1/*
2 *  binfmt_misc.c
3 *
4 *  Copyright (C) 1997 Richard G��nther
5 *
6 *  binfmt_misc detects binaries via a magic or filename extension and invokes
7 *  a specified wrapper. This should obsolete binfmt_java, binfmt_em86 and
8 *  binfmt_mz.
9 *
10 *  1997-04-25 first version
11 *  [...]
12 *  1997-05-19 cleanup
13 *  1997-06-26 hpa: pass the real filename rather than argv[0]
14 *  1997-06-30 minor cleanup
15 *  1997-08-09 removed extension stripping, locking cleanup
16 *  2001-02-28 AV: rewritten into something that resembles C. Original didn't.
17 */
18
19#include <linux/module.h>
20#include <linux/init.h>
21#include <linux/sched.h>
22#include <linux/binfmts.h>
23#include <linux/slab.h>
24#include <linux/ctype.h>
25#include <linux/file.h>
26#include <linux/pagemap.h>
27#include <linux/namei.h>
28#include <linux/mount.h>
29#include <linux/syscalls.h>
30#include <linux/fs.h>
31
32#include <asm/uaccess.h>
33
34enum {
35	VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
36};
37
38static LIST_HEAD(entries);
39static int enabled = 1;
40
41enum {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)
45
46typedef struct {
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 */
54	char *name;
55	struct dentry *dentry;
56} Node;
57
58static DEFINE_RWLOCK(entries_lock);
59static struct file_system_type bm_fs_type;
60static struct vfsmount *bm_mnt;
61static int entry_count;
62
63/*
64 * Check if we support the binfmt
65 * if we do, return the node, else NULL
66 * locking is done in load_misc_binary
67 */
68static Node *check_file(struct linux_binprm *bprm)
69{
70	char *p = strrchr(bprm->interp, '.');
71	struct list_head *l;
72
73	list_for_each(l, &entries) {
74		Node *e = list_entry(l, Node, list);
75		char *s;
76		int j;
77
78		if (!test_bit(Enabled, &e->flags))
79			continue;
80
81		if (!test_bit(Magic, &e->flags)) {
82			if (p && !strcmp(e->magic, p + 1))
83				return e;
84			continue;
85		}
86
87		s = bprm->buf + e->offset;
88		if (e->mask) {
89			for (j = 0; j < e->size; j++)
90				if ((*s++ ^ e->magic[j]) & e->mask[j])
91					break;
92		} else {
93			for (j = 0; j < e->size; j++)
94				if ((*s++ ^ e->magic[j]))
95					break;
96		}
97		if (j == e->size)
98			return e;
99	}
100	return NULL;
101}
102
103/*
104 * the loader itself
105 */
106static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
107{
108	Node *fmt;
109	struct file * interp_file = NULL;
110	char iname[BINPRM_BUF_SIZE];
111	const char *iname_addr = iname;
112	int retval;
113	int fd_binary = -1;
114
115	retval = -ENOEXEC;
116	if (!enabled)
117		goto _ret;
118
119	retval = -ENOEXEC;
120	if (bprm->recursion_depth > BINPRM_MAX_RECURSION)
121		goto _ret;
122
123	/* to keep locking time low, we copy the interpreter string */
124	read_lock(&entries_lock);
125	fmt = check_file(bprm);
126	if (fmt)
127		strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
128	read_unlock(&entries_lock);
129	if (!fmt)
130		goto _ret;
131
132	if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
133		retval = remove_arg_zero(bprm);
134		if (retval)
135			goto _ret;
136	}
137
138	if (fmt->flags & MISC_FMT_OPEN_BINARY) {
139
140		/* if the binary should be opened on behalf of the
141		 * interpreter than keep it open and assign descriptor
142		 * to it */
143 		fd_binary = get_unused_fd();
144 		if (fd_binary < 0) {
145 			retval = fd_binary;
146 			goto _ret;
147 		}
148 		fd_install(fd_binary, bprm->file);
149
