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 if (!(fmt
->flags
& MISC_FMT_PRESERVE_ARGV0
)) {
148 retval
= remove_arg_zero(bprm
);
153 if (fmt
->flags
& MISC_FMT_OPEN_BINARY
) {
155 /* if the binary should be opened on behalf of the
156 * interpreter than keep it open and assign descriptor
159 fd_binary
= get_unused_fd_flags(0);
164 fd_install(fd_binary
, bprm
->file
);
166 /* if the binary is not readable than enforce mm->dumpable=0
167 regardless of the interpreter's permissions */
168 would_dump(bprm
, bprm
->file
);
170 allow_write_access(bprm
->file
);
173 /* mark the bprm that fd should be passed to interp */
174 bprm
->interp_flags
|= BINPRM_FLAGS_EXECFD
;
175 bprm
->interp_data
= fd_binary
;
178 allow_write_access(bprm
->file
);
182 /* make argv[1] be the path to the binary */
183 retval
= copy_strings_kernel(1, &bprm
->interp
, bprm
);
188 /* add the interp as argv[0] */
189 retval
= copy_strings_kernel(1, &iname_addr
, bprm
);
194 /* Update interp in case binfmt_script needs it. */
195 retval
= bprm_change_interp(iname
, bprm
);
199 interp_file
= open_exec(iname
);
200 retval
= PTR_ERR(interp_file
);
201 if (IS_ERR(interp_file
))
204 bprm
->file
= interp_file
;
205 if (fmt
->flags
& MISC_FMT_CREDENTIALS
) {
207 * No need to call prepare_binprm(), it's already been
208 * done. bprm->buf is stale, update from interp_file.
210 memset(bprm
->buf
, 0, BINPRM_BUF_SIZE
);
211 retval
= kernel_read(bprm
->file
, 0, bprm
->buf
, BINPRM_BUF_SIZE
);
213 retval
= prepare_binprm(bprm
);
218 retval
= search_binary_handler(bprm
);
226 sys_close(fd_binary
);
227 bprm
->interp_flags
= 0;
228 bprm
->interp_data
= 0;
232 /* Command parsers */
235 * parses and copies one argument enclosed in del from *sp to *dp,
236 * recognising the \x special.
237 * returns pointer to the copied argument or NULL in case of an
238 * error (and sets err) or null argument length.
240 static char *scanarg(char *s
, char del
)
244 while ((c
= *s
++) != del
) {
245 if (c
== '\\' && *s
== 'x') {
256 static char *check_special_flags(char *sfs
, Node
*e
)
265 pr_debug("register: flag: P (preserve argv0)\n");
267 e
->flags
|= MISC_FMT_PRESERVE_ARGV0
;
270 pr_debug("register: flag: O (open binary)\n");
272 e
->flags
|= MISC_FMT_OPEN_BINARY
;
275 pr_debug("register: flag: C (preserve creds)\n");
277 /* this flags also implies the
279 e
->flags
|= (MISC_FMT_CREDENTIALS
|
280 MISC_FMT_OPEN_BINARY
);
291 * This registers a new binary format, it recognises the syntax
292 * ':name:type:offset:magic:mask:interpreter:flags'
293 * where the ':' is the IFS, that can be chosen with the first char
295 static Node
*create_entry(const char __user
*buffer
, size_t count
)
302 pr_debug("register: received %zu bytes\n", count
);
304 /* some sanity checks */
306 if ((count
< 11) || (count
> MAX_REGISTER_LENGTH
))
310 memsize
= sizeof(Node
) + count
+ 8;
311 e
= kmalloc(memsize
, GFP_KERNEL
);
315 p
= buf
= (char *)e
+ sizeof(Node
);
317 memset(e
, 0, sizeof(Node
));
318 if (copy_from_user(buf
, buffer
, count
))
321 del
= *p
++; /* delimeter */
323 pr_debug("register: delim: %#x {%c}\n", del
, del
);
325 /* Pad the buffer with the delim to simplify parsing below. */
326 memset(buf
+ count
, del
, 8);
328 /* Parse the 'name' field. */
335 !strcmp(e
->name
, ".") ||
336 !strcmp(e
->name
, "..") ||
337 strchr(e
->name
, '/'))
340 pr_debug("register: name: {%s}\n", e
->name
);
342 /* Parse the 'type' field. */
345 pr_debug("register: type: E (extension)\n");
346 e
->flags
= 1 << Enabled
;
349 pr_debug("register: type: M (magic)\n");
350 e
->flags
= (1 << Enabled
) | (1 << Magic
);
358 if (test_bit(Magic
, &e
->flags
)) {
359 /* Handle the 'M' (magic) format. */
362 /* Parse the 'offset' field. */
367 e
->offset
= simple_strtoul(p
, &p
, 10);
370 pr_debug("register: offset: %#x\n", e
->offset
);
372 /* Parse the 'magic' field. */
381 print_hex_dump_bytes(
382 KBUILD_MODNAME
": register: magic[raw]: ",
383 DUMP_PREFIX_NONE
, e
->magic
, p
- e
->magic
);
385 /* Parse the 'mask' field. */
393 pr_debug("register: mask[raw]: none\n");
394 } else if (USE_DEBUG
)
395 print_hex_dump_bytes(
396 KBUILD_MODNAME
": register: mask[raw]: ",
397 DUMP_PREFIX_NONE
, e
->mask
, p
- e
->mask
);
400 * Decode the magic & mask fields.
