linux-stable/fs/proc/proc_sysctl.c
Matteo Croce eec4844fae proc/sysctl: add shared variables for range check
In the sysctl code the proc_dointvec_minmax() function is often used to
validate the user supplied value between an allowed range.  This
function uses the extra1 and extra2 members from struct ctl_table as
minimum and maximum allowed value.

On sysctl handler declaration, in every source file there are some
readonly variables containing just an integer which address is assigned
to the extra1 and extra2 members, so the sysctl range is enforced.

The special values 0, 1 and INT_MAX are very often used as range
boundary, leading duplication of variables like zero=0, one=1,
int_max=INT_MAX in different source files:

    $ git grep -E '\.extra[12].*&(zero|one|int_max)' |wc -l
    248

Add a const int array containing the most commonly used values, some
macros to refer more easily to the correct array member, and use them
instead of creating a local one for every object file.

This is the bloat-o-meter output comparing the old and new binary
compiled with the default Fedora config:

    # scripts/bloat-o-meter -d vmlinux.o.old vmlinux.o
    add/remove: 2/2 grow/shrink: 0/2 up/down: 24/-188 (-164)
    Data                                         old     new   delta
    sysctl_vals                                    -      12     +12
    __kstrtab_sysctl_vals                          -      12     +12
    max                                           14      10      -4
    int_max                                       16       -     -16
    one                                           68       -     -68
    zero                                         128      28    -100
    Total: Before=20583249, After=20583085, chg -0.00%

[mcroce@redhat.com: tipc: remove two unused variables]
  Link: http://lkml.kernel.org/r/20190530091952.4108-1-mcroce@redhat.com
[akpm@linux-foundation.org: fix net/ipv6/sysctl_net_ipv6.c]
[arnd@arndb.de: proc/sysctl: make firmware loader table conditional]
  Link: http://lkml.kernel.org/r/20190617130014.1713870-1-arnd@arndb.de
[akpm@linux-foundation.org: fix fs/eventpoll.c]
Link: http://lkml.kernel.org/r/20190430180111.10688-1-mcroce@redhat.com
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-18 17:08:07 -07:00

1727 lines
42 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* /proc/sys support
*/
#include <linux/init.h>
#include <linux/sysctl.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/printk.h>
#include <linux/security.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/namei.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bpf-cgroup.h>
#include "internal.h"
static const 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 const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_operations;
/* shared constants to be used in various sysctls */
const int sysctl_vals[] = { 0, 1, INT_MAX };
EXPORT_SYMBOL(sysctl_vals);
/* Support for permanently empty directories */
struct ctl_table sysctl_mount_point[] = {
{ }
};
static bool is_empty_dir(struct ctl_table_header *head)
{
return head->ctl_table[0].child == sysctl_mount_point;
}
static void set_empty_dir(struct ctl_dir *dir)
{
dir->header.ctl_table[0].child = sysctl_mount_point;
}
static void clear_empty_dir(struct ctl_dir *dir)
{
dir->header.ctl_table[0].child = NULL;
}
void proc_sys_poll_notify(struct ctl_table_poll *poll)
{
if (!poll)
return;
atomic_inc(&poll->event);
wake_up_interruptible(&poll->wait);
}
static struct ctl_table root_table[] = {
{
.procname = "",
.mode = S_IFDIR|S_IRUGO|S_IXUGO,
},
{ }
};
static struct ctl_table_root sysctl_table_root = {
.default_set.dir.header = {
{{.count = 1,
.nreg = 1,
.ctl_table = root_table }},
.ctl_table_arg = root_table,
.root = &sysctl_table_root,
.set = &sysctl_table_root.default_set,
},
};
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);
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)
{
if (dir->header.parent)
sysctl_print_dir(dir->header.parent);
pr_cont("%s/", dir->header.ctl_table[0].procname);
}
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;
}
/* Called under sysctl_lock */
static struct ctl_table *find_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 rb_node *node = dir->root.rb_node;
while (node)
{
struct ctl_node *ctl_node;
const char *procname;
int cmp;
ctl_node = rb_entry(node, struct ctl_node, node);
head = ctl_node->header;
entry = &head->ctl_table[ctl_node - head->node];
procname = entry->procname;
cmp = namecmp(name, namelen, procname, strlen(procname));
if (cmp < 0)
