4 * Copyright (C) 1997 Richard Günther
6 * binfmt_misc detects binaries via a magic or filename extension and invokes
7 * a specified wrapper. See Documentation/binfmt_misc.txt for more details.
10 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/magic.h>
16 #include <linux/binfmts.h>
17 #include <linux/slab.h>
18 #include <linux/ctype.h>
19 #include <linux/string_helpers.h>
20 #include <linux/file.h>
21 #include <linux/pagemap.h>
22 #include <linux/namei.h>
23 #include <linux/mount.h>
24 #include <linux/syscalls.h>
26 #include <linux/uaccess.h>
35 VERBOSE_STATUS
= 1 /* make it zero to save 400 bytes kernel memory */
38 static LIST_HEAD(entries
);
39 static int enabled
= 1;
41 enum {Enabled
, Magic
};
42 #define MISC_FMT_PRESERVE_ARGV0 (1 << 31)
43 #define MISC_FMT_OPEN_BINARY (1 << 30)
44 #define MISC_FMT_CREDENTIALS (1 << 29)
47 struct list_head list
;
48 unsigned long flags
; /* type, status, etc. */
49 int offset
; /* offset of magic */
50 int size
; /* size of magic/mask */
51 char *magic
; /* magic or filename extension */
52 char *mask
; /* mask, NULL for exact match */
53 char *interpreter
; /* filename of interpreter */
55 struct dentry
*dentry
;
58 static DEFINE_RWLOCK(entries_lock
);
59 static struct file_system_type bm_fs_type
;
60 static struct vfsmount
*bm_mnt
;
61 static int entry_count
;
64 * Max length of the register string. Determined by:
68 * - offset: 3 bytes (has to be smaller than BINPRM_BUF_SIZE)
69 * - magic: 128 bytes (512 in escaped form)
70 * - mask: 128 bytes (512 in escaped form)
73 * Round that up a bit, and then back off to hold the internal data
76 #define MAX_REGISTER_LENGTH 1920
79 * Check if we support the binfmt
80 * if we do, return the node, else NULL
81 * locking is done in load_misc_binary
83 static Node
*check_file(struct linux_binprm
*bprm
)
85 char *p
= strrchr(bprm
->interp
, '.');
88 /* Walk all the registered handlers. */
89 list_for_each(l
, &entries
) {
90 Node
*e
= list_entry(l
, Node
, list
);
94 /* Make sure this one is currently enabled. */
95 if (!test_bit(Enabled
, &e
->flags
))
98 /* Do matching based on extension if applicable. */
99 if (!test_bit(Magic
, &e
->flags
)) {
100 if (p
&& !strcmp(e
->magic
, p
+ 1))
105 /* Do matching based on magic & mask. */
106 s
= bprm
->buf
+ e
->offset
;
108 for (j
= 0; j
< e
->size
; j
++)
109 if ((*s
++ ^ e
->magic
[j
]) & e
->mask
[j
])
112 for (j
= 0; j
< e
->size
; j
++)
113 if ((*s
++ ^ e
->magic
[j
]))
125 static int load_misc_binary(struct linux_binprm
*bprm
)
128 struct file
*interp_file
= NULL
;
129 char iname
[BINPRM_BUF_SIZE
];
130 const char *iname_addr
= iname
;
138 /* to keep locking time low, we copy the interpreter string */
139 read_lock(&entries_lock
);
140 fmt
= check_file(bprm
);
142 strlcpy(iname
, fmt
->interpreter
, BINPRM_BUF_SIZE
);
143 read_unlock(&entries_lock
);
147 /* Need to be able to load the file after exec */
148 if (bprm
->interp_flags
& BINPRM_FLAGS_PATH_INACCESSIBLE
)
151 if (!(fmt
->flags
& MISC_FMT_PRESERVE_ARGV0
)) {
152 retval
= remove_arg_zero(bprm
);
157 if (fmt
->flags
& MISC_FMT_OPEN_BINARY
) {
159 /* if the binary should be opened on behalf of the
160 * interpreter than keep it open and assign descriptor
163 fd_binary
= get_unused_fd_flags(0);
168 fd_install(fd_binary
, bprm
->file
);
170 /* if the binary is not readable than enforce mm->dumpable=0
171 regardless of the interpreter's permissions */
172 would_dump(bprm
, bprm
->file
);
174 allow_write_access(bprm
->file
);
177 /* mark the bprm that fd should be passed to interp */
178 bprm
->interp_flags
|= BINPRM_FLAGS_EXECFD
;
179 bprm
->interp_data
= fd_binary
;
182 allow_write_access(bprm
->file
);
186 /* make argv[1] be the path to the binary */
187 retval
= copy_strings_kernel(1, &bprm
->interp
, bprm
);
192 /* add the interp as argv[0] */
193 retval
= copy_strings_kernel(1, &iname_addr
, bprm
);
198 /* Update interp in case binfmt_script needs it. */
199 retval
= bprm_change_interp(iname
, bprm
);
203 interp_file
= open_exec(iname
);
204 retval
= PTR_ERR(interp_file
);
205 if (IS_ERR(interp_file
))
208 bprm
->file
= interp_file
;
209 if (fmt
->flags
& MISC_FMT_CREDENTIALS
) {
211 * No need to call prepare_binprm(), it's already been
212 * done. bprm->buf is stale, update from interp_file.
