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1 /*
2  * AppArmor security module
3  *
4  * This file contains AppArmor mediation of files
5  *
6  * Copyright (C) 1998-2008 Novell/SUSE
7  * Copyright 2009-2010 Canonical Ltd.
8  *
9  * This program is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU General Public License as
11  * published by the Free Software Foundation, version 2 of the
12  * License.
13  */
14 
15 #include <linux/tty.h>
16 #include <linux/fdtable.h>
17 #include <linux/file.h>
18 
19 #include "include/apparmor.h"
20 #include "include/audit.h"
21 #include "include/context.h"
22 #include "include/file.h"
23 #include "include/match.h"
24 #include "include/path.h"
25 #include "include/policy.h"
26 #include "include/label.h"
27 
map_mask_to_chr_mask(u32 mask)28 static u32 map_mask_to_chr_mask(u32 mask)
29 {
30 	u32 m = mask & PERMS_CHRS_MASK;
31 
32 	if (mask & AA_MAY_GETATTR)
33 		m |= MAY_READ;
34 	if (mask & (AA_MAY_SETATTR | AA_MAY_CHMOD | AA_MAY_CHOWN))
35 		m |= MAY_WRITE;
36 
37 	return m;
38 }
39 
40 /**
41  * audit_file_mask - convert mask to permission string
42  * @buffer: buffer to write string to (NOT NULL)
43  * @mask: permission mask to convert
44  */
audit_file_mask(struct audit_buffer * ab,u32 mask)45 static void audit_file_mask(struct audit_buffer *ab, u32 mask)
46 {
47 	char str[10];
48 
49 	aa_perm_mask_to_str(str, aa_file_perm_chrs, map_mask_to_chr_mask(mask));
50 	audit_log_string(ab, str);
51 }
52 
53 /**
54  * file_audit_cb - call back for file specific audit fields
55  * @ab: audit_buffer  (NOT NULL)
56  * @va: audit struct to audit values of  (NOT NULL)
57  */
file_audit_cb(struct audit_buffer * ab,void * va)58 static void file_audit_cb(struct audit_buffer *ab, void *va)
59 {
60 	struct common_audit_data *sa = va;
61 	kuid_t fsuid = current_fsuid();
62 
63 	if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
64 		audit_log_format(ab, " requested_mask=");
65 		audit_file_mask(ab, aad(sa)->request);
66 	}
67 	if (aad(sa)->denied & AA_AUDIT_FILE_MASK) {
68 		audit_log_format(ab, " denied_mask=");
69 		audit_file_mask(ab, aad(sa)->denied);
70 	}
71 	if (aad(sa)->request & AA_AUDIT_FILE_MASK) {
72 		audit_log_format(ab, " fsuid=%d",
73 				 from_kuid(&init_user_ns, fsuid));
74 		audit_log_format(ab, " ouid=%d",
75 				 from_kuid(&init_user_ns, aad(sa)->fs.ouid));
76 	}
77 
78 	if (aad(sa)->peer) {
79 		audit_log_format(ab, " target=");
80 		aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
81 				FLAG_VIEW_SUBNS, GFP_ATOMIC);
82 	} else if (aad(sa)->fs.target) {
83 		audit_log_format(ab, " target=");
84 		audit_log_untrustedstring(ab, aad(sa)->fs.target);
85 	}
86 }
87 
88 /**
89  * aa_audit_file - handle the auditing of file operations
90  * @profile: the profile being enforced  (NOT NULL)
91  * @perms: the permissions computed for the request (NOT NULL)
92  * @op: operation being mediated
93  * @request: permissions requested
94  * @name: name of object being mediated (MAYBE NULL)
95  * @target: name of target (MAYBE NULL)
96  * @tlabel: target label (MAY BE NULL)
97  * @ouid: object uid
98  * @info: extra information message (MAYBE NULL)
99  * @error: 0 if operation allowed else failure error code
