and check it. */
+ errno = 0;
+ updwtmpx (path, &entries[0]);
+ TEST_COMPARE (errno, 0);
+ support_descriptors_check (descriptors);
+ TEST_COMPARE (xlseek (fd, 0, SEEK_END), sizeof (struct utmpx));
+ struct utmpx buffer;
+ TEST_COMPARE (pread64 (fd, &buffer, sizeof (buffer), 0),
+ sizeof (buffer));
+ TEST_COMPARE_BLOB (&entries[0], sizeof (entries[0]),
+ &buffer, sizeof (buffer));
OK.
+
+ /* Middle mis-alignmet. */
+ TEST_COMPARE (pwrite64 (fd, &pad, misaligned_middle,
+ sizeof (struct utmpx)), misaligned_middle);
+
+ /* Write second entry and check both entries. */
+ errno = 0;
+ updwtmpx (path, &entries[1]);
+ TEST_COMPARE (errno, 0);
+ support_descriptors_check (descriptors);
+ TEST_COMPARE (xlseek (fd, 0, SEEK_END), 2 * sizeof (struct utmpx));
+ TEST_COMPARE (pread64 (fd, &buffer, sizeof (buffer), 0),
+ sizeof (buffer));
+ TEST_COMPARE_BLOB (&entries[0], sizeof (entries[0]),
+ &buffer, sizeof (buffer));
+ TEST_COMPARE (pread64 (fd, &buffer, sizeof (buffer), sizeof (buffer)),
+ sizeof (buffer));
+ TEST_COMPARE_BLOB (&entries[1], sizeof (entries[1]),
+ &buffer, sizeof (buffer));
OK.
+ }
+
+ support_descriptors_free (descriptors);
+ free (path);
+ xclose (fd);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/login/utmp_file.c b/login/utmp_file.c
index 7bd6034af4..5e4e66d1d0 100644
--- a/login/utmp_file.c
+++ b/login/utmp_file.c
@@ -503,7 +503,7 @@ __libc_updwtmp (const char *file, const struct utmp *utmp)
result = 0;
unlock_return:
- file_unlock (file_fd);
+ file_unlock (fd);
OK. Reviewed the surrounding code, and verified that __libc_updwtmp uses 'fd' because
it's what was locked earlier in the function, and that file_fd should not be used
(which is only for setutent/getutent/endutent/getutline... and others which don't
open their own file).
file_lock_restore (&fl);
/* Close WTMP file. */
--
Cheers,
Carlos.