node = node->rb_left;
else if (cmp > 0)
node = node->rb_right;
else {
*phead = head;
return entry;
}
}
return NULL;
}
static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
{
struct rb_node *node = &head->node[entry - head->ctl_table].node;
struct rb_node **p = &head->parent->root.rb_node;
struct rb_node *parent = NULL;
const char *name = entry->procname;
int namelen = strlen(name);
while (*p) {
struct ctl_table_header *parent_head;
struct ctl_table *parent_entry;
struct ctl_node *parent_node;
const char *parent_name;
int cmp;
parent = *p;
parent_node = rb_entry(parent, struct ctl_node, node);
parent_head = parent_node->header;
parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
parent_name = parent_entry->procname;
cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
if (cmp < 0)
p = &(*p)->rb_left;
else if (cmp > 0)
p = &(*p)->rb_right;
else {
pr_err("sysctl duplicate entry: ");
sysctl_print_dir(head->parent);
pr_cont("/%s\n", entry->procname);
return -EEXIST;
}
}
rb_link_node(node, parent, p);
rb_insert_color(node, &head->parent->root);
return 0;
}
static void erase_entry(struct ctl_table_header *head, struct ctl_table *entry)
{
struct rb_node *node = &head->node[entry - head->ctl_table].node;
rb_erase(node, &head->parent->root);
}
static void init_header(struct ctl_table_header *head,
struct ctl_table_root *root, struct ctl_table_set *set,
struct ctl_node *node, struct ctl_table *table)
{
head->ctl_table = table;
head->ctl_table_arg = table;
head->used = 0;
head->count = 1;
head->nreg = 1;
head->unregistering = NULL;
head->root = root;
head->set = set;
head->parent = NULL;
head->node = node;
INIT_HLIST_HEAD(&head->inodes);
if (node) {
struct ctl_table *entry;
for (entry = table; entry->procname; entry++, node++)
node->header = head;
}
}
static void erase_header(struct ctl_table_header *head)
{
struct ctl_table *entry;
for (entry = head->ctl_table; entry->procname; entry++)
erase_entry(head, entry);
}
static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
{
struct ctl_table *entry;
int err;
/* Is this a permanently empty directory? */
if (is_empty_dir(&dir->header))
return -EROFS;
/* Am I creating a permanently empty directory? */
if (header->ctl_table == sysctl_mount_point) {
if (!RB_EMPTY_ROOT(&dir->root))
return -EINVAL;
set_empty_dir(dir);
}
dir->header.nreg++;
header->parent = dir;
err = insert_links(header);
if (err)
goto fail_links;
for (entry = header->ctl_table; entry->procname; entry++) {
err = insert_entry(header, entry);
if (err)
goto fail;
}
return 0;
fail:
erase_header(header);
put_links(header);
fail_links:
if (header->ctl_table == sysctl_mount_point)
clear_empty_dir(dir);
header->parent = NULL;
drop_sysctl_table(&dir->header);
return err;
}
/* called under sysctl_lock */
static int use_table(struct ctl_table_header *p)
{
if (unlikely(p->unregistering))
return 0;
p->used++;
return 1;
}
/* called under sysctl_lock */
static void unuse_table(struct ctl_table_header *p)
{
if (!--p->used)
if (unlikely(p->unregistering))
complete(p->unregistering);
}
static void proc_sys_prune_dcache(struct ctl_table_header *head)
{
struct inode *inode;
struct proc_inode *ei;
struct hlist_node *node;
struct super_block *sb;
rcu_read_lock();
for (;;) {
node = hlist_first_rcu(&head->inodes);
if (!node)
break;
ei = hlist_entry(node, struct proc_inode, sysctl_inodes);
spin_lock(&sysctl_lock);
hlist_del_init_rcu(&ei->sysctl_inodes);
spin_unlock(&sysctl_lock);
inode = &ei->vfs_inode;
sb = inode->i_sb;
if (!atomic_inc_not_zero(&sb->s_active))
continue;
inode = igrab(inode);
rcu_read_unlock();
if (unlikely(!inode)) {
deactivate_super(sb);
rcu_read_lock();
continue;
}
d_prune_aliases(inode);
iput(inode);
deactivate_super(sb);
rcu_read_lock();
}
rcu_read_unlock();
}
/* called under sysctl_lock, will reacquire if has to wait */
static void start_unregistering(struct ctl_table_header *p)
{
/*
* if p->used is 0, nobody will ever touch that entry again;
* we'll eliminate all paths to it before dropping sysctl_lock
*/
if (unlikely(p->used)) {
struct completion wait;
init_completion(&wait);
p->unregistering = &wait;
spin_unlock(&sysctl_lock);
wait_for_completion(&wait);
} else {
/* anything non-NULL; we'll never dereference it */
p->unregistering = ERR_PTR(-EINVAL);
spin_unlock(&sysctl_lock);
}
/*
* Prune dentries for unregistered sysctls: namespaced sysctls
* can have duplicate names and contaminate dcache very badly.
*/
proc_sys_prune_dcache(p);
/*
* do not remove from the list until nobody holds it; walking the
* list in do_sysctl() relies on that.
