Root/fs/binfmt_misc.c

Source at commit 9845c1745d3d531a5b9544f5322c62bfb4d4e9bc created 1 year 2 months ago.
By Xiangfu, rtc: jz4740 fix hwclock give time out
1/*
2 * binfmt_misc.c
3 *
4 * Copyright (C) 1997 Richard Günther
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        would_dump(bprm, bprm->file);
153
154        allow_write_access(bprm->file);
155        bprm->file = NULL;
156
157        /* mark the bprm that fd should be passed to interp */
158        bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
159        bprm->interp_data = fd_binary;
160
161     } else {
162         allow_write_access(bprm->file);
163         fput(bprm->file);
164         bprm->file = NULL;
165     }
166    /* make argv[1] be the path to the binary */
167    retval = copy_strings_kernel (1, &bprm->interp, bprm);
168    if (retval < 0)
169        goto _error;
170    bprm->argc++;
171
172    /* add the interp as argv[0] */
173    retval = copy_strings_kernel (1, &iname_addr, bprm);
174    if (retval < 0)
175        goto _error;
176    bprm->argc ++;
177
178    bprm->interp = iname; /* for binfmt_script */
179
180    interp_file = open_exec (iname);
181    retval = PTR_ERR (interp_file);
182    if (IS_ERR (interp_file))
183        goto _error;
184
185    bprm->file = interp_file;
186    if (fmt->flags & MISC_FMT_CREDENTIALS) {
187        /*
188         * No need to call prepare_binprm(), it's already been
189         * done. bprm->buf is stale, update from interp_file.
190         */
191        memset(bprm->buf, 0, BINPRM_BUF_SIZE);
192        retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
193    } else
194        retval = prepare_binprm (bprm);
195
196    if (retval < 0)
197        goto _error;
198
199    bprm->recursion_depth++;
200
201    retval = search_binary_handler (bprm, regs);
202    if (retval < 0)
203        goto _error;
204
205_ret:
206    return retval;
207_error:
208    if (fd_binary > 0)
209        sys_close(fd_binary);
210    bprm->interp_flags = 0;
211    bprm->interp_data = 0;
212    goto _ret;
213}
214
215/* Command parsers */
216
217/*
218 * parses and copies one argument enclosed in del from *sp to *dp,
219 * recognising the \x special.
220 * returns pointer to the copied argument or NULL in case of an
221 * error (and sets err) or null argument length.
222 */
223static char *scanarg(char *s, char del)
224{
225    char c;
226
227    while ((c = *s++) != del) {
228        if (c == '\\' && *s == 'x') {
229            s++;
230            if (!isxdigit(*s++))
231                return NULL;
232            if (!isxdigit(*s++))
233                return NULL;
234        }
235    }
236    return s;
237}
238
239static int unquote(char *from)
240{
241    char c = 0, *s = from, *p = from;
242
243    while ((c = *s++) != '\0') {
244        if (c == '\\' && *s == 'x') {
245            s++;
246            c = toupper(*s++);
247            *p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
248            c = toupper(*s++);
249            *p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
250            continue;
251        }
252        *p++ = c;
253    }
254    return p - from;
255}
256
257static char * check_special_flags (char * sfs, Node * e)
258{
259    char * p = sfs;
260    int cont = 1;
261
262    /* special flags */
263    while (cont) {
264        switch (*p) {
265            case 'P':
266                p++;
267                e->flags |= MISC_FMT_PRESERVE_ARGV0;
268                break;
269            case 'O':
270                p++;
271                e->flags |= MISC_FMT_OPEN_BINARY;
272                break;
273            case 'C':
274                p++;
275                /* this flags also implies the
276                   open-binary flag */
277                e->flags |= (MISC_FMT_CREDENTIALS |
278                        MISC_FMT_OPEN_BINARY);
279                break;
280            default:
281                cont = 0;
282        }
283    }
284
285    return p;
286}
287/*
288 * This registers a new binary format, it recognises the syntax
289 * ':name:type:offset:magic:mask:interpreter:flags'
290 * where the ':' is the IFS, that can be chosen with the first char
291 */
292static Node *create_entry(const char __user *buffer, size_t count)
293{
294    Node *e;
295    int memsize, err;
296    char *buf, *p;
297    char del;
298
299    /* some sanity checks */
300    err = -EINVAL;
301    if ((count < 11) || (count > 256))
302        goto out;
303
304    err = -ENOMEM;
305    memsize = sizeof(Node) + count + 8;
306    e = kmalloc(memsize, GFP_USER);
307    if (!e)
308        goto out;
309
310    p = buf = (char *)e + sizeof(Node);
311
312    memset(e, 0, sizeof(Node));