100  *
101  * Returns: %0 or error on failure
102  */
aa_audit_file(struct aa_profile * profile,struct aa_perms * perms,const char * op,u32 request,const char * name,const char * target,struct aa_label * tlabel,kuid_t ouid,const char * info,int error)103 int aa_audit_file(struct aa_profile *profile, struct aa_perms *perms,
104 		  const char *op, u32 request, const char *name,
105 		  const char *target, struct aa_label *tlabel,
106 		  kuid_t ouid, const char *info, int error)
107 {
108 	int type = AUDIT_APPARMOR_AUTO;
109 	DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_TASK, op);
110 
111 	sa.u.tsk = NULL;
112 	aad(&sa)->request = request;
113 	aad(&sa)->name = name;
114 	aad(&sa)->fs.target = target;
115 	aad(&sa)->peer = tlabel;
116 	aad(&sa)->fs.ouid = ouid;
117 	aad(&sa)->info = info;
118 	aad(&sa)->error = error;
119 	sa.u.tsk = NULL;
120 
121 	if (likely(!aad(&sa)->error)) {
122 		u32 mask = perms->audit;
123 
124 		if (unlikely(AUDIT_MODE(profile) == AUDIT_ALL))
125 			mask = 0xffff;
126 
127 		/* mask off perms that are not being force audited */
128 		aad(&sa)->request &= mask;
129 
130 		if (likely(!aad(&sa)->request))
131 			return 0;
132 		type = AUDIT_APPARMOR_AUDIT;
133 	} else {
134 		/* only report permissions that were denied */
135 		aad(&sa)->request = aad(&sa)->request & ~perms->allow;
136 		AA_BUG(!aad(&sa)->request);
137 
138 		if (aad(&sa)->request & perms->kill)
139 			type = AUDIT_APPARMOR_KILL;
140 
141 		/* quiet known rejects, assumes quiet and kill do not overlap */
142 		if ((aad(&sa)->request & perms->quiet) &&
143 		    AUDIT_MODE(profile) != AUDIT_NOQUIET &&
144 		    AUDIT_MODE(profile) != AUDIT_ALL)
145 			aad(&sa)->request &= ~perms->quiet;
146 
147 		if (!aad(&sa)->request)
148 			return aad(&sa)->error;
149 	}
150 
151 	aad(&sa)->denied = aad(&sa)->request & ~perms->allow;
152 	return aa_audit(type, profile, &sa, file_audit_cb);
153 }
154 
155 /**
156  * is_deleted - test if a file has been completely unlinked
157  * @dentry: dentry of file to test for deletion  (NOT NULL)
158  *
159  * Returns: %1 if deleted else %0
160  */
is_deleted(struct dentry * dentry)161 static inline bool is_deleted(struct dentry *dentry)
162 {
163 	if (d_unlinked(dentry) && d_backing_inode(dentry)->i_nlink == 0)
164 		return 1;
165 	return 0;
166 }
167 
path_name(const char * op,struct aa_label * label,const struct path * path,int flags,char * buffer,const char ** name,struct path_cond * cond,u32 request)168 static int path_name(const char *op, struct aa_label *label,
169 		     const struct path *path, int flags, char *buffer,
170 		     const char **name, struct path_cond *cond, u32 request)
171 {
172 	struct aa_profile *profile;
173 	const char *info = NULL;
174 	int error;
175 
176 	error = aa_path_name(path, flags, buffer, name, &info,
177 			     labels_profile(label)->disconnected);
178 	if (error) {
179 		fn_for_each_confined(label, profile,
180 			aa_audit_file(profile, &nullperms, op, request, *name,
181 				      NULL, NULL, cond->uid, info, error));
182 		return error;
183 	}
184 
185 	return 0;
186 }
187 
188 /**
189  * map_old_perms - map old file perms layout to the new layout
