diff mbox series

[v3,5/5] selftests: add fchmodat4(2) selftest

Message ID c3606ec38227d921fa8a3e11613ffdb2f3ea7636.1689074739.git.legion@kernel.org (mailing list archive)
State Handled Elsewhere
Headers show
Series [v3,1/5] Non-functional cleanup of a "__user * filename" | expand

Commit Message

Alexey Gladkov July 11, 2023, 11:25 a.m. UTC 
The test marks as skipped if a syscall with the AT_SYMLINK_NOFOLLOW flag
fails. This is because not all filesystems support changing the mode
bits of symlinks properly. These filesystems return an error but change
the mode bits:

newfstatat(4, "regfile", {st_mode=S_IFREG|0640, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0
newfstatat(4, "symlink", {st_mode=S_IFLNK|0777, st_size=7, ...}, AT_SYMLINK_NOFOLLOW) = 0
syscall_0x1c3(0x4, 0x55fa1f244396, 0x180, 0x100, 0x55fa1f24438e, 0x34) = -1 EOPNOTSUPP (Operation not supported)
newfstatat(4, "regfile", {st_mode=S_IFREG|0640, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0

This happens with btrfs and xfs:

 $ /kernel/tools/testing/selftests/fchmodat4/fchmodat4_test
 TAP version 13
 1..1
 ok 1 # SKIP fchmodat4(symlink)
 # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0

 $ stat /tmp/ksft-fchmodat4.*/symlink
   File: /tmp/ksft-fchmodat4.3NCqlE/symlink -> regfile
   Size: 7               Blocks: 0          IO Block: 4096   symbolic link
 Device: 7,0     Inode: 133         Links: 1
 Access: (0600/lrw-------)  Uid: (    0/    root)   Gid: (    0/    root)

Signed-off-by: Alexey Gladkov <legion@kernel.org>
---
 tools/testing/selftests/Makefile              |   1 +
 tools/testing/selftests/fchmodat4/.gitignore  |   2 +
 tools/testing/selftests/fchmodat4/Makefile    |   6 +
 .../selftests/fchmodat4/fchmodat4_test.c      | 151 ++++++++++++++++++
 4 files changed, 160 insertions(+)
 create mode 100644 tools/testing/selftests/fchmodat4/.gitignore
 create mode 100644 tools/testing/selftests/fchmodat4/Makefile
 create mode 100644 tools/testing/selftests/fchmodat4/fchmodat4_test.c

Comments

Florian Weimer July 11, 2023, 12:10 p.m. UTC | #1 
* Alexey Gladkov:

> The test marks as skipped if a syscall with the AT_SYMLINK_NOFOLLOW flag
> fails. This is because not all filesystems support changing the mode
> bits of symlinks properly. These filesystems return an error but change
> the mode bits:
>
> newfstatat(4, "regfile", {st_mode=S_IFREG|0640, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0
> newfstatat(4, "symlink", {st_mode=S_IFLNK|0777, st_size=7, ...}, AT_SYMLINK_NOFOLLOW) = 0
> syscall_0x1c3(0x4, 0x55fa1f244396, 0x180, 0x100, 0x55fa1f24438e, 0x34) = -1 EOPNOTSUPP (Operation not supported)
> newfstatat(4, "regfile", {st_mode=S_IFREG|0640, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0
>
> This happens with btrfs and xfs:
>
>  $ /kernel/tools/testing/selftests/fchmodat4/fchmodat4_test
>  TAP version 13
>  1..1
>  ok 1 # SKIP fchmodat4(symlink)
>  # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
>
>  $ stat /tmp/ksft-fchmodat4.*/symlink
>    File: /tmp/ksft-fchmodat4.3NCqlE/symlink -> regfile
>    Size: 7               Blocks: 0          IO Block: 4096   symbolic link
>  Device: 7,0     Inode: 133         Links: 1
>  Access: (0600/lrw-------)  Uid: (    0/    root)   Gid: (    0/    root)
>
> Signed-off-by: Alexey Gladkov <legion@kernel.org>

This looks like a bug in those file systems?

