Re: [PATCH v2 2/2] vfs: Add new setgid_create_acl test

["xuyang2018.jy@fujitsu.com" <xuyang2018.jy@fujitsu.com>]

on 2022/08/29 21:52, Christian Brauner wrote:
> On Tue, Jul 26, 2022 at 05:31:21PM +0800, Yang Xu wrote:
>> The current_umask() is stripped from the mode directly in the vfs if the
>> filesystem either doesn't support acls or the filesystem has been
>> mounted without posic acl support.
>>
>> If the filesystem does support acls then current_umask() stripping is
>> deferred to posix_acl_create(). So when the filesystem calls
>> posix_acl_create() and there are no acls set or not supported then
>> current_umask() will be stripped.
>>
>> If the parent directory has a default acl then permissions are based off
>> of that and current_umask() is ignored. Specifically, if the ACL has an
>> ACL_MASK entry, the group permissions correspond to the permissions of
>> the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
>> group permissions correspond to the permissions of the ACL_GROUP_OBJ
>> entry.
>>
>> Here we only use setfacl to set default acl or add ACL_MASK to check
>> whether inode strip  S_ISGID works correctly.
>>
>> Like umask test, this patch is also designed to test kernel patchset behaviour
>> "move S_ISGID stripping into the vfs* helper"
>>
>> Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
>> ---
> 
> Hey Yang,
> 
> Thank your for all that work! Just a few nits.
> 
>> 1.add kernel commit id
>> 2.move umask into parent process intead of child process
>> 3.remove duplicated comment for ACL_GROUP_OBJ and ACL_MASK because
>> we have mentioned it before the function
>>   src/vfs/idmapped-mounts.c | 704 ++++++++++++++++++++++++++++++++++++++
>>   src/vfs/idmapped-mounts.h |   1 +
>>   src/vfs/vfstest.c         | 345 ++++++++++++++++++-
>>   tests/generic/999         |  33 ++
>>   tests/generic/999.out     |   2 +
>>   5 files changed, 1084 insertions(+), 1 deletion(-)
>>   create mode 100755 tests/generic/999
>>   create mode 100644 tests/generic/999.out
>>
>> diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c
>> index f63ac44b..f934cf4a 100644
>> --- a/src/vfs/idmapped-mounts.c
>> +++ b/src/vfs/idmapped-mounts.c
>> @@ -8083,6 +8083,700 @@ out:
>>   	return fret;
>>   }
>>   
>> +static int setgid_create_acl_idmapped(const struct vfstest_info *info)
>> +{
>> +	int fret = -1;
>> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
>> +	struct mount_attr attr = {
>> +		.attr_set = MOUNT_ATTR_IDMAP,
>> +	};
>> +	pid_t pid;
>> +	int tmpfile_fd = -EBADF;
>> +	bool supported = false;
>> +	char path[PATH_MAX];
>> +	mode_t mode;
>> +
>> +	if (!caps_supported())
>> +		return 0;
>> +
>> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
>> +			      S_IWUSR |
>> +			      S_IRGRP |
>> +			      S_IWGRP |
>> +			      S_IROTH |
>> +			      S_IWOTH |
>> +			      S_IXUSR |
>> +			      S_IXGRP |
>> +			      S_IXOTH |
>> +			      S_ISGID), 0) {
>> +		log_stderr("failure: fchmod");
>> +		goto out;
>> +	}
>> +
>> +	/* Verify that the sid bits got raised. */
>> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
>> +		log_stderr("failure: is_setgid");
>> +		goto out;
>> +	}
>> +
>> +	/* Changing mount properties on a detached mount. */
>> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
>> +	if (attr.userns_fd < 0) {
>> +		log_stderr("failure: get_userns_fd");
>> +		goto out;
>> +	}
>> +
>> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
>> +				     AT_EMPTY_PATH |
>> +				     AT_NO_AUTOMOUNT |
>> +				     AT_SYMLINK_NOFOLLOW |
>> +				     OPEN_TREE_CLOEXEC |
>> +				     OPEN_TREE_CLONE);
>> +	if (open_tree_fd < 0) {
>> +		log_stderr("failure: sys_open_tree");
>> +		goto out;
>> +	}
>> +
>> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
>> +		log_stderr("failure: sys_mount_setattr");
>> +		goto out;
>> +	}
>> +
>> +	supported = openat_tmpfile_supported(open_tree_fd);
>> +
>> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
>> +	 * whether has group execute or search permission.
>> +	 */
>> +	umask(S_IXGRP);
>> +	mode = umask(S_IXGRP);
>> +	if (!(mode & S_IXGRP))
>> +		die("failure: umask");
> 
> Please move all the umask() calls after the fork() into the child.

OK.