150		/* if the binary is not readable than enforce mm->dumpable=0
151		   regardless of the interpreter's permissions */
152		if (file_permission(bprm->file, MAY_READ))
153			bprm->interp_flags |= BINPRM_FLAGS_ENFORCE_NONDUMP;
154
155		allow_write_access(bprm->file);
156		bprm->file = NULL;
157
158		/* mark the bprm that fd should be passed to interp */
159		bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
160		bprm->interp_data = fd_binary;
161
162 	} else {
163 		allow_write_access(bprm->file);
164 		fput(bprm->file);
165 		bprm->file = NULL;
166 	}
167	/* make argv[1] be the path to the binary */
168	retval = copy_strings_kernel (1, &bprm->interp, bprm);
169	if (retval < 0)
170		goto _error;
171	bprm->argc++;
172
173	/* add the interp as argv[0] */
174	retval = copy_strings_kernel (1, &iname_addr, bprm);
175	if (retval < 0)
176		goto _error;
177	bprm->argc ++;
178
179	bprm->interp = iname;	/* for binfmt_script */
180
181	interp_file = open_exec (iname);
182	retval = PTR_ERR (interp_file);
183	if (IS_ERR (interp_file))
184		goto _error;
185
186	bprm->file = interp_file;
187	if (fmt->flags & MISC_FMT_CREDENTIALS) {
188		/*
189		 * No need to call prepare_binprm(), it's already been
190		 * done.  bprm->buf is stale, update from interp_file.
191		 */
192		memset(bprm->buf, 0, BINPRM_BUF_SIZE);
193		retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
194	} else
195		retval = prepare_binprm (bprm);
196
197	if (retval < 0)
198		goto _error;
199
200	bprm->recursion_depth++;
201
202	retval = search_binary_handler (bprm, regs);
203	if (retval < 0)
204		goto _error;
205
206_ret:
207	return retval;
208_error:
209	if (fd_binary > 0)
210		sys_close(fd_binary);
211	bprm->interp_flags = 0;
212	bprm->interp_data = 0;
213	goto _ret;
214}
215
216/* Command parsers */
217
218/*
219 * parses and copies one argument enclosed in del from *sp to *dp,
220 * recognising the \x special.
221 * returns pointer to the copied argument or NULL in case of an
222 * error (and sets err) or null argument length.
223 */
224static char *scanarg(char *s, char del)
225{
226	char c;
227
228	while ((c = *s++) != del) {
229		if (c == '\\' && *s == 'x') {
230			s++;
231			if (!isxdigit(*s++))
232				return NULL;
233			if (!isxdigit(*s++))
234				return NULL;
235		}
236	}
237	return s;
238}
239
240static int unquote(char *from)
241{
242	char c = 0, *s = from, *p = from;
243
244	while ((c = *s++) != '\0') {
245		if (c == '\\' && *s == 'x') {
246			s++;
247			c = toupper(*s++);
248			*p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
249			c = toupper(*s++);
250			*p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
251			continue;
252		}
253		*p++ = c;
254	}
255	return p - from;
256}
257
258static char * check_special_flags (char * sfs, Node * e)
259{
260	char * p = sfs;
261	int cont = 1;
262
263	/* special flags */
264	while (cont) {
265		switch (*p) {
266			case 'P':
267				p++;
268				e->flags |= MISC_FMT_PRESERVE_ARGV0;
269				break;
270			case 'O':
271				p++;
272				e->flags |= MISC_FMT_OPEN_BINARY;
273				break;
274			case 'C':
275				p++;
276				/* this flags also implies the
277				   open-binary flag */
278				e->flags |= (MISC_FMT_CREDENTIALS |
279						MISC_FMT_OPEN_BINARY);
280				break;
281			default:
282				cont = 0;
283		}
284	}
285
286	return p;
287}
288/*
289 * This registers a new binary format, it recognises the syntax
290 * ':name:type:offset:magic:mask:interpreter:flags'