401 * Note: while we might have accepted embedded NUL bytes from
402 * above, the unescape helpers here will stop at the first one
405 e
->size
= string_unescape_inplace(e
->magic
, UNESCAPE_HEX
);
407 string_unescape_inplace(e
->mask
, UNESCAPE_HEX
) != e
->size
)
409 if (e
->size
+ e
->offset
> BINPRM_BUF_SIZE
)
411 pr_debug("register: magic/mask length: %i\n", e
->size
);
413 print_hex_dump_bytes(
414 KBUILD_MODNAME
": register: magic[decoded]: ",
415 DUMP_PREFIX_NONE
, e
->magic
, e
->size
);
419 char *masked
= kmalloc(e
->size
, GFP_KERNEL
);
421 print_hex_dump_bytes(
422 KBUILD_MODNAME
": register: mask[decoded]: ",
423 DUMP_PREFIX_NONE
, e
->mask
, e
->size
);
426 for (i
= 0; i
< e
->size
; ++i
)
427 masked
[i
] = e
->magic
[i
] & e
->mask
[i
];
428 print_hex_dump_bytes(
429 KBUILD_MODNAME
": register: magic[masked]: ",
430 DUMP_PREFIX_NONE
, masked
, e
->size
);
437 /* Handle the 'E' (extension) format. */
439 /* Skip the 'offset' field. */
445 /* Parse the 'magic' field. */
451 if (!e
->magic
[0] || strchr(e
->magic
, '/'))
453 pr_debug("register: extension: {%s}\n", e
->magic
);
455 /* Skip the 'mask' field. */
462 /* Parse the 'interpreter' field. */
468 if (!e
->interpreter
[0])
470 pr_debug("register: interpreter: {%s}\n", e
->interpreter
);
472 /* Parse the 'flags' field. */
473 p
= check_special_flags(p
, e
);
476 if (p
!= buf
+ count
)
486 return ERR_PTR(-EFAULT
);
489 return ERR_PTR(-EINVAL
);
493 * Set status of entry/binfmt_misc:
494 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
496 static int parse_command(const char __user
*buffer
, size_t count
)
502 if (copy_from_user(s
, buffer
, count
))
506 if (s
[count
- 1] == '\n')
508 if (count
== 1 && s
[0] == '0')
510 if (count
== 1 && s
[0] == '1')
512 if (count
== 2 && s
[0] == '-' && s
[1] == '1')
519 static void entry_status(Node
*e
, char *page
)
522 char *status
= "disabled";
523 const char *flags
= "flags: ";
525 if (test_bit(Enabled
, &e
->flags
))
528 if (!VERBOSE_STATUS
) {
529 sprintf(page
, "%s\n", status
);
533 sprintf(page
, "%s\ninterpreter %s\n", status
, e
->interpreter
);
534 dp
= page
+ strlen(page
);
536 /* print the special flags */
537 sprintf(dp
, "%s", flags
);
539 if (e
->flags
& MISC_FMT_PRESERVE_ARGV0
)
541 if (e
->flags
& MISC_FMT_OPEN_BINARY
)
543 if (e
->flags
& MISC_FMT_CREDENTIALS
)
547 if (!test_bit(Magic
, &e
->flags
)) {
548 sprintf(dp
, "extension .%s\n", e
->magic
);
552 sprintf(dp
, "offset %i\nmagic ", e
->offset
);
553 dp
= page
+ strlen(page
);
554 for (i
= 0; i
< e
->size
; i
++) {
555 sprintf(dp
, "%02x", 0xff & (int) (e
->magic
[i
]));
559 sprintf(dp
, "\nmask ");
561 for (i
= 0; i
< e
->size
; i
++) {
562 sprintf(dp
, "%02x", 0xff & (int) (e
->mask
[i
]));
571 static struct inode
*bm_get_inode(struct super_block
*sb
, int mode
)
573 struct inode
*inode
= new_inode(sb
);
576 inode
->i_ino
= get_next_ino();
577 inode
->i_mode
= mode
;
578 inode
->i_atime
= inode
->i_mtime
= inode
->i_ctime
=
579 current_fs_time(inode
->i_sb
);
584 static void bm_evict_inode(struct inode
*inode
)
587 kfree(inode
->i_private
);
590 static void kill_node(Node
*e
)
592 struct dentry
*dentry
;
594 write_lock(&entries_lock
);
597 list_del_init(&e
->list
);
600 write_unlock(&entries_lock
);
603 drop_nlink(dentry
->d_inode
);
606 simple_release_fs(&bm_mnt
, &entry_count
);
613 bm_entry_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
615 Node
*e
= file_inode(file
)->i_private
;
619 page
= (char *) __get_free_page(GFP_KERNEL
);
623 entry_status(e
, page
);
625 res
= simple_read_from_buffer(buf
, nbytes
, ppos
, page
, strlen(page
));
627 free_page((unsigned long) page
);
631 static ssize_t
bm_entry_write(struct file
*file
, const char __user