313    if (copy_from_user(buf, buffer, count))
314        goto Efault;
315
316    del = *p++; /* delimeter */
317
318    memset(buf+count, del, 8);
319
320    e->name = p;
321    p = strchr(p, del);
322    if (!p)
323        goto Einval;
324    *p++ = '\0';
325    if (!e->name[0] ||
326        !strcmp(e->name, ".") ||
327        !strcmp(e->name, "..") ||
328        strchr(e->name, '/'))
329        goto Einval;
330    switch (*p++) {
331        case 'E': e->flags = 1<<Enabled; break;
332        case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
333        default: goto Einval;
334    }
335    if (*p++ != del)
336        goto Einval;
337    if (test_bit(Magic, &e->flags)) {
338        char *s = strchr(p, del);
339        if (!s)
340            goto Einval;
341        *s++ = '\0';
342        e->offset = simple_strtoul(p, &p, 10);
343        if (*p++)
344            goto Einval;
345        e->magic = p;
346        p = scanarg(p, del);
347        if (!p)
348            goto Einval;
349        p[-1] = '\0';
350        if (!e->magic[0])
351            goto Einval;
352        e->mask = p;
353        p = scanarg(p, del);
354        if (!p)
355            goto Einval;
356        p[-1] = '\0';
357        if (!e->mask[0])
358            e->mask = NULL;
359        e->size = unquote(e->magic);
360        if (e->mask && unquote(e->mask) != e->size)
361            goto Einval;
362        if (e->size + e->offset > BINPRM_BUF_SIZE)
363            goto Einval;
364    } else {
365        p = strchr(p, del);
366        if (!p)
367            goto Einval;
368        *p++ = '\0';
369        e->magic = p;
370        p = strchr(p, del);
371        if (!p)
372            goto Einval;
373        *p++ = '\0';
374        if (!e->magic[0] || strchr(e->magic, '/'))
375            goto Einval;
376        p = strchr(p, del);
377        if (!p)
378            goto Einval;
379        *p++ = '\0';
380    }
381    e->interpreter = p;
382    p = strchr(p, del);
383    if (!p)
384        goto Einval;
385    *p++ = '\0';
386    if (!e->interpreter[0])
387        goto Einval;
388
389
390    p = check_special_flags (p, e);
391
392    if (*p == '\n')
393        p++;
394    if (p != buf + count)
395        goto Einval;
396    return e;
397
398out:
399    return ERR_PTR(err);
400
401Efault:
402    kfree(e);
403    return ERR_PTR(-EFAULT);
404Einval:
405    kfree(e);
406    return ERR_PTR(-EINVAL);
407}
408
409/*
410 * Set status of entry/binfmt_misc:
411 * '1' enables, '0' disables and '-1' clears entry/binfmt_misc
412 */
413static int parse_command(const char __user *buffer, size_t count)
414{
415    char s[4];
416
417    if (!count)
418        return 0;
419    if (count > 3)
420        return -EINVAL;
421    if (copy_from_user(s, buffer, count))
422        return -EFAULT;
423    if (s[count-1] == '\n')
424        count--;
425    if (count == 1 && s[0] == '0')
426        return 1;
427    if (count == 1 && s[0] == '1')
428        return 2;
429    if (count == 2 && s[0] == '-' && s[1] == '1')
430        return 3;
431    return -EINVAL;
432}
433
434/* generic stuff */
435
436static void entry_status(Node *e, char *page)
437{
438    char *dp;
439    char *status = "disabled";
440    const char * flags = "flags: ";
441
442    if (test_bit(Enabled, &e->flags))
443        status = "enabled";
444
445    if (!VERBOSE_STATUS) {
446        sprintf(page, "%s\n", status);
447        return;
448    }
449
450    sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
451    dp = page + strlen(page);
452
453    /* print the special flags */
454    sprintf (dp, "%s", flags);
455    dp += strlen (flags);
456    if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
457        *dp ++ = 'P';
458    }
459    if (e->flags & MISC_FMT_OPEN_BINARY) {
460        *dp ++ = 'O';
461    }
462    if (e->flags & MISC_FMT_CREDENTIALS) {
463        *dp ++ = 'C';
464    }
465    *dp ++ = '\n';
466
467
468    if (!test_bit(Magic, &e->flags)) {
469        sprintf(dp, "extension .%s\n", e->magic);
470    } else {
471        int i;
472
473        sprintf(dp, "offset %i\nmagic ", e->offset);
474        dp = page + strlen(page);
475        for (i = 0; i < e->size; i++) {
476            sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
477            dp += 2;
478        }
479        if (e->mask) {
480            sprintf(dp, "\nmask ");
481            dp += 6;
482            for (i = 0; i < e->size; i++) {
483                sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
484                dp += 2;
485            }
486        }
487        *dp++ = '\n';
488        *dp = '\0';
489    }
490}
491
492static struct inode *bm_get_inode(struct super_block *sb, int mode)
493{