291 * where the ':' is the IFS, that can be chosen with the first char
292 */
293static Node *create_entry(const char __user *buffer, size_t count)
294{
295	Node *e;
296	int memsize, err;
297	char *buf, *p;
298	char del;
299
300	/* some sanity checks */
301	err = -EINVAL;
302	if ((count < 11) || (count > 256))
303		goto out;
304
305	err = -ENOMEM;
306	memsize = sizeof(Node) + count + 8;
307	e = kmalloc(memsize, GFP_USER);
308	if (!e)
309		goto out;
310
311	p = buf = (char *)e + sizeof(Node);
312
313	memset(e, 0, sizeof(Node));
314	if (copy_from_user(buf, buffer, count))
315		goto Efault;
316
317	del = *p++;	/* delimeter */
318
319	memset(buf+count, del, 8);
320
321	e->name = p;
322	p = strchr(p, del);
323	if (!p)
324		goto Einval;
325	*p++ = '\0';
326	if (!e->name[0] ||
327	    !strcmp(e->name, ".") ||
328	    !strcmp(e->name, "..") ||
329	    strchr(e->name, '/'))
330		goto Einval;
331	switch (*p++) {
332		case 'E': e->flags = 1<<Enabled; break;
333		case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
334		default: goto Einval;
335	}
336	if (*p++ != del)
337		goto Einval;
338	if (test_bit(Magic, &e->flags)) {
339		char *s = strchr(p, del);
340		if (!s)
341			goto Einval;
342		*s++ = '\0';
343		e->offset = simple_strtoul(p, &p, 10);
344		if (*p++)
345			goto Einval;
346		e->magic = p;
347		p = scanarg(p, del);
348		if (!p)
349			goto Einval;
350		p[-1] = '\0';
351		if (!e->magic[0])
352			goto Einval;
353		e->mask = p;
354		p = scanarg(p, del);
355		if (!p)
356			goto Einval;
357		p[-1] = '\0';
358		if (!e->mask[0])
359			e->mask = NULL;
360		e->size = unquote(e->magic);
361		if (e->mask && unquote(e->mask) != e->size)
362			goto Einval;
363		if (e->size + e->offset > BINPRM_BUF_SIZE)
364			goto Einval;
365	} else {
366		p = strchr(p, del);
367		if (!p)
368			goto Einval;
369		*p++ = '\0';
370		e->magic = p;
371		p = strchr(p, del);
372		if (!p)
373			goto Einval;
374		*p++ = '\0';
375		if (!e->magic[0] || strchr(e->magic, '/'))
376			goto Einval;
377		p = strchr(p, del);
378		if (!p)
379			goto Einval;
380		*p++ = '\0';
381	}
382	e->interpreter = p;
383	p = strchr(p, del);
384	if (!p)
385		goto Einval;
386	*p++ = '\0';
387	if (!e->interpreter[0])
388		goto Einval;
389
390
391	p = check_special_flags (p, e);
392
393	if (*p == '\n')
394		p++;
395	if (p != buf + count)
396		goto Einval;
397	return e;
398
399out:
400	return ERR_PTR(err);
401
402Efault:
403	kfree(e);
404	return ERR_PTR(-EFAULT);
405Einval:
406	kfree(e);
407	return ERR_PTR(-EINVAL);
408}
409
410/*
411 * Set status of entry/binfmt_misc:
412 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
413 */
414static int parse_command(const char __user *buffer, size_t count)
415{
416	char s[4];
417
418	if (!count)
419		return 0;
420	if (count > 3)
421		return -EINVAL;
422	if (copy_from_user(s, buffer, count))
423		return -EFAULT;
424	if (s[count-1] == '\n')
425		count--;
426	if (count == 1 && s[0] == '0')
427		return 1;
428	if (count == 1 && s[0] == '1')
429		return 2;
430	if (count == 2 && s[0] == '-' && s[1] == '1')
431		return 3;
432	return -EINVAL;
433}
434
435/* generic stuff */
436
437static void entry_status(Node *e, char *page)
438{
439	char *dp;
440	char *status = "disabled";
441	const char * flags = "flags: ";
442
443	if (test_bit(Enabled, &e->flags))
444		status = "enabled";
445
446	if (!VERBOSE_STATUS) {
447		sprintf(page, "%s\n", status);
448		return;
449	}
450
451	sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