As an extra test, “echo 3 > /proc/sys/vm/drop_caches” sometimes has
strange effects in such cases because the bits are not actually stored
on disk, only in the dentry cache.

Thanks,
Florian
Alexey Gladkov July 11, 2023, 1:38 p.m. UTC | #2 
On Tue, Jul 11, 2023 at 02:10:58PM +0200, Florian Weimer wrote:
> * Alexey Gladkov:
> 
> > The test marks as skipped if a syscall with the AT_SYMLINK_NOFOLLOW flag
> > fails. This is because not all filesystems support changing the mode
> > bits of symlinks properly. These filesystems return an error but change
> > the mode bits:
> >
> > newfstatat(4, "regfile", {st_mode=S_IFREG|0640, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0
> > newfstatat(4, "symlink", {st_mode=S_IFLNK|0777, st_size=7, ...}, AT_SYMLINK_NOFOLLOW) = 0
> > syscall_0x1c3(0x4, 0x55fa1f244396, 0x180, 0x100, 0x55fa1f24438e, 0x34) = -1 EOPNOTSUPP (Operation not supported)
> > newfstatat(4, "regfile", {st_mode=S_IFREG|0640, st_size=0, ...}, AT_SYMLINK_NOFOLLOW) = 0
> >
> > This happens with btrfs and xfs:
> >
> >  $ /kernel/tools/testing/selftests/fchmodat4/fchmodat4_test
> >  TAP version 13
> >  1..1
> >  ok 1 # SKIP fchmodat4(symlink)
> >  # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
> >
> >  $ stat /tmp/ksft-fchmodat4.*/symlink
> >    File: /tmp/ksft-fchmodat4.3NCqlE/symlink -> regfile
> >    Size: 7               Blocks: 0          IO Block: 4096   symbolic link
> >  Device: 7,0     Inode: 133         Links: 1
> >  Access: (0600/lrw-------)  Uid: (    0/    root)   Gid: (    0/    root)
> >
> > Signed-off-by: Alexey Gladkov <legion@kernel.org>
> 
> This looks like a bug in those file systems?

To me this looks like a bug. I'm fine if the operation ends with
EOPNOTSUPP, but in that case the mode bits shouldn't change.

> As an extra test, “echo 3 > /proc/sys/vm/drop_caches” sometimes has
> strange effects in such cases because the bits are not actually stored
> on disk, only in the dentry cache.

tmpfs
syscall_0x1c3(0xffffff9c, 0x7ffd58758574, 0, 0x100, 0x7f6cf18adc70, 0x7ffd58756ad8) = 0
+++ exited with 0 +++
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f
=== dropping caches ===
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f

ext4
syscall_0x1c3(0xffffff9c, 0x7ffedfdb4574, 0, 0x100, 0x7f7f40b45c70, 0x7ffedfdb3ae8) = -1 EOPNOTSUPP (Operation not supported)
+++ exited with 1 +++
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f
=== dropping caches ===
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f

xfs
syscall_0x1c3(0xffffff9c, 0x7ffcd03ce574, 0, 0x100, 0x7ff2f2980c70, 0x7ffcd03cdd38) = -1 EOPNOTSUPP (Operation not supported)
+++ exited with 1 +++
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f
=== dropping caches ===
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f

btrfs
syscall_0x1c3(0xffffff9c, 0x7fff13d2e574, 0, 0x100, 0x7f9b67f59c70, 0x7fff13d2ca88) = -1 EOPNOTSUPP (Operation not supported)
+++ exited with 1 +++
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f
=== dropping caches ===
l--------- 1 root root 1 Jul 11 16:36 /tmp/dir/link -> f

reiserfs
syscall_0x1c3(0xffffff9c, 0x7ffdf75af574, 0, 0x100, 0x7f7ad0634c70, 0x7ffdf75ae478) = 0
+++ exited with 0 +++
l--------- 1 root root 1 Jul 11 16:43 /tmp/dir/link -> f
=== dropping caches ===
l--------- 1 root root 1 Jul 11 16:43 /tmp/dir/link -> f
diff mbox series