*/
spin_lock(&sysctl_lock);
erase_header(p);
}
static struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *head)
{
BUG_ON(!head);
spin_lock(&sysctl_lock);
if (!use_table(head))
head = ERR_PTR(-ENOENT);
spin_unlock(&sysctl_lock);
return head;
}
static void sysctl_head_finish(struct ctl_table_header *head)
{
if (!head)
return;
spin_lock(&sysctl_lock);
unuse_table(head);
spin_unlock(&sysctl_lock);
}
static struct ctl_table_set *
lookup_header_set(struct ctl_table_root *root)
{
struct ctl_table_set *set = &root->default_set;
if (root->lookup)
set = root->lookup(root);
return set;
}
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;
spin_lock(&sysctl_lock);
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_node *first_usable_entry(struct rb_node *node)
{
struct ctl_node *ctl_node;
for (;node; node = rb_next(node)) {
ctl_node = rb_entry(node, struct ctl_node, node);
if (use_table(ctl_node->header))
return ctl_node;
}
return NULL;
}
static void first_entry(struct ctl_dir *dir,
struct ctl_table_header **phead, struct ctl_table **pentry)
{
struct ctl_table_header *head = NULL;
struct ctl_table *entry = NULL;
struct ctl_node *ctl_node;
spin_lock(&sysctl_lock);
ctl_node = first_usable_entry(rb_first(&dir->root));
spin_unlock(&sysctl_lock);
if (ctl_node) {
head = ctl_node->header;
entry = &head->ctl_table[ctl_node - head->node];
}
*phead = head;
*pentry = entry;
}
static void next_entry(struct ctl_table_header **phead, struct ctl_table **pentry)
{
struct ctl_table_header *head = *phead;
struct ctl_table *entry = *pentry;
struct ctl_node *ctl_node = &head->node[entry - head->ctl_table];
spin_lock(&sysctl_lock);
unuse_table(head);
ctl_node = first_usable_entry(rb_next(&ctl_node->node));
spin_unlock(&sysctl_lock);
head = NULL;
if (ctl_node) {
head = ctl_node->header;
entry = &head->ctl_table[ctl_node - head->node];
}
*phead = head;
*pentry = entry;
}
/*
* sysctl_perm does NOT grant the superuser all rights automatically, because
* some sysctl variables are readonly even to root.
*/
static int test_perm(int mode, int op)
{
if (uid_eq(current_euid(), GLOBAL_ROOT_UID))
mode >>= 6;
else if (in_egroup_p(GLOBAL_ROOT_GID))
mode >>= 3;
if ((op & ~mode & (MAY_READ|MAY_WRITE|MAY_EXEC)) == 0)
return 0;
return -EACCES;
}
static int sysctl_perm(struct ctl_table_header *head, struct ctl_table *table, int op)
{
struct ctl_table_root *root = head->root;
int mode;
if (root->permissions)
mode = root->permissions(head, table);
else
mode = table->mode;
return test_perm(mode, op);
}
static struct inode *proc_sys_make_inode(struct super_block *sb,
struct ctl_table_header *head, struct ctl_table *table)
{
struct ctl_table_root *root = head->root;
struct inode *inode;
struct proc_inode *ei;
inode = new_inode(sb);
if (!inode)
return ERR_PTR(-ENOMEM);
inode->i_ino = get_next_ino();
ei = PROC_I(inode);
spin_lock(&sysctl_lock);
if (unlikely(head->unregistering)) {
spin_unlock(&sysctl_lock);
iput(inode);
return ERR_PTR(-ENOENT);
}
ei->sysctl = head;
ei->sysctl_entry = table;
hlist_add_head_rcu(&ei->sysctl_inodes, &head->inodes);
head->count++;
spin_unlock(&sysctl_lock);
inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
inode->i_mode = table->mode;
if (!S_ISDIR(table->mode)) {
inode->i_mode |= S_IFREG;
inode->i_op = &proc_sys_inode_operations;
inode->i_fop = &proc_sys_file_operations;
} else {
inode->i_mode |= S_IFDIR;
inode->i_op = &proc_sys_dir_operations;
inode->i_fop = &proc_sys_dir_file_operations;
if (is_empty_dir(head))
make_empty_dir_inode(inode);
}
if (root->set_ownership)
root->set_ownership(head, table, &inode->i_uid, &inode->i_gid);
else {
inode->i_uid = GLOBAL_ROOT_UID;
inode->i_gid = GLOBAL_ROOT_GID;
}
return inode;
}
void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
{
spin_lock(&sysctl_lock);
hlist_del_init_rcu(&PROC_I(inode)->sysctl_inodes);
if (!--head->count)
kfree_rcu(head, rcu);
spin_unlock(&sysctl_lock);
}
static struct ctl_table_header *grab_header(struct inode *inode)
{
struct ctl_table_header *head = PROC_I(inode)->sysctl;
if (!head)
head = &sysctl_table_root.default_set.dir.header;
return sysctl_head_grab(head);
}
static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
struct ctl_table_header *head = grab_header(dir);
struct ctl_table_header *h = NULL;
const struct qstr *name = &dentry->d_name;
struct ctl_table *p;
struct inode *inode;
struct dentry *err = ERR_PTR(-ENOENT);
struct ctl_dir *ctl_dir;
int ret;
if (IS_ERR(head))
return ERR_CAST(head);
ctl_dir = container_of(head, struct ctl_dir, header);
p = lookup_entry(&h, ctl_dir, name->name, name->len);
if (!p)
goto out;
if (S_ISLNK(p->mode)) {
ret = sysctl_follow_link(&h, &p);
err = ERR_PTR(ret);
if (ret)
goto out;
}
inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
if (IS_ERR(inode)) {
err = ERR_CAST(inode);
goto out;
}
d_set_d_op(dentry, &proc_sys_dentry_operations);
err = d_splice_alias(inode, dentry);
out:
if (h)
sysctl_head_finish(h);
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 inode *inode = file_inode(filp);
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
void *new_buf = NULL;
ssize_t error;
if (IS_ERR(head))
return PTR_ERR(head);
/*
* At this point we know that the sysctl was not unregistered
* and won't be until we finish.
