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2024-10-22 8ac6c7a54ed1b98d142dce24b11c6de6a1e239a5 
 kernel/fs/debugfs/inode.c
....@@ -2,12 +2,15 @@
22 /*
33  *  inode.c - part of debugfs, a tiny little debug file system
44  *
5
- *  Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
5
+ *  Copyright (C) 2004,2019 Greg Kroah-Hartman <greg@kroah.com>
66  *  Copyright (C) 2004 IBM Inc.
7
+ *  Copyright (C) 2019 Linux Foundation <gregkh@linuxfoundation.org>
78  *
89  *  debugfs is for people to use instead of /proc or /sys.
910  *  See ./Documentation/core-api/kernel-api.rst for more details.
1011  */
12
+
13
+#define pr_fmt(fmt)	"debugfs: " fmt
1114 
1215 #include <linux/module.h>
1316 #include <linux/fs.h>
....@@ -23,6 +26,7 @@
2326 #include <linux/parser.h>
2427 #include <linux/magic.h>
2528 #include <linux/slab.h>
29
+#include <linux/security.h>
2630 
2731 #include "internal.h"
2832 
....@@ -31,6 +35,33 @@
3135 static struct vfsmount *debugfs_mount;
3236 static int debugfs_mount_count;
3337 static bool debugfs_registered;
38
+static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
39
+
40
+/*
41
+ * Don't allow access attributes to be changed whilst the kernel is locked down
42
+ * so that we can use the file mode as part of a heuristic to determine whether
43
+ * to lock down individual files.
44
+ */
45
+static int debugfs_setattr(struct dentry *dentry, struct iattr *ia)
46
+{
47
+	int ret = security_locked_down(LOCKDOWN_DEBUGFS);
48
+
49
+	if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
50
+		return ret;
51
+	return simple_setattr(dentry, ia);
52
+}
53
+
54
+static const struct inode_operations debugfs_file_inode_operations = {
55
+	.setattr	= debugfs_setattr,
56
+};
57
+static const struct inode_operations debugfs_dir_inode_operations = {
58
+	.lookup		= simple_lookup,
59
+	.setattr	= debugfs_setattr,
60
+};
61
+static const struct inode_operations debugfs_symlink_inode_operations = {
62
+	.get_link	= simple_get_link,
63
+	.setattr	= debugfs_setattr,
64
+};
3465 
3566 static struct inode *debugfs_get_inode(struct super_block *sb)
3667 {
....@@ -163,24 +194,18 @@
163194 	return 0;
164195 }
165196 
166
-static void debugfs_i_callback(struct rcu_head *head)
197
+static void debugfs_free_inode(struct inode *inode)
167198 {
168
-	struct inode *inode = container_of(head, struct inode, i_rcu);
169199 	if (S_ISLNK(inode->i_mode))
170200 		kfree(inode->i_link);
171201 	free_inode_nonrcu(inode);
172
-}
173
-
174
-static void debugfs_destroy_inode(struct inode *inode)
175
-{
176
-	call_rcu(&inode->i_rcu, debugfs_i_callback);
177202 }
178203 
179204 static const struct super_operations debugfs_super_operations = {
180205 	.statfs		= simple_statfs,
181206 	.remount_fs	= debugfs_remount,
182207 	.show_options	= debugfs_show_options,
183
-	.destroy_inode	= debugfs_destroy_inode,
208
+	.free_inode	= debugfs_free_inode,
184209 };
185210 
186211 static void debugfs_release_dentry(struct dentry *dentry)
....@@ -242,6 +267,9 @@
242267 			int flags, const char *dev_name,
243268 			void *data)
244269 {
270
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API))
271
+		return ERR_PTR(-EPERM);
272
+
245273 	return mount_single(fs_type, flags, data, debug_fill_super);
246274 }
247275 
....@@ -269,19 +297,15 @@
269297 {
270298 	struct dentry *dentry;
271299 
272
-	if (IS_ERR(parent))
300
+	if (!debugfs_initialized() || IS_ERR_OR_NULL(name) || IS_ERR(parent))
273301 		return NULL;
274302 
275303 	if (!parent)
276304 		parent = debugfs_mount->mnt_root;
277305 
278
-	dentry = lookup_one_len_unlocked(name, parent, strlen(name));
306
+	dentry = lookup_positive_unlocked(name, parent, strlen(name));
279307 	if (IS_ERR(dentry))
280308 		return NULL;
281
-	if (!d_really_is_positive(dentry)) {
282
-		dput(dentry);
283
-		return NULL;
284
-	}
285309 	return dentry;
286310 }
287311 EXPORT_SYMBOL_GPL(debugfs_lookup);
....@@ -291,15 +315,23 @@
291315 	struct dentry *dentry;
292316 	int error;
293317 
294
-	pr_debug("debugfs: creating file '%s'\n",name);
318
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API))
319
+		return ERR_PTR(-EPERM);
320
+
321
+	if (!debugfs_initialized())
322
+		return ERR_PTR(-ENOENT);
323
+
324
+	pr_debug("creating file '%s'\n", name);
295325 
296326 	if (IS_ERR(parent))
297327 		return parent;
298328 
299329 	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
300330 			      &debugfs_mount_count);
301
-	if (error)
331
+	if (error) {
332
+		pr_err("Unable to pin filesystem for file '%s'\n", name);
302333 		return ERR_PTR(error);
334
+	}
303335 
304336 	/* If the parent is not specified, we create it in the root.
