1 files changed, 295 insertions, 102 deletions

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index a78556514a87..ec54a57c4690 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -32,26 +32,26 @@ static struct ctl_table root_table[] = {
         },
         { }
 };
-static struct ctl_table_root sysctl_table_root;
-static struct ctl_dir sysctl_root_dir = {
-        .header = {
+static struct ctl_table_root sysctl_table_root = {
+        .default_set.list = LIST_HEAD_INIT(sysctl_table_root.default_set.dir.header.ctl_entry),
+        .default_set.dir.header = {
                 {{.count = 1,
                   .nreg = 1,
                   .ctl_table = root_table,
                   .ctl_entry = LIST_HEAD_INIT(sysctl_table_root.default_set.list),}},
+                .ctl_table_arg = root_table,
                 .root = &sysctl_table_root,
                 .set = &sysctl_table_root.default_set,
         },
 };
-static struct ctl_table_root sysctl_table_root = {
-        .root_list = LIST_HEAD_INIT(sysctl_table_root.root_list),
-        .default_set.list = LIST_HEAD_INIT(sysctl_root_dir.header.ctl_entry),
-        .default_set.root = &sysctl_table_root,
-};
 
 static DEFINE_SPINLOCK(sysctl_lock);
 
 static void drop_sysctl_table(struct ctl_table_header *header);
+static int sysctl_follow_link(struct ctl_table_header **phead,
+        struct ctl_table **pentry, struct nsproxy *namespaces);
+static int insert_links(struct ctl_table_header *head);
+static void put_links(struct ctl_table_header *header);
 
 static void sysctl_print_dir(struct ctl_dir *dir)
 {
@@ -76,9 +76,9 @@ static int namecmp(const char *name1, int len1, const char *name2, int len2)
 }
 
 static struct ctl_table *find_entry(struct ctl_table_header **phead,
-        struct ctl_table_set *set, struct ctl_dir *dir,
-        const char *name, int namelen)
+        struct ctl_dir *dir, const char *name, int namelen)
 {
+        struct ctl_table_set *set = dir->header.set;
         struct ctl_table_header *head;
         struct ctl_table *entry;
 
@@ -119,11 +119,21 @@ static void erase_header(struct ctl_table_header *head)
         list_del_init(&head->ctl_entry);
 }
 
-static void insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
+static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
 {
+        int err;
+
+        dir->header.nreg++;
         header->parent = dir;
-        header->parent->header.nreg++;
+        err = insert_links(header);
+        if (err)
+                goto fail_links;
         list_add_tail(&header->ctl_entry, &header->set->list);
+        return 0;
+fail_links:
+        header->parent = NULL;
+        drop_sysctl_table(&dir->header);
+        return err;
 }
 
 /* called under sysctl_lock */
@@ -212,72 +222,39 @@ lookup_header_set(struct ctl_table_root *root, struct nsproxy *namespaces)
         return set;
 }
 
-static struct list_head *
-lookup_header_list(struct ctl_table_root *root, struct nsproxy *namespaces)
-{
-        struct ctl_table_set *set = lookup_header_set(root, namespaces);
-        return &set->list;
-}
-
 static struct ctl_table *lookup_entry(struct ctl_table_header **phead,
                                       struct ctl_dir *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, 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);
+        entry = find_entry(&head, dir, name, namelen);
+        if (entry && use_table(head))
+                *phead = head;
+        else
+                entry = NULL;
         spin_unlock(&sysctl_lock);
         return entry;
 }
 
 static struct ctl_table_header *next_usable_entry(struct ctl_dir *dir,
-        struct ctl_table_root *root, struct list_head *tmp)
+                                                  struct list_head *tmp)
 {
-        struct nsproxy *namespaces = current->nsproxy;
-        struct list_head *header_list;
+        struct ctl_table_set *set = dir->header.set;
         struct ctl_table_header *head;
 
-        goto next;
-        for (;;) {
+        for (tmp = tmp->next; tmp != &set->list; tmp = tmp->next) {
                 head = list_entry(tmp, struct ctl_table_header, ctl_entry);
-                root = head->root;
 
                 if (head->parent != dir ||
                     !head->ctl_table->procname ||
                     !use_table(head))
-                        goto next;
-
-                return head;
-        next:
-                tmp = tmp->next;
-                header_list = lookup_header_list(root, namespaces);
-                if (tmp != header_list)
                         continue;
 