214 memset(bprm
->buf
, 0, BINPRM_BUF_SIZE
);
215 retval
= kernel_read(bprm
->file
, 0, bprm
->buf
, BINPRM_BUF_SIZE
);
217 retval
= prepare_binprm(bprm
);
222 retval
= search_binary_handler(bprm
);
230 sys_close(fd_binary
);
231 bprm
->interp_flags
= 0;
232 bprm
->interp_data
= 0;
236 /* Command parsers */
239 * parses and copies one argument enclosed in del from *sp to *dp,
240 * recognising the \x special.
241 * returns pointer to the copied argument or NULL in case of an
242 * error (and sets err) or null argument length.
244 static char *scanarg(char *s
, char del
)
248 while ((c
= *s
++) != del
) {
249 if (c
== '\\' && *s
== 'x') {
260 static char *check_special_flags(char *sfs
, Node
*e
)
269 pr_debug("register: flag: P (preserve argv0)\n");
271 e
->flags
|= MISC_FMT_PRESERVE_ARGV0
;
274 pr_debug("register: flag: O (open binary)\n");
276 e
->flags
|= MISC_FMT_OPEN_BINARY
;
279 pr_debug("register: flag: C (preserve creds)\n");
281 /* this flags also implies the
283 e
->flags
|= (MISC_FMT_CREDENTIALS
|
284 MISC_FMT_OPEN_BINARY
);
295 * This registers a new binary format, it recognises the syntax
296 * ':name:type:offset:magic:mask:interpreter:flags'
297 * where the ':' is the IFS, that can be chosen with the first char
299 static Node
*create_entry(const char __user
*buffer
, size_t count
)
306 pr_debug("register: received %zu bytes\n", count
);
308 /* some sanity checks */
310 if ((count
< 11) || (count
> MAX_REGISTER_LENGTH
))
314 memsize
= sizeof(Node
) + count
+ 8;
315 e
= kmalloc(memsize
, GFP_KERNEL
);
319 p
= buf
= (char *)e
+ sizeof(Node
);
321 memset(e
, 0, sizeof(Node
));
322 if (copy_from_user(buf
, buffer
, count
))
325 del
= *p
++; /* delimeter */
327 pr_debug("register: delim: %#x {%c}\n", del
, del
);
329 /* Pad the buffer with the delim to simplify parsing below. */
330 memset(buf
+ count
, del
, 8);
332 /* Parse the 'name' field. */
339 !strcmp(e
->name
, ".") ||
340 !strcmp(e
->name
, "..") ||
341 strchr(e
->name
, '/'))
344 pr_debug("register: name: {%s}\n", e
->name
);
346 /* Parse the 'type' field. */
349 pr_debug("register: type: E (extension)\n");
350 e
->flags
= 1 << Enabled
;
353 pr_debug("register: type: M (magic)\n");
354 e
->flags
= (1 << Enabled
) | (1 << Magic
);
362 if (test_bit(Magic
, &e
->flags
)) {
363 /* Handle the 'M' (magic) format. */
366 /* Parse the 'offset' field. */
371 e
->offset
= simple_strtoul(p
, &p
, 10);
374 pr_debug("register: offset: %#x\n", e
->offset
);
376 /* Parse the 'magic' field. */
385 print_hex_dump_bytes(
386 KBUILD_MODNAME
": register: magic[raw]: ",
387 DUMP_PREFIX_NONE
, e
->magic
, p
- e
->magic
);
389 /* Parse the 'mask' field. */
397 pr_debug("register: mask[raw]: none\n");
398 } else if (USE_DEBUG
)
399 print_hex_dump_bytes(
400 KBUILD_MODNAME
": register: mask[raw]: ",
401 DUMP_PREFIX_NONE
, e
->mask
, p
- e
->mask
);
404 * Decode the magic & mask fields.