305337 	 * We need the root dentry to do this, which is in the super
....@@ -310,8 +342,17 @@
310342 		parent = debugfs_mount->mnt_root;
311343 
312344 	inode_lock(d_inode(parent));
313
-	dentry = lookup_one_len(name, parent, strlen(name));
345
+	if (unlikely(IS_DEADDIR(d_inode(parent))))
346
+		dentry = ERR_PTR(-ENOENT);
347
+	else
348
+		dentry = lookup_one_len(name, parent, strlen(name));
314349 	if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
350
+		if (d_is_dir(dentry))
351
+			pr_err("Directory '%s' with parent '%s' already present!\n",
352
+			       name, parent->d_name.name);
353
+		else
354
+			pr_err("File '%s' in directory '%s' already present!\n",
355
+			       name, parent->d_name.name);
315356 		dput(dentry);
316357 		dentry = ERR_PTR(-EEXIST);
317358 	}
....@@ -329,7 +370,7 @@
329370 	inode_unlock(d_inode(dentry->d_parent));
330371 	dput(dentry);
331372 	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
332
-	return NULL;
373
+	return ERR_PTR(-ENOMEM);
333374 }
334375 
335376 static struct dentry *end_creating(struct dentry *dentry)
....@@ -352,15 +393,24 @@
352393 	dentry = start_creating(name, parent);
353394 
354395 	if (IS_ERR(dentry))
355
-		return NULL;
396
+		return dentry;
397
+
398
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
399
+		failed_creating(dentry);
400
+		return ERR_PTR(-EPERM);
401
+	}
356402 
357403 	inode = debugfs_get_inode(dentry->d_sb);
358
-	if (unlikely(!inode))
404
+	if (unlikely(!inode)) {
405
+		pr_err("out of free dentries, can not create file '%s'\n",
406
+		       name);
359407 		return failed_creating(dentry);
408
+	}
360409 
361410 	inode->i_mode = mode;
362411 	inode->i_private = data;
363412 
413
+	inode->i_op = &debugfs_file_inode_operations;
364414 	inode->i_fop = proxy_fops;
365415 	dentry->d_fsdata = (void *)((unsigned long)real_fops |
366416 				DEBUGFS_FSDATA_IS_REAL_FOPS_BIT);
....@@ -391,7 +441,8 @@
391441  * This function will return a pointer to a dentry if it succeeds.  This
392442  * pointer must be passed to the debugfs_remove() function when the file is
393443  * to be removed (no automatic cleanup happens if your module is unloaded,
394
- * you are responsible here.)  If an error occurs, %NULL will be returned.
444
+ * you are responsible here.)  If an error occurs, ERR_PTR(-ERROR) will be
445
+ * returned.
395446  *
396447  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
397448  * returned.
....@@ -427,8 +478,8 @@
427478  * debugfs core.
428479  *
429480  * It is your responsibility to protect your struct file_operation
430
- * methods against file removals by means of debugfs_use_file_start()
431
- * and debugfs_use_file_finish(). ->open() is still protected by
481
+ * methods against file removals by means of debugfs_file_get()
482
+ * and debugfs_file_put(). ->open() is still protected by
432483  * debugfs though.
