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/*
* binfmt_misc.c
*
* Copyright (C) 1997 Richard Günther
*
* binfmt_misc detects binaries via a magic or filename extension and invokes
* a specified wrapper. This should obsolete binfmt_java, binfmt_em86 and
* binfmt_mz.
*
* 1997-04-25 first version
* [...]
* 1997-05-19 cleanup
* 1997-06-26 hpa: pass the real filename rather than argv[0]
* 1997-06-30 minor cleanup
* 1997-08-09 removed extension stripping, locking cleanup
* 2001-02-28 AV: rewritten into something that resembles C. Original didn't.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/binfmts.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <asm/uaccess.h>
enum {
VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
};
static LIST_HEAD(entries);
static int enabled = 1;
enum {Enabled, Magic};
typedef struct {
struct list_head list;
int flags; /* type, status, etc. */
int offset; /* offset of magic */
int size; /* size of magic/mask */
char *magic; /* magic or filename extension */
char *mask; /* mask, NULL for exact match */
char *interpreter; /* filename of interpreter */
char *name;
struct dentry *dentry;
} Node;
static rwlock_t entries_lock __attribute__((unused)) = RW_LOCK_UNLOCKED;
/*
* Check if we support the binfmt
* if we do, return the node, else NULL
* locking is done in load_misc_binary
*/
static Node *check_file(struct linux_binprm *bprm)
{
char *p = strrchr(bprm->filename, '.');
struct list_head *l;
for (l = entries.next; l != &entries; l = l->next) {
Node *e = list_entry(l, Node, list);
char *s;
int j;
if (!test_bit(Enabled, &e->flags))
continue;
if (!test_bit(Magic, &e->flags)) {
if (p && !strcmp(e->magic, p + 1))
return e;
continue;
}
s = bprm->buf + e->offset;
if (e->mask) {
for (j = 0; j < e->size; j++)
if ((*s++ ^ e->magic[j]) & e->mask[j])
break;
} else {
for (j = 0; j < e->size; j++)
if ((*s++ ^ e->magic[j]))
break;
}
if (j == e->size)
return e;
}
return NULL;
}
/*
* the loader itself
*/
static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
{
Node *fmt;
struct file * file;
char iname[BINPRM_BUF_SIZE];
char *iname_addr = iname;
int retval;
retval = -ENOEXEC;
if (!enabled)
goto _ret;
/* to keep locking time low, we copy the interpreter string */
read_lock(&entries_lock);
fmt = check_file(bprm);
if (fmt) {
strncpy(iname, fmt->interpreter, BINPRM_BUF_SIZE - 1);
iname[BINPRM_BUF_SIZE - 1] = '\0';
}
read_unlock(&entries_lock);
if (!fmt)
goto _ret;
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
/* Build args for interpreter */
remove_arg_zero(bprm);
retval = copy_strings_kernel(1, &bprm->filename, bprm);
if (retval < 0) goto _ret;
bprm->argc++;
retval = copy_strings_kernel(1, &iname_addr, bprm);
if (retval < 0) goto _ret;
bprm->argc++;
bprm->filename = iname; /* for binfmt_script */
file = open_exec(iname);
retval = PTR_ERR(file);
if (IS_ERR(file))
goto _ret;
bprm->file = file;
retval = prepare_binprm(bprm);
if (retval >= 0)
retval = search_binary_handler(bprm, regs);
_ret:
return retval;
}
/* Command parsers */
/*
* parses and copies one argument enclosed in del from *sp to *dp,
* recognising the \x special.
* returns pointer to the copied argument or NULL in case of an
* error (and sets err) or null argument length.