405 * Note: while we might have accepted embedded NUL bytes from
406 * above, the unescape helpers here will stop at the first one
409 e
->size
= string_unescape_inplace(e
->magic
, UNESCAPE_HEX
);
411 string_unescape_inplace(e
->mask
, UNESCAPE_HEX
) != e
->size
)
413 if (e
->size
+ e
->offset
> BINPRM_BUF_SIZE
)
415 pr_debug("register: magic/mask length: %i\n", e
->size
);
417 print_hex_dump_bytes(
418 KBUILD_MODNAME
": register: magic[decoded]: ",
419 DUMP_PREFIX_NONE
, e
->magic
, e
->size
);
423 char *masked
= kmalloc(e
->size
, GFP_KERNEL
);
425 print_hex_dump_bytes(
426 KBUILD_MODNAME
": register: mask[decoded]: ",
427 DUMP_PREFIX_NONE
, e
->mask
, e
->size
);
430 for (i
= 0; i
< e
->size
; ++i
)
431 masked
[i
] = e
->magic
[i
] & e
->mask
[i
];
432 print_hex_dump_bytes(
433 KBUILD_MODNAME
": register: magic[masked]: ",
434 DUMP_PREFIX_NONE
, masked
, e
->size
);
441 /* Handle the 'E' (extension) format. */
443 /* Skip the 'offset' field. */
449 /* Parse the 'magic' field. */
455 if (!e
->magic
[0] || strchr(e
->magic
, '/'))
457 pr_debug("register: extension: {%s}\n", e
->magic
);
459 /* Skip the 'mask' field. */
466 /* Parse the 'interpreter' field. */
472 if (!e
->interpreter
[0])
474 pr_debug("register: interpreter: {%s}\n", e
->interpreter
);
476 /* Parse the 'flags' field. */
477 p
= check_special_flags(p
, e
);
480 if (p
!= buf
+ count
)
490 return ERR_PTR(-EFAULT
);
493 return ERR_PTR(-EINVAL
);
497 * Set status of entry/binfmt_misc:
498 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
500 static int parse_command(const char __user
*buffer
, size_t count
)
506 if (copy_from_user(s
, buffer
, count
))
510 if (s
[count
- 1] == '\n')
512 if (count
== 1 && s
[0] == '0')
514 if (count
== 1 && s
[0] == '1')
516 if (count
== 2 && s
[0] == '-' && s
[1] == '1')
523 static void entry_status(Node
*e
, char *page
)
526 char *status
= "disabled";
527 const char *flags
= "flags: ";
529 if (test_bit(Enabled
, &e
->flags
))
532 if (!VERBOSE_STATUS
) {
533 sprintf(page
, "%s\n", status
);
537 sprintf(page
, "%s\ninterpreter %s\n", status
, e
->interpreter
);
538 dp
= page
+ strlen(page
);
540 /* print the special flags */
541 sprintf(dp
, "%s", flags
);
543 if (e
->flags
& MISC_FMT_PRESERVE_ARGV0
)
545 if (e
->flags
& MISC_FMT_OPEN_BINARY
)
547 if (e
->flags
& MISC_FMT_CREDENTIALS
)
551 if (!test_bit(Magic
, &e
->flags
)) {
552 sprintf(dp
, "extension .%s\n", e
->magic
);
556 sprintf(dp
, "offset %i\nmagic ", e
->offset
);
557 dp
= page
+ strlen(page
);
558 for (i
= 0; i
< e
->size
; i
++) {
559 sprintf(dp
, "%02x", 0xff & (int) (e
->magic
[i
]));
563 sprintf(dp
, "\nmask ");
565 for (i
= 0; i
< e
->size
; i
++) {
566 sprintf(dp
, "%02x", 0xff & (int) (e
->mask
[i
]));
575 static struct inode
*bm_get_inode(struct super_block
*sb
, int mode
)
577 struct inode
*inode
= new_inode(sb
);
580 inode
->i_ino
= get_next_ino();
581 inode
->i_mode
= mode
;
582 inode
->i_atime
= inode
->i_mtime
= inode
->i_ctime
=
583 current_fs_time(inode
->i_sb
);
588 static void bm_evict_inode(struct inode
*inode
)
591 kfree(inode
->i_private
);
594 static void kill_node(Node
*e
)
596 struct dentry
*dentry
;
598 write_lock(&entries_lock
);
601 list_del_init(&e
->list
);
604 write_unlock(&entries_lock
);
607 drop_nlink(dentry
->d_inode
);
610 simple_release_fs(&bm_mnt
, &entry_count
);
617 bm_entry_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
619 Node
*e
= file_inode(file
)->i_private
;
623 page
= (char *) __get_free_page(GFP_KERNEL
);
627 entry_status(e
, page
);
629 res
= simple_read_from_buffer(buf
, nbytes
, ppos
, page
, strlen(page
));
631 free_page((unsigned long) page
);
635 static ssize_t
bm_entry_write(struct file
*file
, const char __user