-                do {
-                        root = list_entry(root->root_list.next,
-                                        struct ctl_table_root, root_list);
-                        if (root == &sysctl_table_root)
-                                goto out;
-                        header_list = lookup_header_list(root, namespaces);
-                } while (list_empty(header_list));
-                tmp = header_list->next;
+                return head;
         }
-out:
         return NULL;
 }
 
@@ -288,8 +265,7 @@ static void first_entry(struct ctl_dir *dir,
         struct ctl_table *entry = NULL;
 
         spin_lock(&sysctl_lock);
-        head = next_usable_entry(dir, &sysctl_table_root,
-                                 &sysctl_table_root.default_set.list);
+        head = next_usable_entry(dir, &dir->header.set->list);
         spin_unlock(&sysctl_lock);
         if (head)
                 entry = head->ctl_table;
@@ -306,7 +282,7 @@ static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentr
         if (!entry->procname) {
                 spin_lock(&sysctl_lock);
                 unuse_table(head);
-                head = next_usable_entry(head->parent, head->root, &head->ctl_entry);
+                head = next_usable_entry(head->parent, &head->ctl_entry);
                 spin_unlock(&sysctl_lock);
                 if (head)
                         entry = head->ctl_table;
@@ -317,9 +293,6 @@ static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentr
 
 void register_sysctl_root(struct ctl_table_root *root)
 {
-        spin_lock(&sysctl_lock);
-        list_add_tail(&root->root_list, &sysctl_table_root.root_list);
-        spin_unlock(&sysctl_lock);
 }
 
 /*
@@ -386,7 +359,7 @@ static struct ctl_table_header *grab_header(struct inode *inode)
 {
         struct ctl_table_header *head = PROC_I(inode)->sysctl;
         if (!head)
-                head = &sysctl_root_dir.header;
+                head = &sysctl_table_root.default_set.dir.header;
         return sysctl_head_grab(head);
 }
 
@@ -400,6 +373,7 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
         struct inode *inode;
         struct dentry *err = ERR_PTR(-ENOENT);
         struct ctl_dir *ctl_dir;
+        int ret;
 
         if (IS_ERR(head))
                 return ERR_CAST(head);
@@ -410,6 +384,11 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
         if (!p)
                 goto out;
 
+        ret = sysctl_follow_link(&h, &p, current->nsproxy);
+        err = ERR_PTR(ret);
+        if (ret)
+                goto out;
+
         err = ERR_PTR(-ENOMEM);
         inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
         if (h)
@@ -547,6 +526,25 @@ static int proc_sys_fill_cache(struct file *filp, void *dirent,
         return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
 }
 
+static int proc_sys_link_fill_cache(struct file *filp, void *dirent,
+                                    filldir_t filldir,
+                                    struct ctl_table_header *head,
+                                    struct ctl_table *table)
+{
+        int err, ret = 0;
+        head = sysctl_head_grab(head);
+
+        /* It is not an error if we can not follow the link ignore it */
+        err = sysctl_follow_link(&head, &table, current->nsproxy);
+        if (err)
+                goto out;
+
+        ret = proc_sys_fill_cache(filp, dirent, filldir, head, table);
+out:
+        sysctl_head_finish(head);
+        return ret;
+}
+
 static int scan(struct ctl_table_header *head, ctl_table *table,
                 unsigned long *pos, struct file *file,
                 void *dirent, filldir_t filldir)
@@ -556,7 +554,10 @@ static int scan(struct ctl_table_header *head, ctl_table *table,
         if ((*pos)++ < file->f_pos)
                 return 0;
 
-        res = proc_sys_fill_cache(file, dirent, filldir, head, table);
+        if (unlikely(S_ISLNK(table->mode)))
+                res = proc_sys_link_fill_cache(file, dirent, filldir, head, table);
+        else
+                res = proc_sys_fill_cache(file, dirent, filldir, head, table);
 
         if (res == 0)
                 file->f_pos = *pos;
@@ -757,13 +758,13 @@ static const struct dentry_operations proc_sys_dentry_operations = {
         .d_compare      = proc_sys_compare,
 };
 
-static struct ctl_dir *find_subdir(struct ctl_table_set *set, struct ctl_dir *dir,
-        const char *name, int namelen)
+static struct ctl_dir *find_subdir(struct ctl_dir *dir,
+                                   const char *name, int namelen)
 {
         struct ctl_table_header *head;
         struct ctl_table *entry;
 
