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![Al Viro](/assets/img/avatar_default.png)
nothing blocking there, since all instances of sysctl ->permissions() method are non-blocking - both of them, that is. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
436 lines
10 KiB
C
436 lines
10 KiB
C
/*
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* /proc/sys support
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*/
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#include <linux/init.h>
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#include <linux/sysctl.h>
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#include <linux/proc_fs.h>
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#include <linux/security.h>
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#include <linux/namei.h>
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#include "internal.h"
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static const struct dentry_operations proc_sys_dentry_operations;
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static const struct file_operations proc_sys_file_operations;
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static const struct inode_operations proc_sys_inode_operations;
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static const struct file_operations proc_sys_dir_file_operations;
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static const struct inode_operations proc_sys_dir_operations;
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static struct inode *proc_sys_make_inode(struct super_block *sb,
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struct ctl_table_header *head, struct ctl_table *table)
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{
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struct inode *inode;
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struct proc_inode *ei;
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inode = new_inode(sb);
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if (!inode)
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goto out;
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inode->i_ino = get_next_ino();
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sysctl_head_get(head);
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ei = PROC_I(inode);
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ei->sysctl = head;
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ei->sysctl_entry = table;
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inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
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inode->i_mode = table->mode;
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if (!table->child) {
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inode->i_mode |= S_IFREG;
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inode->i_op = &proc_sys_inode_operations;
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inode->i_fop = &proc_sys_file_operations;
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} else {
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inode->i_mode |= S_IFDIR;
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inode->i_nlink = 0;
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inode->i_op = &proc_sys_dir_operations;
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inode->i_fop = &proc_sys_dir_file_operations;
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}
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out:
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return inode;
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}
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static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)
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{
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int len;
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for ( ; p->procname; p++) {
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if (!p->procname)
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continue;
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len = strlen(p->procname);
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if (len != name->len)
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continue;
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if (memcmp(p->procname, name->name, len) != 0)
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continue;
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/* I have a match */
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return p;
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}
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return NULL;
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}
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static struct ctl_table_header *grab_header(struct inode *inode)
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{
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if (PROC_I(inode)->sysctl)
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return sysctl_head_grab(PROC_I(inode)->sysctl);
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else
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return sysctl_head_next(NULL);
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}
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static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
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struct nameidata *nd)
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{
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struct ctl_table_header *head = grab_header(dir);
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struct ctl_table *table = PROC_I(dir)->sysctl_entry;
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struct ctl_table_header *h = NULL;
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struct qstr *name = &dentry->d_name;
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struct ctl_table *p;
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struct inode *inode;
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struct dentry *err = ERR_PTR(-ENOENT);
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if (IS_ERR(head))
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return ERR_CAST(head);
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if (table && !table->child) {
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WARN_ON(1);
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goto out;
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}
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table = table ? table->child : head->ctl_table;
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p = find_in_table(table, name);
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if (!p) {
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for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
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if (h->attached_to != table)
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continue;
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p = find_in_table(h->attached_by, name);
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if (p)
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break;
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}
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}
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if (!p)
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goto out;
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err = ERR_PTR(-ENOMEM);
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inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
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if (h)
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sysctl_head_finish(h);
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if (!inode)
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goto out;
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err = NULL;
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d_set_d_op(dentry, &proc_sys_dentry_operations);
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d_add(dentry, inode);
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out:
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sysctl_head_finish(head);
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return err;
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}
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static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
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size_t count, loff_t *ppos, int write)
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{
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struct inode *inode = filp->f_path.dentry->d_inode;
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struct ctl_table_header *head = grab_header(inode);
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struct ctl_table *table = PROC_I(inode)->sysctl_entry;
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ssize_t error;
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size_t res;
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if (IS_ERR(head))
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return PTR_ERR(head);
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/*
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* At this point we know that the sysctl was not unregistered
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* and won't be until we finish.
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*/
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error = -EPERM;
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if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))
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goto out;
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/* if that can happen at all, it should be -EINVAL, not -EISDIR */
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error = -EINVAL;
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if (!table->proc_handler)
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goto out;
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/* careful: calling conventions are nasty here */
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res = count;
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error = table->proc_handler(table, write, buf, &res, ppos);
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if (!error)
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error = res;
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out:
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sysctl_head_finish(head);
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return error;
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}
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static ssize_t proc_sys_read(struct file *filp, char __user *buf,
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size_t count, loff_t *ppos)
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{
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return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
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}
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static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
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}
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static int proc_sys_fill_cache(struct file *filp, void *dirent,
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filldir_t filldir,
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struct ctl_table_header *head,
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struct ctl_table *table)
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{
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struct dentry *child, *dir = filp->f_path.dentry;
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struct inode *inode;
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struct qstr qname;
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ino_t ino = 0;
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unsigned type = DT_UNKNOWN;
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qname.name = table->procname;
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qname.len = strlen(table->procname);
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qname.hash = full_name_hash(qname.name, qname.len);
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child = d_lookup(dir, &qname);
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if (!child) {
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child = d_alloc(dir, &qname);
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if (child) {
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inode = proc_sys_make_inode(dir->d_sb, head, table);
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if (!inode) {
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dput(child);
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return -ENOMEM;
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} else {
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d_set_d_op(child, &proc_sys_dentry_operations);
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d_add(child, inode);
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}
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} else {
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return -ENOMEM;
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}
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}
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inode = child->d_inode;
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ino = inode->i_ino;
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type = inode->i_mode >> 12;
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dput(child);
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return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
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}
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static int scan(struct ctl_table_header *head, ctl_table *table,