*/
error = -EPERM;
if (sysctl_perm(head, table, write ? MAY_WRITE : MAY_READ))
goto out;
/* if that can happen at all, it should be -EINVAL, not -EISDIR */
error = -EINVAL;
if (!table->proc_handler)
goto out;
error = BPF_CGROUP_RUN_PROG_SYSCTL(head, table, write, buf, &count,
ppos, &new_buf);
if (error)
goto out;
/* careful: calling conventions are nasty here */
if (new_buf) {
mm_segment_t old_fs;
old_fs = get_fs();
set_fs(KERNEL_DS);
error = table->proc_handler(table, write, (void __user *)new_buf,
&count, ppos);
set_fs(old_fs);
kfree(new_buf);
} else {
error = table->proc_handler(table, write, buf, &count, ppos);
}
if (!error)
error = count;
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_open(struct inode *inode, struct file *filp)
{
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
/* sysctl was unregistered */
if (IS_ERR(head))
return PTR_ERR(head);
if (table->poll)
filp->private_data = proc_sys_poll_event(table->poll);
sysctl_head_finish(head);
return 0;
}
static __poll_t proc_sys_poll(struct file *filp, poll_table *wait)
{
struct inode *inode = file_inode(filp);
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
__poll_t ret = DEFAULT_POLLMASK;
unsigned long event;
/* sysctl was unregistered */
if (IS_ERR(head))
return EPOLLERR | EPOLLHUP;
if (!table->proc_handler)
goto out;
if (!table->poll)
goto out;
event = (unsigned long)filp->private_data;
poll_wait(filp, &table->poll->wait, wait);
if (event != atomic_read(&table->poll->event)) {
filp->private_data = proc_sys_poll_event(table->poll);
ret = EPOLLIN | EPOLLRDNORM | EPOLLERR | EPOLLPRI;
}
out:
sysctl_head_finish(head);
return ret;
}
static bool proc_sys_fill_cache(struct file *file,
struct dir_context *ctx,
struct ctl_table_header *head,
struct ctl_table *table)
{
struct dentry *child, *dir = file->f_path.dentry;
struct inode *inode;
struct qstr qname;
ino_t ino = 0;
unsigned type = DT_UNKNOWN;
qname.name = table->procname;
qname.len = strlen(table->procname);
qname.hash = full_name_hash(dir, qname.name, qname.len);
child = d_lookup(dir, &qname);
if (!child) {
DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
child = d_alloc_parallel(dir, &qname, &wq);
if (IS_ERR(child))
return false;
if (d_in_lookup(child)) {
struct dentry *res;
inode = proc_sys_make_inode(dir->d_sb, head, table);
if (IS_ERR(inode)) {
d_lookup_done(child);
dput(child);
return false;
}
d_set_d_op(child, &proc_sys_dentry_operations);
res = d_splice_alias(inode, child);
d_lookup_done(child);
if (unlikely(res)) {
if (IS_ERR(res)) {
dput(child);
return false;
}
dput(child);
child = res;
}
}
}
inode = d_inode(child);
ino = inode->i_ino;
type = inode->i_mode >> 12;
dput(child);
return dir_emit(ctx, qname.name, qname.len, ino, type);
}
static bool proc_sys_link_fill_cache(struct file *file,
struct dir_context *ctx,
struct ctl_table_header *head,
struct ctl_table *table)
{
bool ret = true;
head = sysctl_head_grab(head);
if (IS_ERR(head))
return false;
/* It is not an error if we can not follow the link ignore it */
if (sysctl_follow_link(&head, &table))
goto out;
ret = proc_sys_fill_cache(file, ctx, head, table);
out:
sysctl_head_finish(head);
return ret;
}
static int scan(struct ctl_table_header *head, struct ctl_table *table,
unsigned long *pos, struct file *file,
struct dir_context *ctx)
{
bool res;
if ((*pos)++ < ctx->pos)
return true;
if (unlikely(S_ISLNK(table->mode)))
res = proc_sys_link_fill_cache(file, ctx, head, table);
else
res = proc_sys_fill_cache(file, ctx, head, table);
if (res)
ctx->pos = *pos;
return res;
}
static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
{
struct ctl_table_header *head = grab_header(file_inode(file));
struct ctl_table_header *h = NULL;
struct ctl_table *entry;
struct ctl_dir *ctl_dir;
unsigned long pos;
if (IS_ERR(head))
return PTR_ERR(head);
ctl_dir = container_of(head, struct ctl_dir, header);
if (!dir_emit_dots(file, ctx))
goto out;
pos = 2;
for (first_entry(ctl_dir, &h, &entry); h; next_entry(&h, &entry)) {
if (!scan(h, entry, &pos, file, ctx)) {
sysctl_head_finish(h);
break;
}
}
out:
sysctl_head_finish(head);
return 0;
}
static int proc_sys_permission(struct inode *inode, int mask)
{
/*
* sysctl entries that are not writeable,
* are _NOT_ writeable, capabilities or not.