-        entry = find_entry(&head, set, dir, name, namelen);
+        entry = find_entry(&head, dir, name, namelen);
         if (!entry)
                 return ERR_PTR(-ENOENT);
         if (S_ISDIR(entry->mode))
@@ -772,7 +773,7 @@ static struct ctl_dir *find_subdir(struct ctl_table_set *set, struct ctl_dir *di
 }
 
 static struct ctl_dir *new_dir(struct ctl_table_set *set,
-        const char *name, int namelen)
+                               const char *name, int namelen)
 {
         struct ctl_table *table;
         struct ctl_dir *new;
@@ -789,22 +790,19 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set,
         new_name[namelen] = '\0';
         table[0].procname = new_name;
         table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
-        init_header(&new->header, set->root, set, table);
+        init_header(&new->header, set->dir.header.root, set, table);
 
         return new;
 }
 
-static struct ctl_dir *get_subdir(struct ctl_table_set *set,
-        struct ctl_dir *dir, const char *name, int namelen)
+static struct ctl_dir *get_subdir(struct ctl_dir *dir,
+                                  const char *name, int namelen)
 {
+        struct ctl_table_set *set = dir->header.set;
         struct ctl_dir *subdir, *new = NULL;
 
         spin_lock(&sysctl_lock);
-        subdir = find_subdir(dir->header.set, dir, name, namelen);
-        if (!IS_ERR(subdir))
-                goto found;
-        if ((PTR_ERR(subdir) == -ENOENT) && set != dir->header.set)
-                subdir = find_subdir(set, dir, name, namelen);
+        subdir = find_subdir(dir, name, namelen);
         if (!IS_ERR(subdir))
                 goto found;
         if (PTR_ERR(subdir) != -ENOENT)
@@ -817,13 +815,14 @@ static struct ctl_dir *get_subdir(struct ctl_table_set *set,
         if (!new)
                 goto failed;
 
-        subdir = find_subdir(set, dir, name, namelen);
+        subdir = find_subdir(dir, name, namelen);
         if (!IS_ERR(subdir))
                 goto found;
         if (PTR_ERR(subdir) != -ENOENT)
                 goto failed;
 
-        insert_header(dir, &new->header);
+        if (insert_header(dir, &new->header))
+                goto failed;
         subdir = new;
 found:
         subdir->header.nreg++;
@@ -841,6 +840,57 @@ failed:
         return subdir;
 }
 
+static struct ctl_dir *xlate_dir(struct ctl_table_set *set, struct ctl_dir *dir)
+{
+        struct ctl_dir *parent;
+        const char *procname;
+        if (!dir->header.parent)
+                return &set->dir;
+        parent = xlate_dir(set, dir->header.parent);
+        if (IS_ERR(parent))
+                return parent;
+        procname = dir->header.ctl_table[0].procname;
+        return find_subdir(parent, procname, strlen(procname));
+}
+
+static int sysctl_follow_link(struct ctl_table_header **phead,
+        struct ctl_table **pentry, struct nsproxy *namespaces)
+{
+        struct ctl_table_header *head;
+        struct ctl_table_root *root;
+        struct ctl_table_set *set;
+        struct ctl_table *entry;
+        struct ctl_dir *dir;
+        int ret;
+
+        /* Get out quickly if not a link */
+        if (!S_ISLNK((*pentry)->mode))
+                return 0;
+
+        ret = 0;
+        spin_lock(&sysctl_lock);
+        root = (*pentry)->data;
+        set = lookup_header_set(root, namespaces);
+        dir = xlate_dir(set, (*phead)->parent);
+        if (IS_ERR(dir))
+                ret = PTR_ERR(dir);
+        else {
+                const char *procname = (*pentry)->procname;
+                head = NULL;
+                entry = find_entry(&head, dir, procname, strlen(procname));
+                ret = -ENOENT;
+                if (entry && use_table(head)) {
+                        unuse_table(*phead);
+                        *phead = head;
+                        *pentry = entry;
+                        ret = 0;
+                }
+        }
+
+        spin_unlock(&sysctl_lock);
+        return ret;
+}
+
 static int sysctl_check_table_dups(const char *path, struct ctl_table *old,
         struct ctl_table *table)
 {
@@ -859,30 +909,21 @@ static int sysctl_check_table_dups(const char *path, struct ctl_table *old,
         return error;
 }
 