*buffer
,
636 size_t count
, loff_t
*ppos
)
639 Node
*e
= file_inode(file
)->i_private
;
640 int res
= parse_command(buffer
, count
);
644 /* Disable this handler. */
645 clear_bit(Enabled
, &e
->flags
);
648 /* Enable this handler. */
649 set_bit(Enabled
, &e
->flags
);
652 /* Delete this handler. */
653 root
= dget(file
->f_path
.dentry
->d_sb
->s_root
);
654 mutex_lock(&root
->d_inode
->i_mutex
);
658 mutex_unlock(&root
->d_inode
->i_mutex
);
668 static const struct file_operations bm_entry_operations
= {
669 .read
= bm_entry_read
,
670 .write
= bm_entry_write
,
671 .llseek
= default_llseek
,
676 static ssize_t
bm_register_write(struct file
*file
, const char __user
*buffer
,
677 size_t count
, loff_t
*ppos
)
681 struct dentry
*root
, *dentry
;
682 struct super_block
*sb
= file
->f_path
.dentry
->d_sb
;
685 e
= create_entry(buffer
, count
);
690 root
= dget(sb
->s_root
);
691 mutex_lock(&root
->d_inode
->i_mutex
);
692 dentry
= lookup_one_len(e
->name
, root
, strlen(e
->name
));
693 err
= PTR_ERR(dentry
);
701 inode
= bm_get_inode(sb
, S_IFREG
| 0644);
707 err
= simple_pin_fs(&bm_fs_type
, &bm_mnt
, &entry_count
);
714 e
->dentry
= dget(dentry
);
715 inode
->i_private
= e
;
716 inode
->i_fop
= &bm_entry_operations
;
718 d_instantiate(dentry
, inode
);
719 write_lock(&entries_lock
);
720 list_add(&e
->list
, &entries
);
721 write_unlock(&entries_lock
);
727 mutex_unlock(&root
->d_inode
->i_mutex
);
737 static const struct file_operations bm_register_operations
= {
738 .write
= bm_register_write
,
739 .llseek
= noop_llseek
,
745 bm_status_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
747 char *s
= enabled
? "enabled\n" : "disabled\n";
749 return simple_read_from_buffer(buf
, nbytes
, ppos
, s
, strlen(s
));
752 static ssize_t
bm_status_write(struct file
*file
, const char __user
*buffer
,
753 size_t count
, loff_t
*ppos
)
755 int res
= parse_command(buffer
, count
);
760 /* Disable all handlers. */
764 /* Enable all handlers. */
768 /* Delete all handlers. */
769 root
= dget(file
->f_path
.dentry
->d_sb
->s_root
);
770 mutex_lock(&root
->d_inode
->i_mutex
);
772 while (!list_empty(&entries
))
773 kill_node(list_entry(entries
.next
, Node
, list
));
775 mutex_unlock(&root
->d_inode
->i_mutex
);
785 static const struct file_operations bm_status_operations
= {
786 .read
= bm_status_read
,
787 .write
= bm_status_write
,
788 .llseek
= default_llseek
,
791 /* Superblock handling */
793 static const struct super_operations s_ops
= {
794 .statfs
= simple_statfs
,
795 .evict_inode
= bm_evict_inode
,
798 static int bm_fill_super(struct super_block
*sb
, void *data
, int silent
)
801 static struct tree_descr bm_files
[] = {
802 [2] = {"status", &bm_status_operations
, S_IWUSR
|S_IRUGO
},
803 [3] = {"register", &bm_register_operations
, S_IWUSR
},
807 err
= simple_fill_super(sb
, BINFMTFS_MAGIC
, bm_files
);
813 static struct dentry
*bm_mount(struct file_system_type
*fs_type
,
814 int flags
, const char *dev_name
, void *data
)
816 return mount_single(fs_type
, flags
, data
, bm_fill_super
);
819 static struct linux_binfmt misc_format
= {
820 .module
= THIS_MODULE
,
821 .load_binary
= load_misc_binary
,
824 static struct file_system_type bm_fs_type
= {
825 .owner
= THIS_MODULE
,
826 .name
= "binfmt_misc",
828 .kill_sb
= kill_litter_super
,
830 MODULE_ALIAS_FS("binfmt_misc");
832 static int __init
init_misc_binfmt(void)
834 int err
= register_filesystem(&bm_fs_type
);
836 insert_binfmt(&misc_format
);
840 static void __exit
exit_misc_binfmt(void)
842 unregister_binfmt(&misc_format
);
843 unregister_filesystem(&bm_fs_type
);
846 core_initcall(init_misc_binfmt
);
847 module_exit(exit_misc_binfmt
);
848 MODULE_LICENSE("GPL");