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[PATCH] sanitize proc_sysctl 

* keep references to ctl_table_head and ctl_table in /proc/sys inodes
* grab the former during operations, use the latter for access to
  entry if that succeeds
* have ->d_compare() check if table should be seen for one who does lookup;
  that allows us to avoid flipping inodes - if we have the same name resolve
  to different things, we'll just keep several dentries and ->d_compare()
  will reject the wrong ones.
* have ->lookup() and ->readdir() scan the table of our inode first, then
  walk all ctl_table_header and scan ->attached_by for those that are
  attached to our directory.
* implement ->getattr().
* get rid of insane amounts of tree-walking
* get rid of the need to know dentry in ->permission() and of the contortions
  induced by that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2008-07-15 08:54:06 -04:00
parent ae7edecc9b
commit 9043476f72
5 changed files with 219 additions and 236 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
fs/proc/inode.c
View File

@ -17,6 +17,7 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/sysctl.h>
#include <asm/system.h>
#include <asm/uaccess.h>
@ -65,6 +66,8 @@ static void proc_delete_inode(struct inode *inode)
module_put(de->owner);
de_put(de);
}
if (PROC_I(inode)->sysctl)
sysctl_head_put(PROC_I(inode)->sysctl);
clear_inode(inode);
}
@ -84,6 +87,8 @@ static struct inode *proc_alloc_inode(struct super_block *sb)
ei->fd = 0;
ei->op.proc_get_link = NULL;
ei->pde = NULL;
ei->sysctl = NULL;
ei->sysctl_entry = NULL;
inode = &ei->vfs_inode;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
return inode;