Patch

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 90a62cf75008..fe61fa55412d 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -17,6 +17,7 @@  TARGETS += drivers/net/bonding
 TARGETS += drivers/net/team
 TARGETS += efivarfs
 TARGETS += exec
+TARGETS += fchmodat4
 TARGETS += filesystems
 TARGETS += filesystems/binderfs
 TARGETS += filesystems/epoll
diff --git a/tools/testing/selftests/fchmodat4/.gitignore b/tools/testing/selftests/fchmodat4/.gitignore
new file mode 100644
index 000000000000..82a4846cbc4b
--- /dev/null
+++ b/tools/testing/selftests/fchmodat4/.gitignore
@@ -0,0 +1,2 @@ 
+# SPDX-License-Identifier: GPL-2.0-only
+/*_test
diff --git a/tools/testing/selftests/fchmodat4/Makefile b/tools/testing/selftests/fchmodat4/Makefile
new file mode 100644
index 000000000000..3d38a69c3c12
--- /dev/null
+++ b/tools/testing/selftests/fchmodat4/Makefile
@@ -0,0 +1,6 @@ 
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+CFLAGS += -Wall -O2 -g -fsanitize=address -fsanitize=undefined
+TEST_GEN_PROGS := fchmodat4_test
+
+include ../lib.mk
diff --git a/tools/testing/selftests/fchmodat4/fchmodat4_test.c b/tools/testing/selftests/fchmodat4/fchmodat4_test.c
new file mode 100644
index 000000000000..50beb731d8ba
--- /dev/null
+++ b/tools/testing/selftests/fchmodat4/fchmodat4_test.c
@@ -0,0 +1,151 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#define _GNU_SOURCE
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <syscall.h>
+#include <unistd.h>
+
+#include "../kselftest.h"
+
+#ifndef __NR_fchmodat4
+	#if defined __alpha__
+		#define __NR_fchmodat4 561
+	#elif defined _MIPS_SIM
+		#if _MIPS_SIM == _MIPS_SIM_ABI32	/* o32 */
+			#define __NR_fchmodat4 (451 + 4000)
+		#endif
+		#if _MIPS_SIM == _MIPS_SIM_NABI32	/* n32 */
+			#define __NR_fchmodat4 (451 + 6000)
+		#endif
+		#if _MIPS_SIM == _MIPS_SIM_ABI64	/* n64 */
+			#define __NR_fchmodat4 (451 + 5000)
+		#endif
+	#elif defined __ia64__
+		#define __NR_fchmodat4 (451 + 1024)
+	#else
+		#define __NR_fchmodat4 451
+	#endif
+#endif
+
+int sys_fchmodat4(int dfd, const char *filename, mode_t mode, int flags)
+{
+	int ret = syscall(__NR_fchmodat4, dfd, filename, mode, flags);
+	return ret >= 0 ? ret : -errno;
+}
+
+int setup_testdir(void)
+{
+	int dfd, ret;
+	char dirname[] = "/tmp/ksft-fchmodat4.XXXXXX";
+
+	/* Make the top-level directory. */
+	if (!mkdtemp(dirname))
+		ksft_exit_fail_msg("setup_testdir: failed to create tmpdir\n");
+
+	dfd = open(dirname, O_PATH | O_DIRECTORY);
+	if (dfd < 0)
+		ksft_exit_fail_msg("setup_testdir: failed to open tmpdir\n");
+
+	ret = openat(dfd, "regfile", O_CREAT | O_WRONLY | O_TRUNC, 0644);
+	if (ret < 0)