*/
struct ctl_table_header *head;
struct ctl_table *table;
int error;
/* Executable files are not allowed under /proc/sys/ */
if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode))
return -EACCES;
head = grab_header(inode);
if (IS_ERR(head))
return PTR_ERR(head);
table = PROC_I(inode)->sysctl_entry;
if (!table) /* global root - r-xr-xr-x */
error = mask & MAY_WRITE ? -EACCES : 0;
else /* Use the permissions on the sysctl table entry */
error = sysctl_perm(head, table, mask & ~MAY_NOT_BLOCK);
sysctl_head_finish(head);
return error;
}
static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = d_inode(dentry);
int error;
if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
return -EPERM;
error = setattr_prepare(dentry, attr);
if (error)
return error;
setattr_copy(inode, attr);
mark_inode_dirty(inode);
return 0;
}
static int proc_sys_getattr(const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
struct inode *inode = d_inode(path->dentry);
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
if (IS_ERR(head))
return PTR_ERR(head);
generic_fillattr(inode, stat);
if (table)
stat->mode = (stat->mode & S_IFMT) | table->mode;
sysctl_head_finish(head);
return 0;
}
static const struct file_operations proc_sys_file_operations = {
.open = proc_sys_open,
.poll = proc_sys_poll,
.read = proc_sys_read,
.write = proc_sys_write,
.llseek = default_llseek,
};
static const struct file_operations proc_sys_dir_file_operations = {
.read = generic_read_dir,
.iterate_shared = proc_sys_readdir,
.llseek = generic_file_llseek,
};
static const struct inode_operations proc_sys_inode_operations = {
.permission = proc_sys_permission,
.setattr = proc_sys_setattr,
.getattr = proc_sys_getattr,
};
static const struct inode_operations proc_sys_dir_operations = {
.lookup = proc_sys_lookup,
.permission = proc_sys_permission,
.setattr = proc_sys_setattr,
.getattr = proc_sys_getattr,
};
static int proc_sys_revalidate(struct dentry *dentry, unsigned int flags)
{
if (flags & LOOKUP_RCU)
return -ECHILD;
return !PROC_I(d_inode(dentry))->sysctl->unregistering;
}
static int proc_sys_delete(const struct dentry *dentry)
{
return !!PROC_I(d_inode(dentry))->sysctl->unregistering;
}
static int sysctl_is_seen(struct ctl_table_header *p)
{
struct ctl_table_set *set = p->set;
int res;
spin_lock(&sysctl_lock);
if (p->unregistering)
res = 0;
else if (!set->is_seen)
res = 1;
else
res = set->is_seen(set);
spin_unlock(&sysctl_lock);
return res;
}
static int proc_sys_compare(const struct dentry *dentry,
unsigned int len, const char *str, const struct qstr *name)
{
struct ctl_table_header *head;
struct inode *inode;
/* Although proc doesn't have negative dentries, rcu-walk means
* that inode here can be NULL */
/* AV: can it, indeed? */
inode = d_inode_rcu(dentry);
if (!inode)
return 1;
if (name->len != len)
return 1;
if (memcmp(name->name, str, len))
return 1;
head = rcu_dereference(PROC_I(inode)->sysctl);
return !head || !sysctl_is_seen(head);
}
static const struct dentry_operations proc_sys_dentry_operations = {
.d_revalidate = proc_sys_revalidate,
.d_delete = proc_sys_delete,
.d_compare = proc_sys_compare,
};
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, dir, name, namelen);
if (!entry)
return ERR_PTR(-ENOENT);
if (!S_ISDIR(entry->mode))
return ERR_PTR(-ENOTDIR);
return container_of(head, struct ctl_dir, header);
}
static struct ctl_dir *new_dir(struct ctl_table_set *set,
const char *name, int namelen)
{
struct ctl_table *table;
struct ctl_dir *new;
struct ctl_node *node;
char *new_name;
new = kzalloc(sizeof(*new) + sizeof(struct ctl_node) +
sizeof(struct ctl_table)*2 + namelen + 1,
GFP_KERNEL);
if (!new)
return NULL;
node = (struct ctl_node *)(new + 1);
table = (struct ctl_table *)(node + 1);
new_name = (char *)(table + 2);
memcpy(new_name, name, namelen);
new_name[namelen] = '\0';
table[0].procname = new_name;
table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
init_header(&new->header, set->dir.header.root, set, node, table);
return new;
}
/**
* get_subdir - find or create a subdir with the specified name.
* @dir: Directory to create the subdirectory in
* @name: The name of the subdirectory to find or create
* @namelen: The length of name
*
* Takes a directory with an elevated reference count so we know that
* if we drop the lock the directory will not go away. Upon success
* the reference is moved from @dir to the returned subdirectory.