425
fs/proc/proc_sysctl.c
View File

@ -10,149 +10,110 @@
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 const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_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)
static struct inode *proc_sys_make_inode(struct super_block *sb,
struct ctl_table_header *head, struct ctl_table *table)
{
struct inode *inode;
struct proc_inode *dir_ei, *ei;
int depth;
struct proc_inode *ei;
inode = new_inode(dir->i_sb);
inode = new_inode(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;
sysctl_head_get(head);
ei = PROC_I(inode);
ei->fd = depth;
ei->sysctl = head;
ei->sysctl_entry = table;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
inode->i_mode = table->mode;
if (!table->child) {
inode->i_mode |= S_IFREG;
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);
} else {
inode->i_mode |= S_IFDIR;
inode->i_nlink = 0;
inode->i_op = &proc_sys_dir_operations;
inode->i_fop = &proc_sys_dir_file_operations;
}
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)
static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)
{
int len;
for ( ; table->ctl_name || table->procname; table++) {
for ( ; p->ctl_name || p->procname; p++) {
if (!table->procname)
if (!p->procname)
continue;
len = strlen(table->procname);
len = strlen(p->procname);
if (len != name->len)
continue;
if (memcmp(table->procname, name->name, len) != 0)
if (memcmp(p->procname, name->name, len) != 0)
continue;
/* I have a match */
return table;
return p;
}
return NULL;
}
static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry,
struct ctl_table *table)
struct ctl_table_header *grab_header(struct inode *inode)
{
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;
if (PROC_I(inode)->sysctl)
return sysctl_head_grab(PROC_I(inode)->sysctl);
else
return sysctl_head_next(NULL);
}
static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
struct ctl_table_header *head;
struct ctl_table_header *head = grab_header(dir);
struct ctl_table *table = PROC_I(dir)->sysctl_entry;
struct ctl_table_header *h = NULL;
struct qstr *name = &dentry->d_name;
struct ctl_table *p;
struct inode *inode;
struct dentry *err;
struct ctl_table *table;
struct dentry *err = ERR_PTR(-ENOENT);
err = ERR_PTR(-ENOENT);
table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
if (!table)
if (IS_ERR(head))
return ERR_CAST(head);
if (table && !table->child) {
WARN_ON(1);
goto out;
}
table = table ? table->child : head->ctl_table;
p = find_in_table(table, name);
if (!p) {
for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
if (h->attached_to != table)
continue;
p = find_in_table(h->attached_by, name);
if (p)
break;
}
}
if (!p)
goto out;
err = ERR_PTR(-ENOMEM);
inode = proc_sys_make_inode(dir, table);
inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
if (h)
sysctl_head_finish(h);
if (!inode)
goto out;
@ -168,22 +129,14 @@ out:
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;
struct inode *inode = filp->f_path.dentry->d_inode;
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
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;
if (IS_ERR(head))
return PTR_ERR(head);
/*
* At this point we know that the sysctl was not unregistered
@ -193,6 +146,11 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
if (sysctl_perm(head->root, 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;
/* careful: calling conventions are nasty here */
res = count;
error = table->proc_handler(table, write, filp, buf, &res, ppos);
@ -218,82 +176,86 @@ static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
static int proc_sys_fill_cache(struct file *filp, void *dirent,
filldir_t filldir, struct ctl_table *table)
filldir_t filldir,
struct ctl_table_header *head,
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);
child = d_alloc(dir, &qname);
if (child) {
inode = proc_sys_make_inode(dir->d_sb, head, table);
if (!inode) {
dput(child);
return -ENOMEM;
} else {
child->d_op = &proc_sys_dentry_operations;
d_add(child, inode);
}
if (child)
dput(new);
else
child = new;
} else {
return -ENOMEM;
}
}
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);
return !!filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
}
static int scan(struct ctl_table_header *head, ctl_table *table,
unsigned long *pos, struct file *file,
void *dirent, filldir_t filldir)
{
for (; table->ctl_name || table->procname; table++, (*pos)++) {
int res;
/* Can't do anything without a proc name */
if (!table->procname)
continue;
if (*pos < file->f_pos)
continue;
res = proc_sys_fill_cache(file, dirent, filldir, head, table);
if (res)
return res;
file->f_pos = *pos + 1;
}
return 0;
}
static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct dentry *dentry = filp->f_dentry;
struct dentry *dentry = filp->f_path.dentry;
struct inode *inode = dentry->d_inode;
struct ctl_table_header *head = NULL;
struct ctl_table *table;
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
struct ctl_table_header *h = NULL;
unsigned long pos;
int ret;
int ret = -EINVAL;
ret = -ENOTDIR;
if (!S_ISDIR(inode->i_mode))
if (IS_ERR(head))
return PTR_ERR(head);
if (table && !table->child) {
WARN_ON(1);
goto out;
}
table = table ? table->child : head->ctl_table;
ret = 0;
/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
@ -311,30 +273,17 @@ static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
}
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)
ret = scan(head, table, &pos, filp, dirent, filldir);
if (ret)
goto out;
filp->f_pos = pos + 1;
for (h = sysctl_head_next(NULL); h; h = sysctl_head_next(h)) {
if (h->attached_to != table)
continue;
ret = scan(h, h->attached_by, &pos, filp, dirent, filldir);
if (ret) {
sysctl_head_finish(h);
break;
}
}
ret = 1;
@ -349,47 +298,18 @@ static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *
* 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;
struct ctl_table_header *head = grab_header(inode);
struct ctl_table *table = PROC_I(inode)->sysctl_entry;
int error;
head = NULL;
depth = PROC_I(inode)->fd;
if (IS_ERR(head))
return PTR_ERR(head);
/* 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 */
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->root, table, mask);
out:
sysctl_head_finish(head);
return error;
}
@ -409,33 +329,70 @@ static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
return error;
}
/* I'm lazy and don't distinguish between files and directories,
* until access time.
*/
static int proc_sys_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
struct inode *inode = dentry->d_inode;
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 = {
.read = proc_sys_read,
.write = proc_sys_write,
};
static const struct file_operations proc_sys_dir_file_operations = {
.readdir = proc_sys_readdir,
};
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, 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;
return !PROC_I(dentry->d_inode)->sysctl->unregistering;
}
static int proc_sys_delete(struct dentry *dentry)
{
return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
}
static int proc_sys_compare(struct dentry *dir, struct qstr *qstr,
struct qstr *name)
{
struct dentry *dentry = container_of(qstr, struct dentry, d_name);
if (qstr->len != name->len)
return 1;
if (memcmp(qstr->name, name->name, name->len))
return 1;
return !sysctl_is_seen(PROC_I(dentry->d_inode)->sysctl);
}
static struct dentry_operations proc_sys_dentry_operations = {
.d_revalidate = proc_sys_revalidate,
.d_delete = proc_sys_delete,
.d_compare = proc_sys_compare,
};
static struct proc_dir_entry *proc_sys_root;
@ -443,8 +400,8 @@ 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->proc_iops = &proc_sys_dir_operations;
proc_sys_root->proc_fops = &proc_sys_dir_file_operations;
proc_sys_root->nlink = 0;
return 0;
}

5
include/linux/proc_fs.h
View File

@ -282,11 +282,16 @@ union proc_op {
struct task_struct *task);
};
struct ctl_table_header;
struct ctl_table;
struct proc_inode {
struct pid *pid;
int fd;
union proc_op op;
struct proc_dir_entry *pde;
struct ctl_table_header *sysctl;
struct ctl_table *sysctl_entry;
struct inode vfs_inode;
};

1
include/linux/sysctl.h
View File

@ -961,6 +961,7 @@ struct ctl_table_header;
extern void sysctl_head_get(struct ctl_table_header *);
extern void sysctl_head_put(struct ctl_table_header *);
extern int sysctl_is_seen(struct ctl_table_header *);
extern struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *);
extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev);
extern struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces,

15
kernel/sysctl.c
View File

@ -1932,6 +1932,21 @@ void unregister_sysctl_table(struct ctl_table_header * header)
spin_unlock(&sysctl_lock);
}
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;
}
void setup_sysctl_set(struct ctl_table_set *p,
struct ctl_table_set *parent,
int (*is_seen)(struct ctl_table_set *))