452	dp = page + strlen(page);
453
454	/* print the special flags */
455	sprintf (dp, "%s", flags);
456	dp += strlen (flags);
457	if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
458		*dp ++ = 'P';
459	}
460	if (e->flags & MISC_FMT_OPEN_BINARY) {
461		*dp ++ = 'O';
462	}
463	if (e->flags & MISC_FMT_CREDENTIALS) {
464		*dp ++ = 'C';
465	}
466	*dp ++ = '\n';
467
468
469	if (!test_bit(Magic, &e->flags)) {
470		sprintf(dp, "extension .%s\n", e->magic);
471	} else {
472		int i;
473
474		sprintf(dp, "offset %i\nmagic ", e->offset);
475		dp = page + strlen(page);
476		for (i = 0; i < e->size; i++) {
477			sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
478			dp += 2;
479		}
480		if (e->mask) {
481			sprintf(dp, "\nmask ");
482			dp += 6;
483			for (i = 0; i < e->size; i++) {
484				sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
485				dp += 2;
486			}
487		}
488		*dp++ = '\n';
489		*dp = '\0';
490	}
491}
492
493static struct inode *bm_get_inode(struct super_block *sb, int mode)
494{
495	struct inode * inode = new_inode(sb);
496
497	if (inode) {
498		inode->i_mode = mode;
499		inode->i_atime = inode->i_mtime = inode->i_ctime =
500			current_fs_time(inode->i_sb);
501	}
502	return inode;
503}
504
505static void bm_evict_inode(struct inode *inode)
506{
507	end_writeback(inode);
508	kfree(inode->i_private);
509}
510
511static void kill_node(Node *e)
512{
513	struct dentry *dentry;
514
515	write_lock(&entries_lock);
516	dentry = e->dentry;
517	if (dentry) {
518		list_del_init(&e->list);
519		e->dentry = NULL;
520	}
521	write_unlock(&entries_lock);
522
523	if (dentry) {
524		dentry->d_inode->i_nlink--;
525		d_drop(dentry);
526		dput(dentry);
527		simple_release_fs(&bm_mnt, &entry_count);
528	}
529}
530
531/* /<entry> */
532
533static ssize_t
534bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
535{
536	Node *e = file->f_path.dentry->d_inode->i_private;
537	ssize_t res;
538	char *page;
539
540	if (!(page = (char*) __get_free_page(GFP_KERNEL)))
541		return -ENOMEM;
542
543	entry_status(e, page);
544
545	res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
546
547	free_page((unsigned long) page);
548	return res;
549}
550
551static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
552				size_t count, loff_t *ppos)
553{
554	struct dentry *root;
555	Node *e = file->f_path.dentry->d_inode->i_private;
556	int res = parse_command(buffer, count);
557
558	switch (res) {
559		case 1: clear_bit(Enabled, &e->flags);
560			break;
561		case 2: set_bit(Enabled, &e->flags);
562			break;
563		case 3: root = dget(file->f_path.mnt->mnt_sb->s_root);
564			mutex_lock(&root->d_inode->i_mutex);
565
566			kill_node(e);
567
568			mutex_unlock(&root->d_inode->i_mutex);
569			dput(root);
570			break;
571		default: return res;
572	}
573	return count;
574}
575
576static const struct file_operations bm_entry_operations = {
577	.read		= bm_entry_read,
578	.write		= bm_entry_write,
579};
580
581/* /register */
582
583static ssize_t bm_register_write(struct file *file, const char __user *buffer,
584			       size_t count, loff_t *ppos)
585{
586	Node *e;
587	struct inode *inode;
588	struct dentry *root, *dentry;
589	struct super_block *sb = file->f_path.mnt->mnt_sb;
590	int err = 0;
591
592	e = create_entry(buffer, count);
593
594	if (IS_ERR(e))
595		return PTR_ERR(e);
596
597	root = dget(sb->s_root);
598	mutex_lock(&root->d_inode->i_mutex);
599	dentry = lookup_one_len(e->name, root, strlen(e->name));