> 
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_MASK entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!switch_ids(10000, 11000))
>> +			die("failure: switch fsids");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE2, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_GROUP_OBJ entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!switch_ids(10000, 11000))
>> +			die("failure: switch fsids");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE2, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 10000, not by gid 11000.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 10000, 10000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (!is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 10000, 10000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	fret = 0;
>> +	log_debug("Ran test");
>> +out:
>> +	safe_close(attr.userns_fd);
>> +	safe_close(file1_fd);
>> +	safe_close(open_tree_fd);
>> +
>> +	return fret;
>> +}
>> +
>> +static int setgid_create_acl_idmapped_in_userns(const struct vfstest_info *info)
>> +{
>> +	int fret = -1;
>> +	int file1_fd = -EBADF, open_tree_fd = -EBADF;
>> +	struct mount_attr attr = {
>> +		.attr_set = MOUNT_ATTR_IDMAP,
>> +	};
>> +	pid_t pid;
>> +	int tmpfile_fd = -EBADF;
>> +	bool supported = false;
>> +	char path[PATH_MAX];
>> +	mode_t mode;
>> +
>> +	if (!caps_supported())
>> +		return 0;
>> +
>> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
>> +			      S_IWUSR |
>> +			      S_IRGRP |
>> +			      S_IWGRP |
>> +			      S_IROTH |
>> +			      S_IWOTH |
>> +			      S_IXUSR |
>> +			      S_IXGRP |
>> +			      S_IXOTH |
>> +			      S_ISGID), 0) {
>> +		log_stderr("failure: fchmod");
>> +		goto out;
>> +	}
>> +
>> +	/* Verify that the sid bits got raised. */
>> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
>> +		log_stderr("failure: is_setgid");
>> +		goto out;
>> +	}
>> +
>> +	/* Changing mount properties on a detached mount. */
>> +	attr.userns_fd	= get_userns_fd(0, 10000, 10000);
>> +	if (attr.userns_fd < 0) {
>> +		log_stderr("failure: get_userns_fd");
>> +		goto out;
>> +	}
>> +
>> +	open_tree_fd = sys_open_tree(info->t_dir1_fd, "",
>> +				     AT_EMPTY_PATH |
>> +				     AT_NO_AUTOMOUNT |
>> +				     AT_SYMLINK_NOFOLLOW |
>> +				     OPEN_TREE_CLOEXEC |
>> +				     OPEN_TREE_CLONE);
>> +	if (open_tree_fd < 0) {
>> +		log_stderr("failure: sys_open_tree");
>> +		goto out;
>> +	}
>> +
>> +	if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
>> +		log_stderr("failure: sys_mount_setattr");
>> +		goto out;
>> +	}
>> +
>> +	supported = openat_tmpfile_supported(open_tree_fd);
>> +
>> +	/* Only umask with S_IXGRP because inode strip S_ISGID will check mode
>> +	 * whether has group execute or search permission.
>> +	 */
>> +	umask(S_IXGRP);
>> +	mode = umask(S_IXGRP);
>> +	if (!(mode & S_IXGRP))
>> +		die("failure: umask");
>> +
>> +	/*
>> +	 * Below we verify that setgid inheritance for a newly created file or
>> +	 * directory works correctly. As part of this we need to verify that
>> +	 * newly created files or directories inherit their gid from their
>> +	 * parent directory. So we change the parent directorie's gid to 1000
>> +	 * and create a file with fs{g,u}id 0 and verify that the newly created
>> +	 * file and directory inherit gid 1000, not 0.
>> +	 */
>> +	if (fchownat(info->t_dir1_fd, "", -1, 1000, AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) {
>> +		log_stderr("failure: fchownat");
>> +		goto out;
>> +	}
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_MASK entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!caps_supported()) {
>> +			log_debug("skip: capability library not installed");
>> +			exit(EXIT_SUCCESS);
>> +		}
>> +
>> +		if (!switch_userns(attr.userns_fd, 0, 0, false))
>> +			die("failure: switch_userns");
>> +
>> +		if (!caps_down_fsetid())
>> +			die("failure: caps_down_fsetid");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, FILE2, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_GROUP_OBJ entry.
>> +		 */
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rwx,o::rwx, %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
>> +
>> +		if (!caps_supported()) {
>> +			log_debug("skip: capability library not installed");
>> +			exit(EXIT_SUCCESS);
>> +		}
>> +
>> +		if (!switch_userns(attr.userns_fd, 0, 0, false))
>> +			die("failure: switch_userns");
>> +
>> +		if (!caps_down_fsetid())
>> +			die("failure: caps_down_fsetid");
>> +
>> +		/* create regular file via open() */
>> +		file1_fd = openat(open_tree_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, S_IXGRP | S_ISGID);
>> +		if (file1_fd < 0)
>> +			die("failure: create");
>> +
>> +		/* Neither in_group_p() nor capable_wrt_inode_uidgid() so setgid
>> +		 * bit needs to be stripped.
