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linux/fs/binfmt_misc.c
Christoph Hellwig 85fe4025c6 fs: do not assign default i_ino in new_inode 
Instead of always assigning an increasing inode number in new_inode
move the call to assign it into those callers that actually need it.
For now callers that need it is estimated conservatively, that is
the call is added to all filesystems that do not assign an i_ino
by themselves.  For a few more filesystems we can avoid assigning
any inode number given that they aren't user visible, and for others
it could be done lazily when an inode number is actually needed,
but that's left for later patches.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-25 21:26:11 -04:00

747 lines
15 KiB
C
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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/sched.h>
#include <linux/binfmts.h>
#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/syscalls.h>
#include <linux/fs.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};
#define MISC_FMT_PRESERVE_ARGV0 (1<<31)
#define MISC_FMT_OPEN_BINARY (1<<30)
#define MISC_FMT_CREDENTIALS (1<<29)
typedef struct {
struct list_head list;
unsigned long 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 DEFINE_RWLOCK(entries_lock);
static struct file_system_type bm_fs_type;
static struct vfsmount *bm_mnt;
static int entry_count;
/*
* 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->interp, '.');
struct list_head *l;
list_for_each(l, &entries) {
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 * interp_file = NULL;
char iname[BINPRM_BUF_SIZE];
const char *iname_addr = iname;
int retval;
int fd_binary = -1;
retval = -ENOEXEC;
if (!enabled)
goto _ret;
retval = -ENOEXEC;
if (bprm->recursion_depth > BINPRM_MAX_RECURSION)
goto _ret;
/* to keep locking time low, we copy the interpreter string */
read_lock(&entries_lock);
fmt = check_file(bprm);
if (fmt)
strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
read_unlock(&entries_lock);
if (!fmt)
goto _ret;
if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
retval = remove_arg_zero(bprm);
if (retval)
goto _ret;
}
if (fmt->flags & MISC_FMT_OPEN_BINARY) {
/* if the binary should be opened on behalf of the
* interpreter than keep it open and assign descriptor
* to it */
fd_binary = get_unused_fd();
if (fd_binary < 0) {
retval = fd_binary;
goto _ret;
}
fd_install(fd_binary, bprm->file);
/* if the binary is not readable than enforce mm->dumpable=0
regardless of the interpreter's permissions */
if (file_permission(bprm->file, MAY_READ))
bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
allow_write_access(bprm->file);
bprm->file = NULL;
/* mark the bprm that fd should be passed to interp */
bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
bprm->interp_data = fd_binary;
} else {
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
}
/* make argv[1] be the path to the binary */
retval = copy_strings_kernel (1, &bprm->interp, bprm);
if (retval < 0)
goto _error;
bprm->argc++;
/* add the interp as argv[0] */
retval = copy_strings_kernel (1, &iname_addr, bprm);
if (retval < 0)
goto _error;
bprm->argc ++;
bprm->interp = iname; /* for binfmt_script */
interp_file = open_exec (iname);
retval = PTR_ERR (interp_file);
if (IS_ERR (interp_file))
goto _error;
bprm->file = interp_file;
if (fmt->flags & MISC_FMT_CREDENTIALS) {
/*
* No need to call prepare_binprm(), it's already been
* done. bprm->buf is stale, update from interp_file.
*/
memset(bprm->buf, 0, BINPRM_BUF_SIZE);
retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
} else
retval = prepare_binprm (bprm);
if (retval < 0)
goto _error;
bprm->recursion_depth++;
retval = search_binary_handler (bprm, regs);
if (retval < 0)
goto _error;
_ret:
return retval;
_error:
if (fd_binary > 0)
sys_close(fd_binary);
bprm->interp_flags = 0;
bprm->interp_data = 0;
goto _ret;
}
/* 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;
}
static char * check_special_flags (char * sfs, Node * e)
{
char * p = sfs;
int cont = 1;
/* special flags */
while (cont) {
switch (*p) {
case 'P':
p++;
e->flags |= MISC_FMT_PRESERVE_ARGV0;
break;
case 'O':
p++;
e->flags |= MISC_FMT_OPEN_BINARY;
break;
case 'C':
p++;
/* this flags also implies the
open-binary flag */
e->flags |= (MISC_FMT_CREDENTIALS |
MISC_FMT_OPEN_BINARY);
break;
default:
cont = 0;
}
}
return p;
}
/*
* This registers a new binary format, it recognises the syntax
* ':name:type:offset:magic:mask:interpreter:flags'
* where the ':' is the IFS, that can be chosen with the first char
*/
static Node *create_entry(const char __user *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 = 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;
p = check_special_flags (p, e);
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 __user *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";
const char * flags = "flags: ";
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);
