kernel-ark/fs/proc/proc_sysctl.c
Pavel Emelyanov d7321cd624 sysctl: add the ->permissions callback on the ctl_table_root
When reading from/writing to some table, a root, which this table came from,
may affect this table's permissions, depending on who is working with the
table.

The core hunk is at the bottom of this patch.  All the rest is just pushing
the ctl_table_root argument up to the sysctl_perm() function.

This will be mostly (only?) used in the net sysctls.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Denis V. Lunev <den@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-29 08:06:23 -07:00

451 lines
10 KiB
C

/*
* /proc/sys support
*/
#include <linux/sysctl.h>
#include <linux/proc_fs.h>
#include <linux/security.h>
#include "internal.h"
static struct dentry_operations proc_sys_dentry_operations;
static const struct file_operations proc_sys_file_operations;
static const struct inode_operations proc_sys_inode_operations;
static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table)
{
/* Refresh the cached information bits in the inode */
if (table) {
inode->i_uid = 0;
inode->i_gid = 0;
inode->i_mode = table->mode;
if (table->proc_handler) {
inode->i_mode |= S_IFREG;
inode->i_nlink = 1;
} else {
inode->i_mode |= S_IFDIR;
inode->i_nlink = 0; /* It is too hard to figure out */
}
}
}
static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *table)
{
struct inode *inode;
struct proc_inode *dir_ei, *ei;
int depth;
inode = new_inode(dir->i_sb);
if (!inode)
goto out;
/* A directory is always one deeper than it's parent */
dir_ei = PROC_I(dir);
depth = dir_ei->fd + 1;
ei = PROC_I(inode);
ei->fd = depth;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_op = &proc_sys_inode_operations;
inode->i_fop = &proc_sys_file_operations;
inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
proc_sys_refresh_inode(inode, table);
out:
return inode;
}
static struct dentry *proc_sys_ancestor(struct dentry *dentry, int depth)
{
for (;;) {
struct proc_inode *ei;
ei = PROC_I(dentry->d_inode);
if (ei->fd == depth)
break; /* found */
dentry = dentry->d_parent;
}
return dentry;
}
static struct ctl_table *proc_sys_lookup_table_one(struct ctl_table *table,
struct qstr *name)
{
int len;
for ( ; table->ctl_name || table->procname; table++) {
if (!table->procname)
continue;
len = strlen(table->procname);
if (len != name->len)
continue;
if (memcmp(table->procname, name->name, len) != 0)
continue;
/* I have a match */
return table;
}
return NULL;
}
static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry,
struct ctl_table *table)
{
struct dentry *ancestor;
struct proc_inode *ei;
int depth, i;
ei = PROC_I(dentry->d_inode);
depth = ei->fd;
if (depth == 0)
return table;
for (i = 1; table && (i <= depth); i++) {
ancestor = proc_sys_ancestor(dentry, i);
table = proc_sys_lookup_table_one(table, &ancestor->d_name);
if (table)
table = table->child;
}
return table;
}
static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent,
struct qstr *name,
struct ctl_table *table)
{
table = proc_sys_lookup_table(dparent, table);
if (table)
table = proc_sys_lookup_table_one(table, name);
return table;
}
static struct ctl_table *do_proc_sys_lookup(struct dentry *parent,
struct qstr *name,
struct ctl_table_header **ptr)
{
struct ctl_table_header *head;
struct ctl_table *table = NULL;
for (head = sysctl_head_next(NULL); head;
head = sysctl_head_next(head)) {
table = proc_sys_lookup_entry(parent, name, head->ctl_table);
if (table)
break;
}
*ptr = head;
return table;
}
static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
struct ctl_table_header *head;
struct inode *inode;
struct dentry *err;
struct ctl_table *table;
err = ERR_PTR(-ENOENT);
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
if (!table)
goto out;
err = ERR_PTR(-ENOMEM);
inode = proc_sys_make_inode(dir, table);
if (!inode)
goto out;
err = NULL;
dentry->d_op = &proc_sys_dentry_operations;
d_add(dentry, inode);
out:
sysctl_head_finish(head);
return err;
}
static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
size_t count, loff_t *ppos, int write)
{
struct dentry *dentry = filp->f_dentry;
struct ctl_table_header *head;
struct ctl_table *table;
ssize_t error;
size_t res;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* Has the sysctl entry disappeared on us? */
error = -ENOENT;
if (!table)
goto out;
/* Has the sysctl entry been replaced by a directory? */
error = -EISDIR;
if (!table->proc_handler)
goto out;
/*
* At this point we know that the sysctl was not unregistered
* and won't be until we finish.
*/
error = -EPERM;
if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))
goto out;
/* careful: calling conventions are nasty here */
res = count;
error = table->proc_handler(table, write, filp, buf, &res, ppos);
if (!error)
error = res;
out:
sysctl_head_finish(head);
return error;
}
static ssize_t proc_sys_read(struct file *filp, char __user *buf,
size_t count, loff_t *ppos)
{
return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
}
static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
size_t count, loff_t *ppos)
{
return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