*/
static char *scanarg(char *s, char del)
{
char c;
while ((c = *s++) != del) {
if (c == '\\' && *s == 'x') {
s++;
if (!isxdigit(*s++))
return NULL;
if (!isxdigit(*s++))
return NULL;
}
}
return s;
}
static int unquote(char *from)
{
char c = 0, *s = from, *p = from;
while ((c = *s++) != '\0') {
if (c == '\\' && *s == 'x') {
s++;
c = toupper(*s++);
*p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
c = toupper(*s++);
*p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
continue;
}
*p++ = c;
}
return p - from;
}
/*
* This registers a new binary format, it recognises the syntax
* ':name:type:offset:magic:mask:interpreter:'
* where the ':' is the IFS, that can be chosen with the first char
*/
static Node *create_entry(const char *buffer, size_t count)
{
Node *e;
int memsize, err;
char *buf, *p;
char del;
/* some sanity checks */
err = -EINVAL;
if ((count < 11) || (count > 256))
goto out;
err = -ENOMEM;
memsize = sizeof(Node) + count + 8;
e = (Node *) kmalloc(memsize, GFP_USER);
if (!e)
goto out;
p = buf = (char *)e + sizeof(Node);
memset(e, 0, sizeof(Node));
if (copy_from_user(buf, buffer, count))
goto Efault;
del = *p++; /* delimeter */
memset(buf+count, del, 8);
e->name = p;
p = strchr(p, del);
if (!p)
goto Einval;
*p++ = '\0';
if (!e->name[0] ||
!strcmp(e->name, ".") ||
!strcmp(e->name, "..") ||
strchr(e->name, '/'))
goto Einval;
switch (*p++) {
case 'E': e->flags = 1<<Enabled; break;
case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
default: goto Einval;
}
if (*p++ != del)
goto Einval;
if (test_bit(Magic, &e->flags)) {
char *s = strchr(p, del);
if (!s)
goto Einval;
*s++ = '\0';
e->offset = simple_strtoul(p, &p, 10);
if (*p++)
goto Einval;
e->magic = p;
p = scanarg(p, del);
if (!p)
goto Einval;
p[-1] = '\0';
if (!e->magic[0])
goto Einval;
e->mask = p;
p = scanarg(p, del);
if (!p)
goto Einval;
p[-1] = '\0';
if (!e->mask[0])
e->mask = NULL;
e->size = unquote(e->magic);
if (e->mask && unquote(e->mask) != e->size)
goto Einval;
if (e->size + e->offset > BINPRM_BUF_SIZE)
goto Einval;
} else {
p = strchr(p, del);
if (!p)
goto Einval;
*p++ = '\0';
e->magic = p;
p = strchr(p, del);
if (!p)
goto Einval;
*p++ = '\0';
if (!e->magic[0] || strchr(e->magic, '/'))
goto Einval;
p = strchr(p, del);
if (!p)
goto Einval;
*p++ = '\0';
}
e->interpreter = p;
p = strchr(p, del);
if (!p)
goto Einval;
*p++ = '\0';
if (!e->interpreter[0])
goto Einval;
if (*p == '\n')
p++;
if (p != buf + count)
goto Einval;
return e;
out:
return ERR_PTR(err);
Efault:
kfree(e);
return ERR_PTR(-EFAULT);
Einval:
kfree(e);
return ERR_PTR(-EINVAL);
}
/*
* Set status of entry/binfmt_misc:
* '1' enables, '0' disables and '-1' clears entry/binfmt_misc
*/
static int parse_command(const char *buffer, size_t count)
{
char s[4];
if (!count)
return 0;
if (count > 3)
return -EINVAL;
if (copy_from_user(s, buffer, count))
return -EFAULT;
if (s[count-1] == '\n')
count--;
if (count == 1 && s[0] == '0')
return 1;
if (count == 1 && s[0] == '1')
return 2;
if (count == 2 && s[0] == '-' && s[1] == '1')
return 3;
return -EINVAL;
}
/* generic stuff */
static void entry_status(Node *e, char *page)
{
char *dp;
char *status = "disabled";
if (test_bit(Enabled, &e->flags))
status = "enabled";
if (!VERBOSE_STATUS) {
sprintf(page, "%s\n", status);
return;
}
sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
dp = page + strlen(page);
if (!test_bit(Magic, &e->flags)) {
sprintf(dp, "extension .%s\n", e->magic);
} else {
int i;
sprintf(dp, "offset %i\nmagic ", e->offset);
dp = page + strlen(page);
