Commit 076c3eed authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

sysctl: Rewrite proc_sys_lookup introducing find_entry and lookup_entry. 



Replace the helpers that proc_sys_lookup uses with helpers that work
in terms of an entire sysctl directory.  This is worse for sysctl_lock
hold times but it is much better for code clarity and the code cleanups
to come.

find_in_table is no longer needed so it is removed.

find_entry a general helper to find entries in a directory is added.

lookup_entry is a simple wrapper around find_entry that takes the
sysctl_lock increases the use count if an entry is found and drops
the sysctl_lock.

Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
parent a194558e

fs/proc/proc_sysctl.c

+76 −26
Original line number Diff line number Diff line
@@ -49,6 +49,55 @@ static struct ctl_table_root sysctl_table_root = { 


static DEFINE_SPINLOCK(sysctl_lock);



static int namecmp(const char *name1, int len1, const char *name2, int len2)

{

	int minlen;

	int cmp;



	minlen = len1;

	if (minlen > len2)

		minlen = len2;



	cmp = memcmp(name1, name2, minlen);

	if (cmp == 0)

		cmp = len1 - len2;

	return cmp;

}



static struct ctl_table *find_entry(struct ctl_table_header **phead,

	struct ctl_table_set *set,

	struct ctl_table_header *dir_head, struct ctl_table *dir,

	const char *name, int namelen)

{

	struct ctl_table_header *head;

	struct ctl_table *entry;



	if (dir_head->set == set) {

		for (entry = dir; entry->procname; entry++) {

			const char *procname = entry->procname;

			if (namecmp(procname, strlen(procname), name, namelen) == 0) {

				*phead = dir_head;

				return entry;

			}

		}

	}



	list_for_each_entry(head, &set->list, ctl_entry) {

		if (head->unregistering)

			continue;

		if (head->attached_to != dir)

			continue;

		for (entry = head->attached_by; entry->procname; entry++) {

			const char *procname = entry->procname;

			if (namecmp(procname, strlen(procname), name, namelen) == 0) {

				*phead = head;

				return entry;

			}

		}

	}

	return NULL;

}



static void init_header(struct ctl_table_header *head,

	struct ctl_table_root *root, struct ctl_table_set *set,

	struct ctl_table *table)
@@ -168,6 +217,32 @@ lookup_header_list(struct ctl_table_root *root, struct nsproxy *namespaces) 
	return &set->list;

}



static struct ctl_table *lookup_entry(struct ctl_table_header **phead,

				      struct ctl_table_header *dir_head,

				      struct ctl_table *dir,

				      const char *name, int namelen)

{

	struct ctl_table_header *head;

	struct ctl_table *entry;

	struct ctl_table_root *root;

	struct ctl_table_set *set;



	spin_lock(&sysctl_lock);

	root = &sysctl_table_root;

	do {

		set = lookup_header_set(root, current->nsproxy);

		entry = find_entry(&head, set, dir_head, dir, name, namelen);

		if (entry && use_table(head))

			*phead = head;

		else

			entry = NULL;

		root = list_entry(root->root_list.next,

				  struct ctl_table_root, root_list);

	} while (!entry && root != &sysctl_table_root);

	spin_unlock(&sysctl_lock);

	return entry;

}



static struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces,

						struct ctl_table_header *prev)

{
@@ -284,21 +359,6 @@ out: 
	return inode;

}



static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)

{

	for ( ; p->procname; p++) {

		if (strlen(p->procname) != name->len)

			continue;



		if (memcmp(p->procname, name->name, name->len) != 0)

			continue;



		/* I have a match */

		return p;

	}

	return NULL;

}



static struct ctl_table_header *grab_header(struct inode *inode)

{

	struct ctl_table_header *head = PROC_I(inode)->sysctl;
@@ -328,17 +388,7 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry, 


	table = table ? table->child : &head->ctl_table[1];



	p = find_in_table(table, name);

	if (!p) {

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

			if (h->attached_to != table)

				continue;

			p = find_in_table(h->attached_by, name);

			if (p)

				break;

		}

	}



	p = lookup_entry(&h, head, table, name->name, name->len);

	if (!p)

		goto out;

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