}
static int proc_sys_fill_cache(struct file *filp, void *dirent,
filldir_t filldir, struct ctl_table *table)
{
struct ctl_table_header *head;
struct ctl_table *child_table = NULL;
struct dentry *child, *dir = filp->f_path.dentry;
struct inode *inode;
struct qstr qname;
ino_t ino = 0;
unsigned type = DT_UNKNOWN;
int ret;
qname.name = table->procname;
qname.len = strlen(table->procname);
qname.hash = full_name_hash(qname.name, qname.len);
/* Suppress duplicates.
* Only fill a directory entry if it is the value that
* an ordinary lookup of that name returns. Hide all
* others.
*
* If we ever cache this translation in the dcache
* I should do a dcache lookup first. But for now
* it is just simpler not to.
*/
ret = 0;
child_table = do_proc_sys_lookup(dir, &qname, &head);
sysctl_head_finish(head);
if (child_table != table)
return 0;
child = d_lookup(dir, &qname);
if (!child) {
struct dentry *new;
new = d_alloc(dir, &qname);
if (new) {
inode = proc_sys_make_inode(dir->d_inode, table);
if (!inode)
child = ERR_PTR(-ENOMEM);
else {
new->d_op = &proc_sys_dentry_operations;
d_add(new, inode);
}
if (child)
dput(new);
else
child = new;
}
}
if (!child || IS_ERR(child) || !child->d_inode)
goto end_instantiate;
inode = child->d_inode;
if (inode) {
ino = inode->i_ino;
type = inode->i_mode >> 12;
}
dput(child);
end_instantiate:
if (!ino)
ino= find_inode_number(dir, &qname);
if (!ino)
ino = 1;
return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
}
static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_dentry;
struct inode *inode = dentry->d_inode;
struct ctl_table_header *head = NULL;
struct ctl_table *table;
unsigned long pos;
int ret;
ret = -ENOTDIR;
if (!S_ISDIR(inode->i_mode))
goto out;
ret = 0;
/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
if (filp->f_pos == 0) {
if (filldir(dirent, ".", 1, filp->f_pos,
inode->i_ino, DT_DIR) < 0)
goto out;
filp->f_pos++;
}
if (filp->f_pos == 1) {
if (filldir(dirent, "..", 2, filp->f_pos,
parent_ino(dentry), DT_DIR) < 0)
goto out;
filp->f_pos++;
}
pos = 2;
/* - Find each instance of the directory
* - Read all entries in each instance
* - Before returning an entry to user space lookup the entry
* by name and if I find a different entry don't return
* this one because it means it is a buried dup.
* For sysctl this should only happen for directory entries.
*/
for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {
table = proc_sys_lookup_table(dentry, head->ctl_table);
if (!table)
continue;
for (; table->ctl_name || table->procname; table++, pos++) {
/* Can't do anything without a proc name */
if (!table->procname)
continue;
if (pos < filp->f_pos)
continue;
if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)
goto out;
filp->f_pos = pos + 1;
}
}
ret = 1;
out:
sysctl_head_finish(head);
return ret;
}
static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *nd)
{
/*
* sysctl entries that are not writeable,
* are _NOT_ writeable, capabilities or not.
*/
struct ctl_table_header *head;
struct ctl_table *table;
struct dentry *dentry;
int mode;
int depth;
int error;
head = NULL;
depth = PROC_I(inode)->fd;
/* First check the cached permissions, in case we don't have
* enough information to lookup the sysctl table entry.
*/
error = -EACCES;
mode = inode->i_mode;
if (current->euid == 0)
mode >>= 6;
else if (in_group_p(0))
mode >>= 3;
if ((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask)
error = 0;
/* If we can't get a sysctl table entry the permission
* checks on the cached mode will have to be enough.
*/
if (!nd || !depth)
goto out;
dentry = nd->path.dentry;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
/* If the entry does not exist deny permission */
error = -EACCES;
if (!table)
goto out;
/* Use the permissions on the sysctl table entry */
error = sysctl_perm(head->root, table, mask);
out:
sysctl_head_finish(head);
return error;
}
static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = dentry->d_inode;
int error;
if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
return -EPERM;
error = inode_change_ok(inode, attr);
if (!error)
error = inode_setattr(inode, attr);
return error;
}
/* I'm lazy and don't distinguish between files and directories,
* until access time.
*/
static const struct file_operations proc_sys_file_operations = {
.read = proc_sys_read,
.write = proc_sys_write,
.readdir = proc_sys_readdir,
};
static const struct inode_operations proc_sys_inode_operations = {
.lookup = proc_sys_lookup,
.permission = proc_sys_permission,
.setattr = proc_sys_setattr,
};
static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
{
struct ctl_table_header *head;
struct ctl_table *table;
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
proc_sys_refresh_inode(dentry->d_inode, table);
sysctl_head_finish(head);
return !!table;
}
static struct dentry_operations proc_sys_dentry_operations = {
.d_revalidate = proc_sys_revalidate,
};
static struct proc_dir_entry *proc_sys_root;
int proc_sys_init(void)
{
proc_sys_root = proc_mkdir("sys", NULL);
proc_sys_root->proc_iops = &proc_sys_inode_operations;
proc_sys_root->proc_fops = &proc_sys_file_operations;
proc_sys_root->nlink = 0;
return 0;
}