for (i = 0; i < e->size; i++) {
sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
dp += 2;
}
if (e->mask) {
sprintf(dp, "\nmask ");
dp += 6;
for (i = 0; i < e->size; i++) {
sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
dp += 2;
}
}
*dp++ = '\n';
*dp = '\0';
}
}
static struct inode *bm_get_inode(struct super_block *sb, int mode)
{
struct inode * inode = new_inode(sb);
if (inode) {
inode->i_mode = mode;
inode->i_uid = 0;
inode->i_gid = 0;
inode->i_blksize = PAGE_CACHE_SIZE;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
}
return inode;
}
static void bm_clear_inode(struct inode *inode)
{
Node *e = inode->u.generic_ip;
if (e) {
write_lock(&entries_lock);
list_del(&e->list);
write_unlock(&entries_lock);
kfree(e);
}
}
static void kill_node(Node *e)
{
struct dentry *dentry;
write_lock(&entries_lock);
dentry = e->dentry;
if (dentry) {
list_del(&e->list);
INIT_LIST_HEAD(&e->list);
e->dentry = NULL;
}
write_unlock(&entries_lock);
if (dentry) {
dentry->d_inode->i_nlink--;
d_drop(dentry);
dput(dentry);
}
}
/* /<entry> */
static ssize_t
bm_entry_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
{
Node *e = file->f_dentry->d_inode->u.generic_ip;
loff_t pos = *ppos;
ssize_t res;
char *page;
int len;
if (!(page = (char*) __get_free_page(GFP_KERNEL)))
return -ENOMEM;
entry_status(e, page);
len = strlen(page);
res = -EINVAL;
if (pos < 0)
goto out;
res = 0;
if (pos >= len)
goto out;
if (len < pos + nbytes)
nbytes = len - pos;
res = -EFAULT;
if (copy_to_user(buf, page + pos, nbytes))
goto out;
*ppos = pos + nbytes;
res = nbytes;
out:
free_page((unsigned long) page);
return res;
}
static ssize_t bm_entry_write(struct file *file, const char *buffer,
size_t count, loff_t *ppos)
{
struct dentry *root;
Node *e = file->f_dentry->d_inode->u.generic_ip;
int res = parse_command(buffer, count);
switch (res) {
case 1: clear_bit(Enabled, &e->flags);
break;
case 2: set_bit(Enabled, &e->flags);
break;
case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
down(&root->d_inode->i_sem);
down(&root->d_inode->i_zombie);
kill_node(e);
up(&root->d_inode->i_zombie);
up(&root->d_inode->i_sem);
dput(root);
break;
default: return res;
}
return count;
}
static struct file_operations bm_entry_operations = {
read: bm_entry_read,
write: bm_entry_write,
};
/* /register */
static ssize_t bm_register_write(struct file *file, const char *buffer,
size_t count, loff_t *ppos)
{
Node *e;
struct dentry *root, *dentry;
struct super_block *sb = file->f_vfsmnt->mnt_sb;
int err = 0;
e = create_entry(buffer, count);
if (IS_ERR(e))
return PTR_ERR(e);
root = dget(sb->s_root);
down(&root->d_inode->i_sem);
dentry = lookup_one_len(e->name, root, strlen(e->name));
err = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
down(&root->d_inode->i_zombie);
if (dentry->d_inode) {
err = -EEXIST;
} else {
struct inode * inode = bm_get_inode(sb, S_IFREG | 0644);
err = -ENOMEM;
if (inode) {
write_lock(&entries_lock);
e->dentry = dget(dentry);
inode->u.generic_ip = e;
inode->i_fop = &bm_entry_operations;
d_instantiate(dentry, inode);
list_add(&e->list, &entries);
write_unlock(&entries_lock);
err = 0;
}
}
up(&root->d_inode->i_zombie);
dput(dentry);
}
up(&root->d_inode->i_sem);
dput(root);
if (err) {
kfree(e);
return -EINVAL;
}
return count;
}
static struct file_operations bm_register_operations = {
write: bm_register_write,
};
/* /status */
static ssize_t
bm_status_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos)
{
char *s = enabled ? "enabled" : "disabled";
int len = strlen(s);