190  * @old: permission set in old mapping
191  *
192  * Returns: new permission mapping
193  */
map_old_perms(u32 old)194 static u32 map_old_perms(u32 old)
195 {
196 	u32 new = old & 0xf;
197 	if (old & MAY_READ)
198 		new |= AA_MAY_GETATTR | AA_MAY_OPEN;
199 	if (old & MAY_WRITE)
200 		new |= AA_MAY_SETATTR | AA_MAY_CREATE | AA_MAY_DELETE |
201 		       AA_MAY_CHMOD | AA_MAY_CHOWN | AA_MAY_OPEN;
202 	if (old & 0x10)
203 		new |= AA_MAY_LINK;
204 	/* the old mapping lock and link_subset flags where overlaid
205 	 * and use was determined by part of a pair that they were in
206 	 */
207 	if (old & 0x20)
208 		new |= AA_MAY_LOCK | AA_LINK_SUBSET;
209 	if (old & 0x40)	/* AA_EXEC_MMAP */
210 		new |= AA_EXEC_MMAP;
211 
212 	return new;
213 }
214 
215 /**
216  * aa_compute_fperms - convert dfa compressed perms to internal perms
217  * @dfa: dfa to compute perms for   (NOT NULL)
218  * @state: state in dfa
219  * @cond:  conditions to consider  (NOT NULL)
220  *
221  * TODO: convert from dfa + state to permission entry, do computation conversion
222  *       at load time.
223  *
224  * Returns: computed permission set
225  */
aa_compute_fperms(struct aa_dfa * dfa,unsigned int state,struct path_cond * cond)226 struct aa_perms aa_compute_fperms(struct aa_dfa *dfa, unsigned int state,
227 				  struct path_cond *cond)
228 {
229 	struct aa_perms perms;
230 
231 	/* FIXME: change over to new dfa format
232 	 * currently file perms are encoded in the dfa, new format
233 	 * splits the permissions from the dfa.  This mapping can be
234 	 * done at profile load
235 	 */
236 	perms.deny = 0;
237 	perms.kill = perms.stop = 0;
238 	perms.complain = perms.cond = 0;
239 	perms.hide = 0;
240 	perms.prompt = 0;
241 
242 	if (uid_eq(current_fsuid(), cond->uid)) {
243 		perms.allow = map_old_perms(dfa_user_allow(dfa, state));
244 		perms.audit = map_old_perms(dfa_user_audit(dfa, state));
245 		perms.quiet = map_old_perms(dfa_user_quiet(dfa, state));
246 		perms.xindex = dfa_user_xindex(dfa, state);
247 	} else {
248 		perms.allow = map_old_perms(dfa_other_allow(dfa, state));
249 		perms.audit = map_old_perms(dfa_other_audit(dfa, state));
250 		perms.quiet = map_old_perms(dfa_other_quiet(dfa, state));
251 		perms.xindex = dfa_other_xindex(dfa, state);
252 	}
253 	perms.allow |= AA_MAY_GETATTR;
254 
255 	/* change_profile wasn't determined by ownership in old mapping */
256 	if (ACCEPT_TABLE(dfa)[state] & 0x80000000)
257 		perms.allow |= AA_MAY_CHANGE_PROFILE;
258 	if (ACCEPT_TABLE(dfa)[state] & 0x40000000)
259 		perms.allow |= AA_MAY_ONEXEC;
260 
261 	return perms;
262 }
263 
264 /**
265  * aa_str_perms - find permission that match @name
266  * @dfa: to match against  (MAYBE NULL)
267  * @state: state to start matching in
268  * @name: string to match against dfa  (NOT NULL)
269  * @cond: conditions to consider for permission set computation  (NOT NULL)
270  * @perms: Returns - the permissions found when matching @name
271  *
272  * Returns: the final state in @dfa when beginning @start and walking @name
273  */
aa_str_perms(struct aa_dfa * dfa,unsigned int start,const char * name,struct path_cond * cond,struct aa_perms * perms)274 unsigned int aa_str_perms(struct aa_dfa *dfa, unsigned int start,
