Commit 6a75ce16 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

sysctl: Rewrite proc_sys_readdir in terms of first_entry and next_entry 



Replace sysctl_head_next with first_entry and next_entry.  These new
iterators operate at the level of sysctl table entries and filter
out any sysctl tables that should not be shown.

Utilizing two specialized functions instead of a single function removes
conditionals for handling awkward special cases that only come up
at the beginning of iteration, making the iterators easier to read
and understand.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent 076c3eed

fs/proc/proc_sysctl.c

+62 −36
Original line number Diff line number Diff line
@@ -243,31 +243,25 @@ static struct ctl_table *lookup_entry(struct ctl_table_header **phead, 
	return entry;

}



static struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces,

						struct ctl_table_header *prev)

static struct ctl_table_header *next_usable_entry(struct ctl_table *dir,

	struct ctl_table_root *root, struct list_head *tmp)

{

	struct ctl_table_root *root;

	struct nsproxy *namespaces = current->nsproxy;

	struct list_head *header_list;

	struct ctl_table_header *head;

	struct list_head *tmp;



	spin_lock(&sysctl_lock);

	if (prev) {

		head = prev;

		tmp = &prev->ctl_entry;

		unuse_table(prev);

	goto next;

	}

	tmp = &root_table_header.ctl_entry;

	for (;;) {

		head = list_entry(tmp, struct ctl_table_header, ctl_entry);

		root = head->root;



		if (!use_table(head))

		if (head->attached_to != dir ||

		    !head->attached_by->procname ||

		    !use_table(head))

			goto next;

		spin_unlock(&sysctl_lock);



		return head;

	next:

		root = head->root;

		tmp = tmp->next;

		header_list = lookup_header_list(root, namespaces);

		if (tmp != header_list)
@@ -283,13 +277,53 @@ static struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces, 
		tmp = header_list->next;

	}

out:

	spin_unlock(&sysctl_lock);

	return NULL;

}



static struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev)

static void first_entry(

	struct ctl_table_header *dir_head, struct ctl_table *dir,

	struct ctl_table_header **phead, struct ctl_table **pentry)

{

	struct ctl_table_header *head = dir_head;

	struct ctl_table *entry = dir;



	spin_lock(&sysctl_lock);

	if (entry->procname) {

		use_table(head);

	} else {

		head = next_usable_entry(dir, &sysctl_table_root,

					 &sysctl_table_root.default_set.list);

		if (head)

			entry = head->attached_by;

	}

	spin_unlock(&sysctl_lock);

	*phead = head;

	*pentry = entry;

}



static void next_entry(struct ctl_table *dir,

	struct ctl_table_header **phead, struct ctl_table **pentry)

{

	return __sysctl_head_next(current->nsproxy, prev);

	struct ctl_table_header *head = *phead;

	struct ctl_table *entry = *pentry;



	entry++;

	if (!entry->procname) {

		struct ctl_table_root *root = head->root;

		struct list_head *tmp = &head->ctl_entry;

		if (head->attached_to != dir) {

			root = &sysctl_table_root;

			tmp = &sysctl_table_root.default_set.list;

		}

		spin_lock(&sysctl_lock);

		unuse_table(head);

		head = next_usable_entry(dir, root, tmp);

		spin_unlock(&sysctl_lock);

		if (head)

			entry = head->attached_by;

	}

	*phead = head;

	*pentry = entry;

}



void register_sysctl_root(struct ctl_table_root *root)
@@ -533,20 +567,17 @@ static int scan(struct ctl_table_header *head, ctl_table *table, 
		unsigned long *pos, struct file *file,

		void *dirent, filldir_t filldir)

{



	for (; table->procname; table++, (*pos)++) {

	int res;



		if (*pos < file->f_pos)

			continue;

	if ((*pos)++ < file->f_pos)

		return 0;



	res = proc_sys_fill_cache(file, dirent, filldir, head, table);

		if (res)

			return res;



		file->f_pos = *pos + 1;

	}

	return 0;

	if (res == 0)

		file->f_pos = *pos;



	return res;

}



static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
@@ -556,6 +587,7 @@ static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) 
	struct ctl_table_header *head = grab_header(inode);

	struct ctl_table *table = PROC_I(inode)->sysctl_entry;

	struct ctl_table_header *h = NULL;

	struct ctl_table *entry;

	unsigned long pos;

	int ret = -EINVAL;
@@ -585,14 +617,8 @@ static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir) 
	}

	pos = 2;



	ret = scan(head, table, &pos, filp, dirent, filldir);

	if (ret)

		goto out;



	for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {

		if (h->attached_to != table)

			continue;

		ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);

	for (first_entry(head, table, &h, &entry); h; next_entry(table, &h, &entry)) {

		ret = scan(h, entry, &pos, filp, dirent, filldir);

		if (ret) {

			sysctl_head_finish(h);

			break;

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