loff_t pos = *ppos;
if (pos < 0)
return -EINVAL;
if (pos >= len)
return 0;
if (len < pos + nbytes)
nbytes = len - pos;
if (copy_to_user(buf, s + pos, nbytes))
return -EFAULT;
*ppos = pos + nbytes;
return nbytes;
}
static ssize_t bm_status_write(struct file * file, const char * buffer,
size_t count, loff_t *ppos)
{
int res = parse_command(buffer, count);
struct dentry *root;
switch (res) {
case 1: enabled = 0; break;
case 2: enabled = 1; break;
case 3: root = dget(file->f_vfsmnt->mnt_sb->s_root);
down(&root->d_inode->i_sem);
down(&root->d_inode->i_zombie);
while (!list_empty(&entries))
kill_node(list_entry(entries.next, Node, list));
up(&root->d_inode->i_zombie);
up(&root->d_inode->i_sem);
dput(root);
default: return res;
}
return count;
}
static struct file_operations bm_status_operations = {
read: bm_status_read,
write: bm_status_write,
};
/* / */
static struct dentry * bm_lookup(struct inode *dir, struct dentry *dentry)
{
d_add(dentry, NULL);
return NULL;
}
static struct file_operations bm_dir_operations = {
read: generic_read_dir,
readdir: dcache_readdir,
};
static struct inode_operations bm_dir_inode_operations = {
lookup: bm_lookup,
};
/* Superblock handling */
static int bm_statfs(struct super_block *sb, struct statfs *buf)
{
buf->f_type = sb->s_magic;
buf->f_bsize = PAGE_CACHE_SIZE;
buf->f_namelen = 255;
return 0;
}
static struct super_operations s_ops = {
statfs: bm_statfs,
put_inode: force_delete,
clear_inode: bm_clear_inode,
};
static struct super_block *bm_read_super(struct super_block * sb, void * data, int silent)
{
struct qstr names[2] = {{name:"status"}, {name:"register"}};
struct inode * inode;
struct dentry * dentry[3];
int i;
for (i=0; i<sizeof(names)/sizeof(names[0]); i++) {
names[i].len = strlen(names[i].name);
names[i].hash = full_name_hash(names[i].name, names[i].len);
}
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = 0x42494e4d;
sb->s_op = &s_ops;
inode = bm_get_inode(sb, S_IFDIR | 0755);
if (!inode)
return NULL;
inode->i_op = &bm_dir_inode_operations;
inode->i_fop = &bm_dir_operations;
dentry[0] = d_alloc_root(inode);
if (!dentry[0]) {
iput(inode);
return NULL;
}
dentry[1] = d_alloc(dentry[0], &names[0]);
if (!dentry[1])
goto out1;
dentry[2] = d_alloc(dentry[0], &names[1]);
if (!dentry[2])
goto out2;
inode = bm_get_inode(sb, S_IFREG | 0644);
if (!inode)
goto out3;
inode->i_fop = &bm_status_operations;
d_add(dentry[1], inode);
inode = bm_get_inode(sb, S_IFREG | 0400);
if (!inode)
goto out3;
inode->i_fop = &bm_register_operations;
d_add(dentry[2], inode);
sb->s_root = dentry[0];
return sb;
out3:
dput(dentry[2]);
out2:
dput(dentry[1]);
out1:
dput(dentry[0]);
return NULL;
}
static struct linux_binfmt misc_format = {
NULL, THIS_MODULE, load_misc_binary, NULL, NULL, 0
};
static DECLARE_FSTYPE(bm_fs_type, "binfmt_misc", bm_read_super, FS_SINGLE|FS_LITTER);
static struct vfsmount *bm_mnt;
static int __init init_misc_binfmt(void)
{
int err = register_filesystem(&bm_fs_type);
if (!err) {
bm_mnt = kern_mount(&bm_fs_type);
err = PTR_ERR(bm_mnt);
if (IS_ERR(bm_mnt))
unregister_filesystem(&bm_fs_type);
else {
err = register_binfmt(&misc_format);
if (err) {
unregister_filesystem(&bm_fs_type);
kern_umount(bm_mnt);
}
}
}
return err;
}
static void __exit exit_misc_binfmt(void)
{
unregister_binfmt(&misc_format);
unregister_filesystem(&bm_fs_type);
kern_umount(bm_mnt);
}
EXPORT_NO_SYMBOLS;
module_init(init_misc_binfmt);
module_exit(exit_misc_binfmt);
MODULE_LICENSE("GPL");
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