275 			  const char *name, struct path_cond *cond,
276 			  struct aa_perms *perms)
277 {
278 	unsigned int state;
279 	state = aa_dfa_match(dfa, start, name);
280 	*perms = aa_compute_fperms(dfa, state, cond);
281 
282 	return state;
283 }
284 
__aa_path_perm(const char * op,struct aa_profile * profile,const char * name,u32 request,struct path_cond * cond,int flags,struct aa_perms * perms)285 int __aa_path_perm(const char *op, struct aa_profile *profile, const char *name,
286 		   u32 request, struct path_cond *cond, int flags,
287 		   struct aa_perms *perms)
288 {
289 	int e = 0;
290 
291 	if (profile_unconfined(profile))
292 		return 0;
293 	aa_str_perms(profile->file.dfa, profile->file.start, name, cond, perms);
294 	if (request & ~perms->allow)
295 		e = -EACCES;
296 	return aa_audit_file(profile, perms, op, request, name, NULL, NULL,
297 			     cond->uid, NULL, e);
298 }
299 
300 
profile_path_perm(const char * op,struct aa_profile * profile,const struct path * path,char * buffer,u32 request,struct path_cond * cond,int flags,struct aa_perms * perms)301 static int profile_path_perm(const char *op, struct aa_profile *profile,
302 			     const struct path *path, char *buffer, u32 request,
303 			     struct path_cond *cond, int flags,
304 			     struct aa_perms *perms)
305 {
306 	const char *name;
307 	int error;
308 
309 	if (profile_unconfined(profile))
310 		return 0;
311 
312 	error = path_name(op, &profile->label, path,
313 			  flags | profile->path_flags, buffer, &name, cond,
314 			  request);
315 	if (error)
316 		return error;
317 	return __aa_path_perm(op, profile, name, request, cond, flags,
318 			      perms);
319 }
320 
321 /**
322  * aa_path_perm - do permissions check & audit for @path
323  * @op: operation being checked
324  * @label: profile being enforced  (NOT NULL)
325  * @path: path to check permissions of  (NOT NULL)
326  * @flags: any additional path flags beyond what the profile specifies
327  * @request: requested permissions
328  * @cond: conditional info for this request  (NOT NULL)
329  *
330  * Returns: %0 else error if access denied or other error
331  */
aa_path_perm(const char * op,struct aa_label * label,const struct path * path,int flags,u32 request,struct path_cond * cond)332 int aa_path_perm(const char *op, struct aa_label *label,
333 		 const struct path *path, int flags, u32 request,
334 		 struct path_cond *cond)
335 {
336 	struct aa_perms perms = {};
337 	struct aa_profile *profile;
338 	char *buffer = NULL;
339 	int error;
340 
341 	flags |= PATH_DELEGATE_DELETED | (S_ISDIR(cond->mode) ? PATH_IS_DIR :
342 								0);
343 	get_buffers(buffer);
344 	error = fn_for_each_confined(label, profile,
345 			profile_path_perm(op, profile, path, buffer, request,
346 					  cond, flags, &perms));
347 
348 	put_buffers(buffer);
349 
350 	return error;
351 }
352 
353 /**
354  * xindex_is_subset - helper for aa_path_link
355  * @link: link permission set
356  * @target: target permission set
357  *
358  * test target x permissions are equal OR a subset of link x permissions
359  * this is done as part of the subset test, where a hardlink must have
360  * a subset of permissions that the target has.