-static int sysctl_check_dups(struct nsproxy *namespaces,
-        struct ctl_dir *dir,
+static int sysctl_check_dups(struct ctl_dir *dir,
         const char *path, struct ctl_table *table)
 {
-        struct ctl_table_root *root;
         struct ctl_table_set *set;
         struct ctl_table_header *head;
         int error = 0;
 
-        root = &sysctl_table_root;
-        do {
-                set = lookup_header_set(root, namespaces);
-
-                list_for_each_entry(head, &set->list, ctl_entry) {
-                        if (head->unregistering)
-                                continue;
-                        if (head->parent != dir)
-                                continue;
-                        error = sysctl_check_table_dups(path, head->ctl_table,
-                                                        table);
-                }
-                root = list_entry(root->root_list.next,
-                                  struct ctl_table_root, root_list);
-        } while (root != &sysctl_table_root);
+        set = dir->header.set;
+        list_for_each_entry(head, &set->list, ctl_entry) {
+                if (head->unregistering)
+                        continue;
+                if (head->parent != dir)
+                        continue;
+                error = sysctl_check_table_dups(path, head->ctl_table, table);
+        }
         return error;
 }
 
@@ -932,6 +973,115 @@ static int sysctl_check_table(const char *path, struct ctl_table *table)
         return err;
 }
 
+static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table *table,
+        struct ctl_table_root *link_root)
+{
+        struct ctl_table *link_table, *entry, *link;
+        struct ctl_table_header *links;
+        char *link_name;
+        int nr_entries, name_bytes;
+
+        name_bytes = 0;
+        nr_entries = 0;
+        for (entry = table; entry->procname; entry++) {
+                nr_entries++;
+                name_bytes += strlen(entry->procname) + 1;
+        }
+
+        links = kzalloc(sizeof(struct ctl_table_header) +
+                        sizeof(struct ctl_table)*(nr_entries + 1) +
+                        name_bytes,
+                        GFP_KERNEL);
+
+        if (!links)
+                return NULL;
+
+        link_table = (struct ctl_table *)(links + 1);
+        link_name = (char *)&link_table[nr_entries + 1];
+
+        for (link = link_table, entry = table; entry->procname; link++, entry++) {
+                int len = strlen(entry->procname) + 1;
+                memcpy(link_name, entry->procname, len);
+                link->procname = link_name;
+                link->mode = S_IFLNK|S_IRWXUGO;
+                link->data = link_root;
+                link_name += len;
+        }
+        init_header(links, dir->header.root, dir->header.set, link_table);
+        links->nreg = nr_entries;
+
+        return links;
+}
+
+static bool get_links(struct ctl_dir *dir,
+        struct ctl_table *table, struct ctl_table_root *link_root)
+{
+        struct ctl_table_header *head;
+        struct ctl_table *entry, *link;
+
+        /* Are there links available for every entry in table? */
+        for (entry = table; entry->procname; entry++) {
+                const char *procname = entry->procname;
+                link = find_entry(&head, dir, procname, strlen(procname));
+                if (!link)
+                        return false;
+                if (S_ISDIR(link->mode) && S_ISDIR(entry->mode))
+                        continue;
+                if (S_ISLNK(link->mode) && (link->data == link_root))
+                        continue;
+                return false;
+        }
+
+        /* The checks passed.  Increase the registration count on the links */
+        for (entry = table; entry->procname; entry++) {
+                const char *procname = entry->procname;
+                link = find_entry(&head, dir, procname, strlen(procname));
+                head->nreg++;
+        }
+        return true;
+}
+
+static int insert_links(struct ctl_table_header *head)
+{
+        struct ctl_table_set *root_set = &sysctl_table_root.default_set;
+        struct ctl_dir *core_parent = NULL;
+        struct ctl_table_header *links;
+        int err;
+
+        if (head->set == root_set)
+                return 0;
+
+        core_parent = xlate_dir(root_set, head->parent);
+        if (IS_ERR(core_parent))
+                return 0;
+
+        if (get_links(core_parent, head->ctl_table, head->root))
+                return 0;
+
+        core_parent->header.nreg++;
+        spin_unlock(&sysctl_lock);
+
+        links = new_links(core_parent, head->ctl_table, head->root);
+
+        spin_lock(&sysctl_lock);
+        err = -ENOMEM;
+        if (!links)
+                goto out;
+
+        err = 0;
+        if (get_links(core_parent, head->ctl_table, head->root)) {
+                kfree(links);
+                goto out;
+        }
+
+        err = insert_header(core_parent, links);
+        if (err)
+                kfree(links);
+out:
+        drop_sysctl_table(&core_parent->header);
+        return err;
+}
+
 /**
  * __register_sysctl_table - register a leaf sysctl table
  * @root: List of sysctl headers to register on
@@ -980,6 +1130,7 @@ struct ctl_table_header *__register_sysctl_table(
         struct nsproxy *namespaces,
         const char *path, struct ctl_table *table)
 {
+        struct ctl_table_header *links = NULL;
         struct ctl_table_header *header;
         const char *name, *nextname;
         struct ctl_table_set *set;
@@ -995,7 +1146,7 @@ struct ctl_table_header *__register_sysctl_table(
 