>> +		 */
>> +		if (is_setgid(open_tree_fd, FILE1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create directory */
>> +		if (mkdirat(open_tree_fd, DIR1, 0000))
>> +			die("failure: create");
>> +
>> +		if (xfs_irix_sgid_inherit_enabled(info->t_fstype)) {
>> +			/* We're not in_group_p(). */
>> +			if (is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		} else {
>> +			/* Directories always inherit the setgid bit. */
>> +			if (!is_setgid(open_tree_fd, DIR1, 0))
>> +				die("failure: is_setgid");
>> +		}
>> +
>> +		if (is_ixgrp(open_tree_fd, DIR1, 0))
>> +			die("failure: is_ixgrp");
>> +
>> +		/* create a special file via mknodat() vfs_create */
>> +		if (mknodat(open_tree_fd, FILE2, S_IFREG | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, FILE2, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, FILE2, 0))
>> +			 die("failure: is_ixgrp");
>> +		/* create a whiteout device via mknodat() vfs_mknod */
>> +		if (mknodat(open_tree_fd, CHRDEV1, S_IFCHR | S_ISGID | S_IXGRP, 0))
>> +			die("failure: mknodat");
>> +
>> +		if (is_setgid(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: is_setgid");
>> +
>> +		if (!is_ixgrp(open_tree_fd, CHRDEV1, 0))
>> +			 die("failure: is_ixgrp");
>> +
>> +		/*
>> +		 * In setgid directories newly created files always inherit the
>> +		 * gid from the parent directory. Verify that the file is owned
>> +		 * by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, FILE1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		/*
>> +		 * In setgid directories newly created directories always
>> +		 * inherit the gid from the parent directory. Verify that the
>> +		 * directory is owned by gid 1000, not by gid 0.
>> +		 */
>> +		if (!expected_uid_gid(open_tree_fd, DIR1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, FILE2, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (!expected_uid_gid(open_tree_fd, CHRDEV1, 0, 0, 1000))
>> +			die("failure: check ownership");
>> +
>> +		if (unlinkat(open_tree_fd, FILE1, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, DIR1, AT_REMOVEDIR))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, FILE2, 0))
>> +			die("failure: delete");
>> +
>> +		if (unlinkat(open_tree_fd, CHRDEV1, 0))
>> +			die("failure: delete");
>> +
>> +		/* create tmpfile via filesystem tmpfile api */
>> +		if (supported) {
>> +			tmpfile_fd = openat(open_tree_fd, ".", O_TMPFILE | O_RDWR, S_IXGRP | S_ISGID);
>> +			if (tmpfile_fd < 0)
>> +				die("failure: create");
>> +			/* link the temporary file into the filesystem, making it permanent */
>> +			snprintf(path, PATH_MAX,  "/proc/self/fd/%d", tmpfile_fd);
>> +			if (linkat(AT_FDCWD, path, open_tree_fd, FILE3, AT_SYMLINK_FOLLOW))
>> +				die("failure: linkat");
>> +			if (close(tmpfile_fd))
>> +				die("failure: close");
>> +			if (is_setgid(open_tree_fd, FILE3, 0))
>> +				die("failure: is_setgid");
>> +			if (!is_ixgrp(open_tree_fd, FILE3, 0))
>> +				die("failure: is_ixgrp");
>> +			if (!expected_uid_gid(open_tree_fd, FILE3, 0, 0, 1000))
>> +				die("failure: check ownership");
>> +			if (unlinkat(open_tree_fd, FILE3, 0))
>> +				die("failure: delete");
>> +		}
>> +
>> +		exit(EXIT_SUCCESS);
>> +	}
>> +	if (wait_for_pid(pid))
>> +		goto out;
>> +
>> +	fret = 0;
>> +	log_debug("Ran test");
>> +out:
>> +	safe_close(attr.userns_fd);
>> +	safe_close(file1_fd);
>> +	safe_close(open_tree_fd);
>> +
>> +	return fret;
>> +}
>> +
>>   static const struct test_struct t_idmapped_mounts[] = {
>>   	{ acls,                                                         true,   "posix acls on regular mounts",                                                                 },
>>   	{ create_in_userns,                                             true,   "create operations in user namespace",                                                          },
>> @@ -8174,3 +8868,13 @@ const struct test_suite s_setgid_create_umask_idmapped_mounts = {
>>   	.tests = t_setgid_create_umask_idmapped_mounts,
>>   	.nr_tests = ARRAY_SIZE(t_setgid_create_umask_idmapped_mounts),