361  *
362  * Returns: %1 if subset else %0
363  */
xindex_is_subset(u32 link,u32 target)364 static inline bool xindex_is_subset(u32 link, u32 target)
365 {
366 	if (((link & ~AA_X_UNSAFE) != (target & ~AA_X_UNSAFE)) ||
367 	    ((link & AA_X_UNSAFE) && !(target & AA_X_UNSAFE)))
368 		return 0;
369 
370 	return 1;
371 }
372 
profile_path_link(struct aa_profile * profile,const struct path * link,char * buffer,const struct path * target,char * buffer2,struct path_cond * cond)373 static int profile_path_link(struct aa_profile *profile,
374 			     const struct path *link, char *buffer,
375 			     const struct path *target, char *buffer2,
376 			     struct path_cond *cond)
377 {
378 	const char *lname, *tname = NULL;
379 	struct aa_perms lperms = {}, perms;
380 	const char *info = NULL;
381 	u32 request = AA_MAY_LINK;
382 	unsigned int state;
383 	int error;
384 
385 	error = path_name(OP_LINK, &profile->label, link, profile->path_flags,
386 			  buffer, &lname, cond, AA_MAY_LINK);
387 	if (error)
388 		goto audit;
389 
390 	/* buffer2 freed below, tname is pointer in buffer2 */
391 	error = path_name(OP_LINK, &profile->label, target, profile->path_flags,
392 			  buffer2, &tname, cond, AA_MAY_LINK);
393 	if (error)
394 		goto audit;
395 
396 	error = -EACCES;
397 	/* aa_str_perms - handles the case of the dfa being NULL */
398 	state = aa_str_perms(profile->file.dfa, profile->file.start, lname,
399 			     cond, &lperms);
400 
401 	if (!(lperms.allow & AA_MAY_LINK))
402 		goto audit;
403 
404 	/* test to see if target can be paired with link */
405 	state = aa_dfa_null_transition(profile->file.dfa, state);
406 	aa_str_perms(profile->file.dfa, state, tname, cond, &perms);
407 
408 	/* force audit/quiet masks for link are stored in the second entry
409 	 * in the link pair.
410 	 */
411 	lperms.audit = perms.audit;
412 	lperms.quiet = perms.quiet;
413 	lperms.kill = perms.kill;
414 
415 	if (!(perms.allow & AA_MAY_LINK)) {
416 		info = "target restricted";
417 		lperms = perms;
418 		goto audit;
419 	}
420 
421 	/* done if link subset test is not required */
422 	if (!(perms.allow & AA_LINK_SUBSET))
423 		goto done_tests;
424 
425 	/* Do link perm subset test requiring allowed permission on link are
426 	 * a subset of the allowed permissions on target.
427 	 */
428 	aa_str_perms(profile->file.dfa, profile->file.start, tname, cond,
429 		     &perms);
430 
431 	/* AA_MAY_LINK is not considered in the subset test */
432 	request = lperms.allow & ~AA_MAY_LINK;
433 	lperms.allow &= perms.allow | AA_MAY_LINK;
434 
435 	request |= AA_AUDIT_FILE_MASK & (lperms.allow & ~perms.allow);
436 	if (request & ~lperms.allow) {
437 		goto audit;
438 	} else if ((lperms.allow & MAY_EXEC) &&
439 		   !xindex_is_subset(lperms.xindex, perms.xindex)) {
440 		lperms.allow &= ~MAY_EXEC;
441 		request |= MAY_EXEC;
442 		info = "link not subset of target";
443 		goto audit;
444 	}
445 
446 done_tests:
447 	error = 0;
448 
449 audit:
450 	return aa_audit_file(profile, &lperms, OP_LINK, request, lname, tname,
451 			     NULL, cond->uid, info, error);
452 }
453 
454 /**
455  * aa_path_link - Handle hard link permission check
456  * @label: the label being enforced  (NOT NULL)
457  * @old_dentry: the target dentry  (NOT NULL)
458  * @new_dir: directory the new link will be created in  (NOT NULL)
459  * @new_dentry: the link being created  (NOT NULL)
460  *
461  * Handle the permission test for a link & target pair.  Permission
462  * is encoded as a pair where the link permission is determined
463  * first, and if allowed, the target is tested.  The target test
464  * is done from the point of the link match (not start of DFA)
465  * making the target permission dependent on the link permission match.
466  *
467  * The subset test if required forces that permissions granted
468  * on link are a subset of the permission granted to target.