* Upon error an error code is returned and the reference on @dir is
* simply dropped.
*/
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;
int err;
spin_lock(&sysctl_lock);
subdir = find_subdir(dir, name, namelen);
if (!IS_ERR(subdir))
goto found;
if (PTR_ERR(subdir) != -ENOENT)
goto failed;
spin_unlock(&sysctl_lock);
new = new_dir(set, name, namelen);
spin_lock(&sysctl_lock);
subdir = ERR_PTR(-ENOMEM);
if (!new)
goto failed;
/* Was the subdir added while we dropped the lock? */
subdir = find_subdir(dir, name, namelen);
if (!IS_ERR(subdir))
goto found;
if (PTR_ERR(subdir) != -ENOENT)
goto failed;
/* Nope. Use the our freshly made directory entry. */
err = insert_header(dir, &new->header);
subdir = ERR_PTR(err);
if (err)
goto failed;
subdir = new;
found:
subdir->header.nreg++;
failed:
if (IS_ERR(subdir)) {
pr_err("sysctl could not get directory: ");
sysctl_print_dir(dir);
pr_cont("/%*.*s %ld\n",
namelen, namelen, name, PTR_ERR(subdir));
}
drop_sysctl_table(&dir->header);
if (new)
drop_sysctl_table(&new->header);
spin_unlock(&sysctl_lock);
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 ctl_table_header *head;
struct ctl_table_root *root;
struct ctl_table_set *set;
struct ctl_table *entry;
struct ctl_dir *dir;
int ret;
ret = 0;
spin_lock(&sysctl_lock);
root = (*pentry)->data;
set = lookup_header_set(root);
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_err(const char *path, struct ctl_table *table, char *fmt, ...)
{
struct va_format vaf;
va_list args;
va_start(args, fmt);
vaf.fmt = fmt;
vaf.va = &args;
pr_err("sysctl table check failed: %s/%s %pV\n",
path, table->procname, &vaf);
va_end(args);
return -EINVAL;
}
static int sysctl_check_table_array(const char *path, struct ctl_table *table)
{
int err = 0;
if ((table->proc_handler == proc_douintvec) ||
(table->proc_handler == proc_douintvec_minmax)) {
if (table->maxlen != sizeof(unsigned int))
err |= sysctl_err(path, table, "array not allowed");
}
return err;
}
static int sysctl_check_table(const char *path, struct ctl_table *table)
{
int err = 0;
for (; table->procname; table++) {
if (table->child)
err |= sysctl_err(path, table, "Not a file");
if ((table->proc_handler == proc_dostring) ||
(table->proc_handler == proc_dointvec) ||
(table->proc_handler == proc_douintvec) ||
(table->proc_handler == proc_douintvec_minmax) ||
(table->proc_handler == proc_dointvec_minmax) ||
(table->proc_handler == proc_dointvec_jiffies) ||
(table->proc_handler == proc_dointvec_userhz_jiffies) ||
(table->proc_handler == proc_dointvec_ms_jiffies) ||
(table->proc_handler == proc_doulongvec_minmax) ||
(table->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
if (!table->data)
err |= sysctl_err(path, table, "No data");
if (!table->maxlen)
err |= sysctl_err(path, table, "No maxlen");
else
err |= sysctl_check_table_array(path, table);
}
if (!table->proc_handler)
err |= sysctl_err(path, table, "No proc_handler");
if ((table->mode & (S_IRUGO|S_IWUGO)) != table->mode)
err |= sysctl_err(path, table, "bogus .mode 0%o",
table->mode);
}
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;
struct ctl_node *node;
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_node)*nr_entries +
sizeof(struct ctl_table)*(nr_entries + 1) +
name_bytes,
GFP_KERNEL);
if (!links)
return NULL;
node = (struct ctl_node *)(links + 1);
link_table = (struct ctl_table *)(node + nr_entries);
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, node, 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
* @set: Sysctl tree to register on
* @path: The path to the directory the sysctl table is in.
* @table: the top-level table structure
*
* Register a sysctl table hierarchy. @table should be a filled in ctl_table
* array. A completely 0 filled entry terminates the table.
*
* The members of the &struct ctl_table structure are used as follows:
*
* procname - the name of the sysctl file under /proc/sys. Set to %NULL to not
* enter a sysctl file
*
* data - a pointer to data for use by proc_handler
*
* maxlen - the maximum size in bytes of the data
*
* mode - the file permissions for the /proc/sys file
*
* child - must be %NULL.
*
* proc_handler - the text handler routine (described below)
*
* extra1, extra2 - extra pointers usable by the proc handler routines
*
* Leaf nodes in the sysctl tree will be represented by a single file
* under /proc; non-leaf nodes will be represented by directories.
*
* There must be a proc_handler routine for any terminal nodes.