*buffer
,
632 size_t count
, loff_t
*ppos
)
635 Node
*e
= file_inode(file
)->i_private
;
636 int res
= parse_command(buffer
, count
);
640 /* Disable this handler. */
641 clear_bit(Enabled
, &e
->flags
);
644 /* Enable this handler. */
645 set_bit(Enabled
, &e
->flags
);
648 /* Delete this handler. */
649 root
= dget(file
->f_path
.dentry
->d_sb
->s_root
);
650 mutex_lock(&root
->d_inode
->i_mutex
);
654 mutex_unlock(&root
->d_inode
->i_mutex
);
664 static const struct file_operations bm_entry_operations
= {
665 .read
= bm_entry_read
,
666 .write
= bm_entry_write
,
667 .llseek
= default_llseek
,
672 static ssize_t
bm_register_write(struct file
*file
, const char __user
*buffer
,
673 size_t count
, loff_t
*ppos
)
677 struct dentry
*root
, *dentry
;
678 struct super_block
*sb
= file
->f_path
.dentry
->d_sb
;
681 e
= create_entry(buffer
, count
);
686 root
= dget(sb
->s_root
);
687 mutex_lock(&root
->d_inode
->i_mutex
);
688 dentry
= lookup_one_len(e
->name
, root
, strlen(e
->name
));
689 err
= PTR_ERR(dentry
);
697 inode
= bm_get_inode(sb
, S_IFREG
| 0644);
703 err
= simple_pin_fs(&bm_fs_type
, &bm_mnt
, &entry_count
);
710 e
->dentry
= dget(dentry
);
711 inode
->i_private
= e
;
712 inode
->i_fop
= &bm_entry_operations
;
714 d_instantiate(dentry
, inode
);
715 write_lock(&entries_lock
);
716 list_add(&e
->list
, &entries
);
717 write_unlock(&entries_lock
);
723 mutex_unlock(&root
->d_inode
->i_mutex
);
733 static const struct file_operations bm_register_operations
= {
734 .write
= bm_register_write
,
735 .llseek
= noop_llseek
,
741 bm_status_read(struct file
*file
, char __user
*buf
, size_t nbytes
, loff_t
*ppos
)
743 char *s
= enabled
? "enabled\n" : "disabled\n";
745 return simple_read_from_buffer(buf
, nbytes
, ppos
, s
, strlen(s
));
748 static ssize_t
bm_status_write(struct file
*file
, const char __user
*buffer
,
749 size_t count
, loff_t
*ppos
)
751 int res
= parse_command(buffer
, count
);
756 /* Disable all handlers. */
760 /* Enable all handlers. */
764 /* Delete all handlers. */
765 root
= dget(file
->f_path
.dentry
->d_sb
->s_root
);
766 mutex_lock(&root
->d_inode
->i_mutex
);
768 while (!list_empty(&entries
))
769 kill_node(list_entry(entries
.next
, Node
, list
));
771 mutex_unlock(&root
->d_inode
->i_mutex
);
781 static const struct file_operations bm_status_operations
= {
782 .read
= bm_status_read
,
783 .write
= bm_status_write
,
784 .llseek
= default_llseek
,
787 /* Superblock handling */
789 static const struct super_operations s_ops
= {
790 .statfs
= simple_statfs
,
791 .evict_inode
= bm_evict_inode
,
794 static int bm_fill_super(struct super_block
*sb
, void *data
, int silent
)
797 static struct tree_descr bm_files
[] = {
798 [2] = {"status", &bm_status_operations
, S_IWUSR
|S_IRUGO
},
799 [3] = {"register", &bm_register_operations
, S_IWUSR
},
803 err
= simple_fill_super(sb
, BINFMTFS_MAGIC
, bm_files
);
809 static struct dentry
*bm_mount(struct file_system_type
*fs_type
,
810 int flags
, const char *dev_name
, void *data
)
812 return mount_single(fs_type
, flags
, data
, bm_fill_super
);
815 static struct linux_binfmt misc_format
= {
816 .module
= THIS_MODULE
,
817 .load_binary
= load_misc_binary
,
820 static struct file_system_type bm_fs_type
= {
821 .owner
= THIS_MODULE
,
822 .name
= "binfmt_misc",
824 .kill_sb
= kill_litter_super
,
826 MODULE_ALIAS_FS("binfmt_misc");
828 static int __init
init_misc_binfmt(void)
830 int err
= register_filesystem(&bm_fs_type
);
832 insert_binfmt(&misc_format
);
836 static void __exit
exit_misc_binfmt(void)
838 unregister_binfmt(&misc_format
);
839 unregister_filesystem(&bm_fs_type
);
842 core_initcall(init_misc_binfmt
);
843 module_exit(exit_misc_binfmt
);
844 MODULE_LICENSE("GPL");