469  *
470  * Returns: %0 if allowed else error
471  */
aa_path_link(struct aa_label * label,struct dentry * old_dentry,const struct path * new_dir,struct dentry * new_dentry)472 int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
473 		 const struct path *new_dir, struct dentry *new_dentry)
474 {
475 	struct path link = { .mnt = new_dir->mnt, .dentry = new_dentry };
476 	struct path target = { .mnt = new_dir->mnt, .dentry = old_dentry };
477 	struct path_cond cond = {
478 		d_backing_inode(old_dentry)->i_uid,
479 		d_backing_inode(old_dentry)->i_mode
480 	};
481 	char *buffer = NULL, *buffer2 = NULL;
482 	struct aa_profile *profile;
483 	int error;
484 
485 	/* buffer freed below, lname is pointer in buffer */
486 	get_buffers(buffer, buffer2);
487 	error = fn_for_each_confined(label, profile,
488 			profile_path_link(profile, &link, buffer, &target,
489 					  buffer2, &cond));
490 	put_buffers(buffer, buffer2);
491 
492 	return error;
493 }
494 
update_file_ctx(struct aa_file_ctx * fctx,struct aa_label * label,u32 request)495 static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
496 			    u32 request)
497 {
498 	struct aa_label *l, *old;
499 
500 	/* update caching of label on file_ctx */
501 	spin_lock(&fctx->lock);
502 	old = rcu_dereference_protected(fctx->label,
503 					spin_is_locked(&fctx->lock));
504 	l = aa_label_merge(old, label, GFP_ATOMIC);
505 	if (l) {
506 		if (l != old) {
507 			rcu_assign_pointer(fctx->label, l);
508 			aa_put_label(old);
509 		} else
510 			aa_put_label(l);
511 		fctx->allow |= request;
512 	}
513 	spin_unlock(&fctx->lock);
514 }
515 
__file_path_perm(const char * op,struct aa_label * label,struct aa_label * flabel,struct file * file,u32 request,u32 denied)516 static int __file_path_perm(const char *op, struct aa_label *label,
517 			    struct aa_label *flabel, struct file *file,
518 			    u32 request, u32 denied)
519 {
520 	struct aa_profile *profile;
521 	struct aa_perms perms = {};
522 	struct path_cond cond = {
523 		.uid = file_inode(file)->i_uid,
524 		.mode = file_inode(file)->i_mode
525 	};
526 	char *buffer;
527 	int flags, error;
528 
529 	/* revalidation due to label out of date. No revocation at this time */
530 	if (!denied && aa_label_is_subset(flabel, label))
531 		/* TODO: check for revocation on stale profiles */
532 		return 0;
533 
534 	flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
535 	get_buffers(buffer);
536 
537 	/* check every profile in task label not in current cache */
538 	error = fn_for_each_not_in_set(flabel, label, profile,
539 			profile_path_perm(op, profile, &file->f_path, buffer,
540 					  request, &cond, flags, &perms));
541 	if (denied && !error) {
542 		/*
543 		 * check every profile in file label that was not tested
544 		 * in the initial check above.