         spin_lock(&sysctl_lock);
         header->set = set = lookup_header_set(root, namespaces);
-        dir = &sysctl_root_dir;
+        dir = &set->dir;
         dir->header.nreg++;
         spin_unlock(&sysctl_lock);
 
@@ -1012,22 +1163,28 @@ struct ctl_table_header *__register_sysctl_table(
                 if (namelen == 0)
                         continue;
 
-                dir = get_subdir(set, dir, name, namelen);
+                dir = get_subdir(dir, name, namelen);
                 if (IS_ERR(dir))
                         goto fail;
         }
+
         spin_lock(&sysctl_lock);
-        if (sysctl_check_dups(namespaces, dir, path, table))
+        if (sysctl_check_dups(dir, path, table))
+                goto fail_put_dir_locked;
+
+        if (insert_header(dir, header))
                 goto fail_put_dir_locked;
-        insert_header(dir, header);
+
         drop_sysctl_table(&dir->header);
         spin_unlock(&sysctl_lock);
 
         return header;
+
 fail_put_dir_locked:
         drop_sysctl_table(&dir->header);
         spin_unlock(&sysctl_lock);
 fail:
+        kfree(links);
         kfree(header);
         dump_stack();
         return NULL;
@@ -1249,6 +1406,40 @@ struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
 }
 EXPORT_SYMBOL(register_sysctl_table);
 
+static void put_links(struct ctl_table_header *header)
+{
+        struct ctl_table_set *root_set = &sysctl_table_root.default_set;
+        struct ctl_table_root *root = header->root;
+        struct ctl_dir *parent = header->parent;
+        struct ctl_dir *core_parent;
+        struct ctl_table *entry;
+
+        if (header->set == root_set)
+                return;
+
+        core_parent = xlate_dir(root_set, parent);
+        if (IS_ERR(core_parent))
+                return;
+
+        for (entry = header->ctl_table; entry->procname; entry++) {
+                struct ctl_table_header *link_head;
+                struct ctl_table *link;
+                const char *name = entry->procname;
+
+                link = find_entry(&link_head, core_parent, name, strlen(name));
+                if (link &&
+                    ((S_ISDIR(link->mode) && S_ISDIR(entry->mode)) ||
+                     (S_ISLNK(link->mode) && (link->data == root)))) {
+                        drop_sysctl_table(link_head);
+                }
+                else {
+                        printk(KERN_ERR "sysctl link missing during unregister: ");
+                        sysctl_print_dir(parent);
+                        printk(KERN_CONT "/%s\n", name);
+                }
+        }
+}
+
 static void drop_sysctl_table(struct ctl_table_header *header)
 {
         struct ctl_dir *parent = header->parent;
@@ -1256,6 +1447,7 @@ static void drop_sysctl_table(struct ctl_table_header *header)
         if (--header->nreg)
                 return;
 
+        put_links(header);
         start_unregistering(header);
         if (!--header->count)
                 kfree_rcu(header, rcu);
@@ -1301,13 +1493,14 @@ void unregister_sysctl_table(struct ctl_table_header * header)
 }
 EXPORT_SYMBOL(unregister_sysctl_table);
 
-void setup_sysctl_set(struct ctl_table_set *p,
+void setup_sysctl_set(struct ctl_table_set *set,
         struct ctl_table_root *root,
         int (*is_seen)(struct ctl_table_set *))
 {
-        INIT_LIST_HEAD(&p->list);
-        p->root = root;
-        p->is_seen = is_seen;
+        memset(set, sizeof(*set), 0);
+        INIT_LIST_HEAD(&set->list);
+        set->is_seen = is_seen;
+        init_header(&set->dir.header, root, set, root_table);
 }
 
 void retire_sysctl_set(struct ctl_table_set *set)