600	err = PTR_ERR(dentry);
601	if (IS_ERR(dentry))
602		goto out;
603
604	err = -EEXIST;
605	if (dentry->d_inode)
606		goto out2;
607
608	inode = bm_get_inode(sb, S_IFREG | 0644);
609
610	err = -ENOMEM;
611	if (!inode)
612		goto out2;
613
614	err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
615	if (err) {
616		iput(inode);
617		inode = NULL;
618		goto out2;
619	}
620
621	e->dentry = dget(dentry);
622	inode->i_private = e;
623	inode->i_fop = &bm_entry_operations;
624
625	d_instantiate(dentry, inode);
626	write_lock(&entries_lock);
627	list_add(&e->list, &entries);
628	write_unlock(&entries_lock);
629
630	err = 0;
631out2:
632	dput(dentry);
633out:
634	mutex_unlock(&root->d_inode->i_mutex);
635	dput(root);
636
637	if (err) {
638		kfree(e);
639		return -EINVAL;
640	}
641	return count;
642}
643
644static const struct file_operations bm_register_operations = {
645	.write		= bm_register_write,
646};
647
648/* /status */
649
650static ssize_t
651bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
652{
653	char *s = enabled ? "enabled\n" : "disabled\n";
654
655	return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
656}
657
658static ssize_t bm_status_write(struct file * file, const char __user * buffer,
659		size_t count, loff_t *ppos)
660{
661	int res = parse_command(buffer, count);
662	struct dentry *root;
663
664	switch (res) {
665		case 1: enabled = 0; break;
666		case 2: enabled = 1; break;
667		case 3: root = dget(file->f_path.mnt->mnt_sb->s_root);
668			mutex_lock(&root->d_inode->i_mutex);
669
670			while (!list_empty(&entries))
671				kill_node(list_entry(entries.next, Node, list));
672
673			mutex_unlock(&root->d_inode->i_mutex);
674			dput(root);
675		default: return res;
676	}
677	return count;
678}
679
680static const struct file_operations bm_status_operations = {
681	.read		= bm_status_read,
682	.write		= bm_status_write,
683};
684
685/* Superblock handling */
686
687static const struct super_operations s_ops = {
688	.statfs		= simple_statfs,
689	.evict_inode	= bm_evict_inode,
690};
691
692static int bm_fill_super(struct super_block * sb, void * data, int silent)
693{
694	static struct tree_descr bm_files[] = {
695		[2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
696		[3] = {"register", &bm_register_operations, S_IWUSR},
697		/* last one */ {""}
698	};
699	int err = simple_fill_super(sb, 0x42494e4d, bm_files);
700	if (!err)
701		sb->s_op = &s_ops;
702	return err;
703}
704
705static int bm_get_sb(struct file_system_type *fs_type,
706	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
707{
708	return get_sb_single(fs_type, flags, data, bm_fill_super, mnt);
709}
710
711static struct linux_binfmt misc_format = {
712	.module = THIS_MODULE,
713	.load_binary = load_misc_binary,
714};
715
716static struct file_system_type bm_fs_type = {
717	.owner		= THIS_MODULE,
718	.name		= "binfmt_misc",
719	.get_sb		= bm_get_sb,
720	.kill_sb	= kill_litter_super,
721};
722
723static int __init init_misc_binfmt(void)
724{
725	int err = register_filesystem(&bm_fs_type);
726	if (!err) {
727		err = insert_binfmt(&misc_format);
728		if (err)
729			unregister_filesystem(&bm_fs_type);
730	}
731	return err;
732}
733
734static void __exit exit_misc_binfmt(void)
735{
736	unregister_binfmt(&misc_format);
737	unregister_filesystem(&bm_fs_type);
738}
739
740core_initcall(init_misc_binfmt);
741module_exit(exit_misc_binfmt);
742MODULE_LICENSE("GPL");
743