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unsigned long *pos, struct file *file,
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void *dirent, filldir_t filldir)
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{
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for (; table->procname; table++, (*pos)++) {
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int res;
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/* Can't do anything without a proc name */
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if (!table->procname)
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continue;
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if (*pos < file->f_pos)
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continue;
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res = proc_sys_fill_cache(file, dirent, filldir, head, table);
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if (res)
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return res;
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file->f_pos = *pos + 1;
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}
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return 0;
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}
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static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
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{
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struct dentry *dentry = filp->f_path.dentry;
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struct inode *inode = dentry->d_inode;
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struct ctl_table_header *head = grab_header(inode);
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struct ctl_table *table = PROC_I(inode)->sysctl_entry;
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struct ctl_table_header *h = NULL;
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unsigned long pos;
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int ret = -EINVAL;
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if (IS_ERR(head))
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return PTR_ERR(head);
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if (table && !table->child) {
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WARN_ON(1);
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goto out;
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}
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table = table ? table->child : head->ctl_table;
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ret = 0;
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/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
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if (filp->f_pos == 0) {
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if (filldir(dirent, ".", 1, filp->f_pos,
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inode->i_ino, DT_DIR) < 0)
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goto out;
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filp->f_pos++;
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}
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if (filp->f_pos == 1) {
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if (filldir(dirent, "..", 2, filp->f_pos,
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parent_ino(dentry), DT_DIR) < 0)
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goto out;
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filp->f_pos++;
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}
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pos = 2;
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ret = scan(head, table, &pos, filp, dirent, filldir);
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if (ret)
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goto out;
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for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
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if (h->attached_to != table)
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continue;
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ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);
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if (ret) {
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sysctl_head_finish(h);
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break;
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}
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}
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ret = 1;
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out:
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sysctl_head_finish(head);
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return ret;
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}
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static int proc_sys_permission(struct inode *inode, int mask,unsigned int flags)
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{
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/*
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* sysctl entries that are not writeable,
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* are _NOT_ writeable, capabilities or not.
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*/
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struct ctl_table_header *head;
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struct ctl_table *table;
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int error;
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/* Executable files are not allowed under /proc/sys/ */
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if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
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return -EACCES;
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head = grab_header(inode);
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if (IS_ERR(head))
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return PTR_ERR(head);
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table = PROC_I(inode)->sysctl_entry;
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if (!table) /* global root - r-xr-xr-x */
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error = mask & MAY_WRITE ? -EACCES : 0;
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else /* Use the permissions on the sysctl table entry */
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error = sysctl_perm(head->root, table, mask);
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sysctl_head_finish(head);
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return error;
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}
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static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
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return -EPERM;
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error = inode_change_ok(inode, attr);
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if (error)
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return error;
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if ((attr->ia_valid & ATTR_SIZE) &&
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attr->ia_size != i_size_read(inode)) {
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error = vmtruncate(inode, attr->ia_size);
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if (error)
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return error;
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}
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setattr_copy(inode, attr);
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mark_inode_dirty(inode);
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return 0;
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}
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static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
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{
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struct inode *inode = dentry->d_inode;
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struct ctl_table_header *head = grab_header(inode);
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struct ctl_table *table = PROC_I(inode)->sysctl_entry;
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if (IS_ERR(head))
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return PTR_ERR(head);
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generic_fillattr(inode, stat);
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if (table)
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stat->mode = (stat->mode & S_IFMT) | table->mode;
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sysctl_head_finish(head);
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return 0;
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}
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static const struct file_operations proc_sys_file_operations = {
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.read = proc_sys_read,
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.write = proc_sys_write,
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.llseek = default_llseek,
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};
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static const struct file_operations proc_sys_dir_file_operations = {
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.readdir = proc_sys_readdir,
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.llseek = generic_file_llseek,
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};
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static const struct inode_operations proc_sys_inode_operations = {
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.permission = proc_sys_permission,
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.setattr = proc_sys_setattr,
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.getattr = proc_sys_getattr,
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};
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static const struct inode_operations proc_sys_dir_operations = {
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.lookup = proc_sys_lookup,
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.permission = proc_sys_permission,
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.setattr = proc_sys_setattr,
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.getattr = proc_sys_getattr,
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};
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static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
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{
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if (nd->flags & LOOKUP_RCU)
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return -ECHILD;
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return !PROC_I(dentry->d_inode)->sysctl->unregistering;
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}
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static int proc_sys_delete(const struct dentry *dentry)
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{
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return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
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}
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static int proc_sys_compare(const struct dentry *parent,
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const struct inode *pinode,
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const struct dentry *dentry, const struct inode *inode,
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unsigned int len, const char *str, const struct qstr *name)
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{
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struct ctl_table_header *head;
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/* Although proc doesn't have negative dentries, rcu-walk means
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* that inode here can be NULL */
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/* AV: can it, indeed? */
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if (!inode)
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return 1;
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if (name->len != len)
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return 1;
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if (memcmp(name->name, str, len))
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return 1;
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head = rcu_dereference(PROC_I(inode)->sysctl);
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return !head || !sysctl_is_seen(head);
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}
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static const struct dentry_operations proc_sys_dentry_operations = {
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.d_revalidate = proc_sys_revalidate,
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.d_delete = proc_sys_delete,
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.d_compare = proc_sys_compare,
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};
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int __init proc_sys_init(void)
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{
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struct proc_dir_entry *proc_sys_root;
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proc_sys_root = proc_mkdir("sys", NULL);
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proc_sys_root->proc_iops = &proc_sys_dir_operations;
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proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
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proc_sys_root->nlink = 0;
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return 0;
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}
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