* Several default handlers are available to cover common cases -
*
* proc_dostring(), proc_dointvec(), proc_dointvec_jiffies(),
* proc_dointvec_userhz_jiffies(), proc_dointvec_minmax(),
* proc_doulongvec_ms_jiffies_minmax(), proc_doulongvec_minmax()
*
* It is the handler's job to read the input buffer from user memory
* and process it. The handler should return 0 on success.
*
* This routine returns %NULL on a failure to register, and a pointer
* to the table header on success.
*/
struct ctl_table_header *__register_sysctl_table(
struct ctl_table_set *set,
const char *path, struct ctl_table *table)
{
struct ctl_table_root *root = set->dir.header.root;
struct ctl_table_header *header;
const char *name, *nextname;
struct ctl_dir *dir;
struct ctl_table *entry;
struct ctl_node *node;
int nr_entries = 0;
for (entry = table; entry->procname; entry++)
nr_entries++;
header = kzalloc(sizeof(struct ctl_table_header) +
sizeof(struct ctl_node)*nr_entries, GFP_KERNEL);
if (!header)
return NULL;
node = (struct ctl_node *)(header + 1);
init_header(header, root, set, node, table);
if (sysctl_check_table(path, table))
goto fail;
spin_lock(&sysctl_lock);
dir = &set->dir;
/* Reference moved down the diretory tree get_subdir */
dir->header.nreg++;
spin_unlock(&sysctl_lock);
/* Find the directory for the ctl_table */
for (name = path; name; name = nextname) {
int namelen;
nextname = strchr(name, '/');
if (nextname) {
namelen = nextname - name;
nextname++;
} else {
namelen = strlen(name);
}
if (namelen == 0)
continue;
dir = get_subdir(dir, name, namelen);
if (IS_ERR(dir))
goto fail;
}
spin_lock(&sysctl_lock);
if (insert_header(dir, header))
goto fail_put_dir_locked;
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(header);
dump_stack();
return NULL;
}
/**
* register_sysctl - register a sysctl table
* @path: The path to the directory the sysctl table is in.
* @table: the table structure
*
* Register a sysctl table. @table should be a filled in ctl_table
* array. A completely 0 filled entry terminates the table.
*
* See __register_sysctl_table for more details.
*/
struct ctl_table_header *register_sysctl(const char *path, struct ctl_table *table)
{
return __register_sysctl_table(&sysctl_table_root.default_set,
path, table);
}
EXPORT_SYMBOL(register_sysctl);
static char *append_path(const char *path, char *pos, const char *name)
{
int namelen;
namelen = strlen(name);
if (((pos - path) + namelen + 2) >= PATH_MAX)
return NULL;
memcpy(pos, name, namelen);
pos[namelen] = '/';
pos[namelen + 1] = '\0';
pos += namelen + 1;
return pos;
}
static int count_subheaders(struct ctl_table *table)
{
int has_files = 0;
int nr_subheaders = 0;
struct ctl_table *entry;
/* special case: no directory and empty directory */
if (!table || !table->procname)
return 1;
for (entry = table; entry->procname; entry++) {
if (entry->child)
nr_subheaders += count_subheaders(entry->child);
else
has_files = 1;
}
return nr_subheaders + has_files;
}
static int register_leaf_sysctl_tables(const char *path, char *pos,
struct ctl_table_header ***subheader, struct ctl_table_set *set,
struct ctl_table *table)
{
struct ctl_table *ctl_table_arg = NULL;
struct ctl_table *entry, *files;
int nr_files = 0;
int nr_dirs = 0;
int err = -ENOMEM;
for (entry = table; entry->procname; entry++) {
if (entry->child)
nr_dirs++;
else
nr_files++;
}
files = table;
/* If there are mixed files and directories we need a new table */
if (nr_dirs && nr_files) {
struct ctl_table *new;
files = kcalloc(nr_files + 1, sizeof(struct ctl_table),
GFP_KERNEL);
if (!files)
goto out;
ctl_table_arg = files;
for (new = files, entry = table; entry->procname; entry++) {
if (entry->child)
continue;
*new = *entry;
new++;
}
}
/* Register everything except a directory full of subdirectories */
if (nr_files || !nr_dirs) {
struct ctl_table_header *header;
header = __register_sysctl_table(set, path, files);
if (!header) {
kfree(ctl_table_arg);
goto out;
}
/* Remember if we need to free the file table */
header->ctl_table_arg = ctl_table_arg;
**subheader = header;
(*subheader)++;
}
/* Recurse into the subdirectories. */
for (entry = table; entry->procname; entry++) {
char *child_pos;
if (!entry->child)
continue;
err = -ENAMETOOLONG;
child_pos = append_path(path, pos, entry->procname);
if (!child_pos)
goto out;
err = register_leaf_sysctl_tables(path, child_pos, subheader,
set, entry->child);
pos[0] = '\0';
if (err)
goto out;
}
err = 0;
out:
/* On failure our caller will unregister all registered subheaders */
return err;
}
/**
* __register_sysctl_paths - register a sysctl table hierarchy
* @set: Sysctl tree to register on
* @path: The path to the directory the sysctl table is in.
* @table: the top-level table structure
*
* Register a sysctl table hierarchy. @table should be a filled in ctl_table
* array. A completely 0 filled entry terminates the table.