+		ksft_exit_fail_msg("setup_testdir: failed to create file in tmpdir\n");
+	close(ret);
+
+	ret = symlinkat("regfile", dfd, "symlink");
+	if (ret < 0)
+		ksft_exit_fail_msg("setup_testdir: failed to create symlink in tmpdir\n");
+
+	return dfd;
+}
+
+int expect_mode(int dfd, const char *filename, mode_t expect_mode)
+{
+	struct stat st;
+	int ret = fstatat(dfd, filename, &st, AT_SYMLINK_NOFOLLOW);
+
+	if (ret)
+		ksft_exit_fail_msg("expect_mode: %s: fstatat failed\n", filename);
+
+	return (st.st_mode == expect_mode);
+}
+
+void test_regfile(void)
+{
+	int dfd, ret;
+
+	dfd = setup_testdir();
+
+	ret = sys_fchmodat4(dfd, "regfile", 0640, 0);
+
+	if (ret < 0)
+		ksft_exit_fail_msg("test_regfile: fchmodat4(noflag) failed\n");
+
+	if (!expect_mode(dfd, "regfile", 0100640))
+		ksft_exit_fail_msg("test_regfile: wrong file mode bits after fchmodat4\n");
+
+	ret = sys_fchmodat4(dfd, "regfile", 0600, AT_SYMLINK_NOFOLLOW);
+
+	if (ret < 0)
+		ksft_exit_fail_msg("test_regfile: fchmodat4(AT_SYMLINK_NOFOLLOW) failed\n");
+
+	if (!expect_mode(dfd, "regfile", 0100600))
+		ksft_exit_fail_msg("test_regfile: wrong file mode bits after fchmodat4 with nofollow\n");
+
+	ksft_test_result_pass("fchmodat4(regfile)\n");
+}
+
+void test_symlink(void)
+{
+	int dfd, ret;
+
+	dfd = setup_testdir();
+
+	ret = sys_fchmodat4(dfd, "symlink", 0640, 0);
+
+	if (ret < 0)
+		ksft_exit_fail_msg("test_symlink: fchmodat4(noflag) failed\n");
+
+	if (!expect_mode(dfd, "regfile", 0100640))
+		ksft_exit_fail_msg("test_symlink: wrong file mode bits after fchmodat4\n");
+
+	if (!expect_mode(dfd, "symlink", 0120777))
+		ksft_exit_fail_msg("test_symlink: wrong symlink mode bits after fchmodat4\n");
+
+	ret = sys_fchmodat4(dfd, "symlink", 0600, AT_SYMLINK_NOFOLLOW);
+
+	/*
+	 * On certain filesystems (xfs or btrfs), chmod operation fails. So we
+	 * first check the symlink target but if the operation fails we mark the
+	 * test as skipped.
+	 *
+	 * https://sourceware.org/legacy-ml/libc-alpha/2020-02/msg00467.html
+	 */
+	if (ret == 0 && !expect_mode(dfd, "symlink", 0120600))
+		ksft_exit_fail_msg("test_symlink: wrong symlink mode bits after fchmodat4 with nofollow\n");
+
+	if (!expect_mode(dfd, "regfile", 0100640))
+		ksft_exit_fail_msg("test_symlink: wrong file mode bits after fchmodat4 with nofollow\n");
+
+	if (ret != 0)
+		ksft_test_result_skip("fchmodat4(symlink)\n");
+	else
+		ksft_test_result_pass("fchmodat4(symlink)\n");
+}
+
+#define NUM_TESTS 2
+
+int main(int argc, char **argv)
+{
+	ksft_print_header();
+	ksft_set_plan(NUM_TESTS);
+
+	test_regfile();
+	test_symlink();
+
+	if (ksft_get_fail_cnt() + ksft_get_error_cnt() > 0)
+		ksft_exit_fail();
+	else
+		ksft_exit_pass();
+}