>>   };
>> +
>> +static const struct test_struct t_setgid_create_acl_idmapped_mounts[] = {
>> +	{ setgid_create_acl_idmapped,					T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount",                },
>> +	{ setgid_create_acl_idmapped_in_userns,				T_REQUIRE_IDMAPPED_MOUNTS,	"create operations by using acl in directories with setgid bit set on idmapped mount inside userns",  },
>> +};
>> +
>> +const struct test_suite s_setgid_create_acl_idmapped_mounts = {
>> +	.tests = t_setgid_create_acl_idmapped_mounts,
>> +	.nr_tests = ARRAY_SIZE(t_setgid_create_acl_idmapped_mounts),
>> +};
>> diff --git a/src/vfs/idmapped-mounts.h b/src/vfs/idmapped-mounts.h
>> index a9fb31ea..3b0f0825 100644
>> --- a/src/vfs/idmapped-mounts.h
>> +++ b/src/vfs/idmapped-mounts.h
>> @@ -15,5 +15,6 @@ extern const struct test_suite s_nested_userns;
>>   extern const struct test_suite s_setattr_fix_968219708108;
>>   extern const struct test_suite s_setxattr_fix_705191b03d50;
>>   extern const struct test_suite s_setgid_create_umask_idmapped_mounts;
>> +extern const struct test_suite s_setgid_create_acl_idmapped_mounts;
>>   
>>   #endif /* __IDMAPPED_MOUNTS_H */
>> diff --git a/src/vfs/vfstest.c b/src/vfs/vfstest.c
>> index e928a1f5..f7639de3 100644
>> --- a/src/vfs/vfstest.c
>> +++ b/src/vfs/vfstest.c
>> @@ -27,6 +27,8 @@
>>   #include "missing.h"
>>   #include "utils.h"
>>   
>> +static char t_buf[PATH_MAX];
>> +
>>   static void init_vfstest_info(struct vfstest_info *info)
>>   {
>>   	info->t_overflowuid		= 65534;
>> @@ -1913,6 +1915,325 @@ out:
>>   	return fret;
>>   }
>>   
>> +/*
>> + * If the parent directory has a default acl then permissions are based off
>> + * of that and current_umask() is ignored. Specifically, if the ACL has an
>> + * ACL_MASK entry, the group permissions correspond to the permissions of
>> + * the ACL_MASK entry. Otherwise, if the ACL has no ACL_MASK entry, the
>> + * group permissions correspond to the permissions of the ACL_GROUP_OBJ
>> + * entry.
>> + *
>> + * Use setfacl to check whether inode strip S_ISGID works correctly.
>> + *
>> + * Test for commit
>> + * 1639a49ccdce ("fs: move S_ISGID stripping into the vfs_*() helpers").
>> + */
> 
> This comment is pretty helpful and I'd like to see similar ones on top
> of all the other tests you're adding. That would make it easier for
> other to understand what's going on.

OK.
> 
>> +
>> +static int setgid_create_acl(const struct vfstest_info *info)
>> +{
>> +	int fret = -1;
>> +	int file1_fd = -EBADF;
>> +	int tmpfile_fd = -EBADF;
>> +	pid_t pid;
>> +	bool supported = false;
>> +	mode_t mode;
>> +
>> +	if (!caps_supported())
>> +		return 0;
>> +
>> +	if (fchmod(info->t_dir1_fd, S_IRUSR |
>> +			      S_IWUSR |
>> +			      S_IRGRP |
>> +			      S_IWGRP |
>> +			      S_IROTH |
>> +			      S_IWOTH |
>> +			      S_IXUSR |
>> +			      S_IXGRP |
>> +			      S_IXOTH |
>> +			      S_ISGID), 0) {
>> +		log_stderr("failure: fchmod");
>> +		goto out;
>> +	}
>> +
>> +	/* Verify that the setgid bit got raised. */
>> +	if (!is_setgid(info->t_dir1_fd, "", AT_EMPTY_PATH)) {
>> +		log_stderr("failure: is_setgid");
>> +		goto out;
>> +	}
>> +
>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>> +
>> +	umask(S_IXGRP);
>> +	mode = umask(S_IXGRP);
>> +	if (!(mode & S_IXGRP))
>> +		die("failure: umask");
>> +
>> +	pid = fork();
>> +	if (pid < 0) {
>> +		log_stderr("failure: fork");
>> +		goto out;
>> +	}
>> +	if (pid == 0) {
>> +		/* The group permissions correspond to the permissions of the
>> +		 * ACL_MASK entry.
>> +		 */
> 
> It wouldn't hurt to add a longer comment to these setfacl calls
> detailing what you're trying to test exactly otherwise it may be hard
> for other who are not familiar with ACLs what this does. :)

Yes, will add a longer comment.

Best Regards
Yang Xu
> 
>> +		snprintf(t_buf, sizeof(t_buf), "setfacl -d -m u::rwx,g::rw,o::rwx,m:rw %s/%s", info->t_mountpoint, T_DIR1);
>> +		if (system(t_buf))
>> +			die("failure: system");
> 
> Other than that this looks good!
> Christian