/* print the special flags */
sprintf (dp, "%s", flags);
dp += strlen (flags);
if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
*dp ++ = 'P';
}
if (e->flags & MISC_FMT_OPEN_BINARY) {
*dp ++ = 'O';
}
if (e->flags & MISC_FMT_CREDENTIALS) {
*dp ++ = 'C';
}
*dp ++ = '\n';
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_ino = get_next_ino();
inode->i_mode = mode;
inode->i_atime = inode->i_mtime = inode->i_ctime =
current_fs_time(inode->i_sb);
}
return inode;
}
static void bm_evict_inode(struct inode *inode)
{
end_writeback(inode);
kfree(inode->i_private);
}
static void kill_node(Node *e)
{
struct dentry *dentry;
write_lock(&entries_lock);
dentry = e->dentry;
if (dentry) {
list_del_init(&e->list);
e->dentry = NULL;
}
write_unlock(&entries_lock);
if (dentry) {
dentry->d_inode->i_nlink--;
d_drop(dentry);
dput(dentry);
simple_release_fs(&bm_mnt, &entry_count);
}
}
/* /<entry> */
static ssize_t
bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
{
Node *e = file->f_path.dentry->d_inode->i_private;
ssize_t res;
char *page;
if (!(page = (char*) __get_free_page(GFP_KERNEL)))
return -ENOMEM;
entry_status(e, page);
res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
free_page((unsigned long) page);
return res;
}
static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
struct dentry *root;
Node *e = file->f_path.dentry->d_inode->i_private;
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_path.mnt->mnt_sb->s_root);
mutex_lock(&root->d_inode->i_mutex);
kill_node(e);
mutex_unlock(&root->d_inode->i_mutex);
dput(root);
break;
default: return res;
}
return count;
}
static const struct file_operations bm_entry_operations = {
.read = bm_entry_read,
.write = bm_entry_write,
.llseek = default_llseek,
};
/* /register */
static ssize_t bm_register_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos)
{
Node *e;
struct inode *inode;
struct dentry *root, *dentry;
struct super_block *sb = file->f_path.mnt->mnt_sb;
int err = 0;
e = create_entry(buffer, count);
if (IS_ERR(e))
return PTR_ERR(e);
root = dget(sb->s_root);
mutex_lock(&root->d_inode->i_mutex);
dentry = lookup_one_len(e->name, root, strlen(e->name));
err = PTR_ERR(dentry);
if (IS_ERR(dentry))
goto out;
err = -EEXIST;
if (dentry->d_inode)
goto out2;
inode = bm_get_inode(sb, S_IFREG | 0644);
err = -ENOMEM;
if (!inode)
goto out2;
err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
if (err) {
iput(inode);
inode = NULL;
goto out2;
}
e->dentry = dget(dentry);
inode->i_private = e;
inode->i_fop = &bm_entry_operations;
d_instantiate(dentry, inode);
write_lock(&entries_lock);
list_add(&e->list, &entries);
write_unlock(&entries_lock);
err = 0;
out2:
dput(dentry);
out:
mutex_unlock(&root->d_inode->i_mutex);
dput(root);
if (err) {
kfree(e);
return -EINVAL;
}
return count;
}
static const struct file_operations bm_register_operations = {
.write = bm_register_write,
.llseek = noop_llseek,
};
/* /status */
static ssize_t
bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
char *s = enabled ? "enabled\n" : "disabled\n";
return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
}
static ssize_t bm_status_write(struct file * file, const char __user * 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_path.mnt->mnt_sb->s_root);
mutex_lock(&root->d_inode->i_mutex);
while (!list_empty(&entries))
kill_node(list_entry(entries.next, Node, list));
mutex_unlock(&root->d_inode->i_mutex);
dput(root);
default: return res;
}
return count;
}
static const struct file_operations bm_status_operations = {
.read = bm_status_read,
.write = bm_status_write,
.llseek = default_llseek,
};
/* Superblock handling */
static const struct super_operations s_ops = {
.statfs = simple_statfs,
.evict_inode = bm_evict_inode,
};
static int bm_fill_super(struct super_block * sb, void * data, int silent)
{
static struct tree_descr bm_files[] = {
[2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
[3] = {"register", &bm_register_operations, S_IWUSR},
/* last one */ {""}
};
int err = simple_fill_super(sb, 0x42494e4d, bm_files);
if (!err)
sb->s_op = &s_ops;
return err;
}
static int bm_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
return get_sb_single(fs_type, flags, data, bm_fill_super, mnt);
}
static struct linux_binfmt misc_format = {
.module = THIS_MODULE,
.load_binary = load_misc_binary,
};
static struct file_system_type bm_fs_type = {
.owner = THIS_MODULE,
.name = "binfmt_misc",
.get_sb = bm_get_sb,
.kill_sb = kill_litter_super,
};
static int __init init_misc_binfmt(void)
{
int err = register_filesystem(&bm_fs_type);
if (!err) {
err = insert_binfmt(&misc_format);
if (err)
unregister_filesystem(&bm_fs_type);
}
return err;
}
static void __exit exit_misc_binfmt(void)
{
unregister_binfmt(&misc_format);
unregister_filesystem(&bm_fs_type);
}
core_initcall(init_misc_binfmt);
module_exit(exit_misc_binfmt);
MODULE_LICENSE("GPL");
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