545 		 *
546 		 * TODO: cache full perms so this only happens because of
547 		 * conditionals
548 		 * TODO: don't audit here
549 		 */
550 		if (label == flabel)
551 			error = fn_for_each(label, profile,
552 				profile_path_perm(op, profile, &file->f_path,
553 						  buffer, request, &cond, flags,
554 						  &perms));
555 		else
556 			error = fn_for_each_not_in_set(label, flabel, profile,
557 				profile_path_perm(op, profile, &file->f_path,
558 						  buffer, request, &cond, flags,
559 						  &perms));
560 	}
561 	if (!error)
562 		update_file_ctx(file_ctx(file), label, request);
563 
564 	put_buffers(buffer);
565 
566 	return error;
567 }
568 
569 /**
570  * aa_file_perm - do permission revalidation check & audit for @file
571  * @op: operation being checked
572  * @label: label being enforced   (NOT NULL)
573  * @file: file to revalidate access permissions on  (NOT NULL)
574  * @request: requested permissions
575  *
576  * Returns: %0 if access allowed else error
577  */
aa_file_perm(const char * op,struct aa_label * label,struct file * file,u32 request)578 int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
579 		 u32 request)
580 {
581 	struct aa_file_ctx *fctx;
582 	struct aa_label *flabel;
583 	u32 denied;
584 	int error = 0;
585 
586 	AA_BUG(!label);
587 	AA_BUG(!file);
588 
589 	fctx = file_ctx(file);
590 
591 	rcu_read_lock();
592 	flabel  = rcu_dereference(fctx->label);
593 	AA_BUG(!flabel);
594 
595 	/* revalidate access, if task is unconfined, or the cached cred
596 	 * doesn't match or if the request is for more permissions than
597 	 * was granted.
598 	 *
599 	 * Note: the test for !unconfined(flabel) is to handle file
600 	 *       delegation from unconfined tasks
601 	 */
602 	denied = request & ~fctx->allow;
603 	if (unconfined(label) || unconfined(flabel) ||
604 	    (!denied && aa_label_is_subset(flabel, label)))
605 		goto done;
606 
607 	/* TODO: label cross check */
608 
609 	if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
610 		error = __file_path_perm(op, label, flabel, file, request,
611 					 denied);
612 
613 done:
614 	rcu_read_unlock();
615 
616 	return error;
617 }
618 
revalidate_tty(struct aa_label * label)619 static void revalidate_tty(struct aa_label *label)
620 {
621 	struct tty_struct *tty;
622 	int drop_tty = 0;
623 
624 	tty = get_current_tty();
625 	if (!tty)
626 		return;
627 
628 	spin_lock(&tty->files_lock);
629 	if (!list_empty(&tty->tty_files)) {
630 		struct tty_file_private *file_priv;
631 		struct file *file;
632 		/* TODO: Revalidate access to controlling tty. */
633 		file_priv = list_first_entry(&tty->tty_files,
634 					     struct tty_file_private, list);
635 		file = file_priv->file;
636 
637 		if (aa_file_perm(OP_INHERIT, label, file, MAY_READ | MAY_WRITE))
638 			drop_tty = 1;
639 	}
640 	spin_unlock(&tty->files_lock);
641 	tty_kref_put(tty);
642 
643 	if (drop_tty)
644 		no_tty();
645 }
646 
match_file(const void * p,struct file * file,unsigned int fd)647 static int match_file(const void *p, struct file *file, unsigned int fd)
648 {
649 	struct aa_label *label = (struct aa_label *)p;
650 
651 	if (aa_file_perm(OP_INHERIT, label, file, aa_map_file_to_perms(file)))
652 		return fd + 1;
653 	return 0;
654 }
655 
656 
657 /* based on selinux's flush_unauthorized_files */
aa_inherit_files(const struct cred * cred,struct files_struct * files)658 void aa_inherit_files(const struct cred *cred, struct files_struct *files)
659 {
660 	struct aa_label *label = aa_get_newest_cred_label(cred);
661 	struct file *devnull = NULL;
662 	unsigned int n;
663 
664 	revalidate_tty(label);
665 
666 	/* Revalidate access to inherited open files. */
667 	n = iterate_fd(files, 0, match_file, label);
668 	if (!n) /* none found? */
669 		goto out;
670 
671 	devnull = dentry_open(&aa_null, O_RDWR, cred);
672 	if (IS_ERR(devnull))
673 		devnull = NULL;
674 	/* replace all the matching ones with this */
675 	do {
676 		replace_fd(n - 1, devnull, 0);
677 	} while ((n = iterate_fd(files, n, match_file, label)) != 0);
678 	if (devnull)
679 		fput(devnull);
680 out:
681 	aa_put_label(label);
682 }
683