*
* See __register_sysctl_table for more details.
*/
struct ctl_table_header *__register_sysctl_paths(
struct ctl_table_set *set,
const struct ctl_path *path, struct ctl_table *table)
{
struct ctl_table *ctl_table_arg = table;
int nr_subheaders = count_subheaders(table);
struct ctl_table_header *header = NULL, **subheaders, **subheader;
const struct ctl_path *component;
char *new_path, *pos;
pos = new_path = kmalloc(PATH_MAX, GFP_KERNEL);
if (!new_path)
return NULL;
pos[0] = '\0';
for (component = path; component->procname; component++) {
pos = append_path(new_path, pos, component->procname);
if (!pos)
goto out;
}
while (table->procname && table->child && !table[1].procname) {
pos = append_path(new_path, pos, table->procname);
if (!pos)
goto out;
table = table->child;
}
if (nr_subheaders == 1) {
header = __register_sysctl_table(set, new_path, table);
if (header)
header->ctl_table_arg = ctl_table_arg;
} else {
header = kzalloc(sizeof(*header) +
sizeof(*subheaders)*nr_subheaders, GFP_KERNEL);
if (!header)
goto out;
subheaders = (struct ctl_table_header **) (header + 1);
subheader = subheaders;
header->ctl_table_arg = ctl_table_arg;
if (register_leaf_sysctl_tables(new_path, pos, &subheader,
set, table))
goto err_register_leaves;
}
out:
kfree(new_path);
return header;
err_register_leaves:
while (subheader > subheaders) {
struct ctl_table_header *subh = *(--subheader);
struct ctl_table *table = subh->ctl_table_arg;
unregister_sysctl_table(subh);
kfree(table);
}
kfree(header);
header = NULL;
goto out;
}
/**
* register_sysctl_table_path - register a sysctl table hierarchy
* @path: The path to the directory the sysctl table is in.
* @table: the top-level table structure
*
* Register a sysctl table hierarchy. @table should be a filled in ctl_table
* array. A completely 0 filled entry terminates the table.
*
* See __register_sysctl_paths for more details.
*/
struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
struct ctl_table *table)
{
return __register_sysctl_paths(&sysctl_table_root.default_set,
path, table);
}
EXPORT_SYMBOL(register_sysctl_paths);
/**
* register_sysctl_table - register a sysctl table hierarchy
* @table: the top-level table structure
*
* Register a sysctl table hierarchy. @table should be a filled in ctl_table
* array. A completely 0 filled entry terminates the table.
*
* See register_sysctl_paths for more details.
*/
struct ctl_table_header *register_sysctl_table(struct ctl_table *table)
{
static const struct ctl_path null_path[] = { {} };
return register_sysctl_paths(null_path, 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 {
pr_err("sysctl link missing during unregister: ");
sysctl_print_dir(parent);
pr_cont("/%s\n", name);
}
}
}
static void drop_sysctl_table(struct ctl_table_header *header)
{
struct ctl_dir *parent = header->parent;
if (--header->nreg)
return;
if (parent) {
put_links(header);
start_unregistering(header);
}
if (!--header->count)
kfree_rcu(header, rcu);
if (parent)
drop_sysctl_table(&parent->header);
}
/**
* unregister_sysctl_table - unregister a sysctl table hierarchy
* @header: the header returned from register_sysctl_table
*
* Unregisters the sysctl table and all children. proc entries may not
* actually be removed until they are no longer used by anyone.
*/
void unregister_sysctl_table(struct ctl_table_header * header)
{
int nr_subheaders;
might_sleep();
if (header == NULL)
return;
nr_subheaders = count_subheaders(header->ctl_table_arg);
if (unlikely(nr_subheaders > 1)) {
struct ctl_table_header **subheaders;
int i;
subheaders = (struct ctl_table_header **)(header + 1);
for (i = nr_subheaders -1; i >= 0; i--) {
struct ctl_table_header *subh = subheaders[i];
struct ctl_table *table = subh->ctl_table_arg;
unregister_sysctl_table(subh);
kfree(table);
}
kfree(header);
return;
}
spin_lock(&sysctl_lock);
drop_sysctl_table(header);
spin_unlock(&sysctl_lock);
}
EXPORT_SYMBOL(unregister_sysctl_table);
void setup_sysctl_set(struct ctl_table_set *set,
struct ctl_table_root *root,
int (*is_seen)(struct ctl_table_set *))
{
memset(set, 0, sizeof(*set));
set->is_seen = is_seen;
init_header(&set->dir.header, root, set, NULL, root_table);
}
void retire_sysctl_set(struct ctl_table_set *set)
{
WARN_ON(!RB_EMPTY_ROOT(&set->dir.root));
}
int __init proc_sys_init(void)
{
struct proc_dir_entry *proc_sys_root;
proc_sys_root = proc_mkdir("sys", NULL);
proc_sys_root->proc_iops = &proc_sys_dir_operations;
proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
proc_sys_root->nlink = 0;
return sysctl_init();
}