494    struct inode * inode = new_inode(sb);
495
496    if (inode) {
497        inode->i_ino = get_next_ino();
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        drop_nlink(dentry->d_inode);
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    .llseek = default_llseek,
580};
581
582/* /register */
583
584static ssize_t bm_register_write(struct file *file, const char __user *buffer,
585                   size_t count, loff_t *ppos)
586{
587    Node *e;
588    struct inode *inode;
589    struct dentry *root, *dentry;
590    struct super_block *sb = file->f_path.mnt->mnt_sb;
591    int err = 0;
592
593    e = create_entry(buffer, count);
594
595    if (IS_ERR(e))
596        return PTR_ERR(e);
597
598    root = dget(sb->s_root);
599    mutex_lock(&root->d_inode->i_mutex);
600    dentry = lookup_one_len(e->name, root, strlen(e->name));
601    err = PTR_ERR(dentry);
602    if (IS_ERR(dentry))
603        goto out;
604
605    err = -EEXIST;
606    if (dentry->d_inode)
607        goto out2;
608
609    inode = bm_get_inode(sb, S_IFREG | 0644);
610
611    err = -ENOMEM;
612    if (!inode)
613        goto out2;
614
615    err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
616    if (err) {
617        iput(inode);
618        inode = NULL;
619        goto out2;
620    }
621
622    e->dentry = dget(dentry);
623    inode->i_private = e;
624    inode->i_fop = &bm_entry_operations;
625
626    d_instantiate(dentry, inode);
627    write_lock(&entries_lock);
628    list_add(&e->list, &entries);
629    write_unlock(&entries_lock);
630
631    err = 0;
632out2:
633    dput(dentry);
634out:
635    mutex_unlock(&root->d_inode->i_mutex);
636    dput(root);
637
638    if (err) {
639        kfree(e);
640        return -EINVAL;
641    }
642    return count;
643}
644
645static const struct file_operations bm_register_operations = {
646    .write = bm_register_write,
647    .llseek = noop_llseek,
648};
649
650/* /status */
651
652static ssize_t
653bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
654{
655    char *s = enabled ? "enabled\n" : "disabled\n";
656
657    return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
658}
659
660static ssize_t bm_status_write(struct file * file, const char __user * buffer,
661        size_t count, loff_t *ppos)
662{
663    int res = parse_command(buffer, count);
664    struct dentry *root;
665
666    switch (res) {
667        case 1: enabled = 0; break;
668        case 2: enabled = 1; break;
669        case 3: root = dget(file->f_path.mnt->mnt_sb->s_root);
670            mutex_lock(&root->d_inode->i_mutex);
671
672            while (!list_empty(&entries))
673                kill_node(list_entry(entries.next, Node, list));
674
675            mutex_unlock(&root->d_inode->i_mutex);
676            dput(root);
677        default: return res;
678    }
679    return count;
680}
681
682static const struct file_operations bm_status_operations = {
683    .read = bm_status_read,
684    .write = bm_status_write,
685    .llseek = default_llseek,
686};
687
688/* Superblock handling */
689
690static const struct super_operations s_ops = {
691    .statfs = simple_statfs,
692    .evict_inode = bm_evict_inode,
693};
694
695static int bm_fill_super(struct super_block * sb, void * data, int silent)
696{
697    static struct tree_descr bm_files[] = {
698        [2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
699        [3] = {"register", &bm_register_operations, S_IWUSR},
700        /* last one */ {""}
701    };
702    int err = simple_fill_super(sb, 0x42494e4d, bm_files);
703    if (!err)
704        sb->s_op = &s_ops;
705    return err;
706}
707
708static struct dentry *bm_mount(struct file_system_type *fs_type,
709    int flags, const char *dev_name, void *data)
710{
711    return mount_single(fs_type, flags, data, bm_fill_super);
712}
713
714static struct linux_binfmt misc_format = {
715    .module = THIS_MODULE,
716    .load_binary = load_misc_binary,
717};
718
719static struct file_system_type bm_fs_type = {
720    .owner = THIS_MODULE,
721    .name = "binfmt_misc",
722    .mount = bm_mount,
723    .kill_sb = kill_litter_super,
724};
725
726static int __init init_misc_binfmt(void)
727{
728    int err = register_filesystem(&bm_fs_type);
729    if (!err) {
730        err = insert_binfmt(&misc_format);
731        if (err)
732            unregister_filesystem(&bm_fs_type);
733    }
734    return err;
735}
736
737static void __exit exit_misc_binfmt(void)
738{
739    unregister_binfmt(&misc_format);
740    unregister_filesystem(&bm_fs_type);
741}
742
743core_initcall(init_misc_binfmt);
744module_exit(exit_misc_binfmt);
745MODULE_LICENSE("GPL");
746

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