433484  *
434485  * Any struct file_operations defined by means of
....@@ -465,25 +516,16 @@
465516  * wide range of flexibility in creating a file, or a directory (if you want
466517  * to create a directory, the debugfs_create_dir() function is
467518  * recommended to be used instead.)
468
- *
469
- * This function will return a pointer to a dentry if it succeeds.  This
470
- * pointer must be passed to the debugfs_remove() function when the file is
471
- * to be removed (no automatic cleanup happens if your module is unloaded,
472
- * you are responsible here.)  If an error occurs, %NULL will be returned.
473
- *
474
- * If debugfs is not enabled in the kernel, the value -%ENODEV will be
475
- * returned.
476519  */
477
-struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
478
-					struct dentry *parent, void *data,
479
-					const struct file_operations *fops,
480
-					loff_t file_size)
520
+void debugfs_create_file_size(const char *name, umode_t mode,
521
+			      struct dentry *parent, void *data,
522
+			      const struct file_operations *fops,
523
+			      loff_t file_size)
481524 {
482525 	struct dentry *de = debugfs_create_file(name, mode, parent, data, fops);
483526 
484
-	if (de)
527
+	if (!IS_ERR(de))
485528 		d_inode(de)->i_size = file_size;
486
-	return de;
487529 }
488530 EXPORT_SYMBOL_GPL(debugfs_create_file_size);
489531 
....@@ -500,7 +542,8 @@
500542  * This function will return a pointer to a dentry if it succeeds.  This
501543  * pointer must be passed to the debugfs_remove() function when the file is
502544  * to be removed (no automatic cleanup happens if your module is unloaded,
503
- * you are responsible here.)  If an error occurs, %NULL will be returned.
545
+ * you are responsible here.)  If an error occurs, ERR_PTR(-ERROR) will be
546
+ * returned.
504547  *
505548  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
506549  * returned.
....@@ -511,14 +554,22 @@
511554 	struct inode *inode;
512555 
513556 	if (IS_ERR(dentry))
514
-		return NULL;
557
+		return dentry;
558
+
559
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
560
+		failed_creating(dentry);
561
+		return ERR_PTR(-EPERM);
562
+	}
515563 
516564 	inode = debugfs_get_inode(dentry->d_sb);
517
-	if (unlikely(!inode))
565
+	if (unlikely(!inode)) {
566
+		pr_err("out of free dentries, can not create directory '%s'\n",
567
+		       name);
518568 		return failed_creating(dentry);
569
+	}
519570 
520571 	inode->i_mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
521
-	inode->i_op = &simple_dir_inode_operations;
572
+	inode->i_op = &debugfs_dir_inode_operations;
522573 	inode->i_fop = &simple_dir_operations;
523574 
524575 	/* directory inodes start off with i_nlink == 2 (for "." entry) */
....@@ -550,11 +601,19 @@
550601 	struct inode *inode;
551602 
552603 	if (IS_ERR(dentry))
553
-		return NULL;
604
+		return dentry;
605
+
606
+	if (!(debugfs_allow & DEBUGFS_ALLOW_API)) {
607
+		failed_creating(dentry);
608
+		return ERR_PTR(-EPERM);
609
+	}
554610 
555611 	inode = debugfs_get_inode(dentry->d_sb);
556
-	if (unlikely(!inode))
612
+	if (unlikely(!inode)) {
613
+		pr_err("out of free dentries, can not create automount '%s'\n",
614
+		       name);
557615 		return failed_creating(dentry);
616
+	}
558617 
559618 	make_empty_dir_inode(inode);
560619 	inode->i_flags |= S_AUTOMOUNT;
....@@ -586,8 +645,8 @@
586645  * This function will return a pointer to a dentry if it succeeds.  This
587646  * pointer must be passed to the debugfs_remove() function when the symbolic
588647  * link is to be removed (no automatic cleanup happens if your module is
589
- * unloaded, you are responsible here.)  If an error occurs, %NULL will be
590
- * returned.
648
+ * unloaded, you are responsible here.)  If an error occurs, ERR_PTR(-ERROR)
649
+ * will be returned.
591650  *
592651  * If debugfs is not enabled in the kernel, the value -%ENODEV will be
593652  * returned.
....@@ -599,33 +658,32 @@
599658 	struct inode *inode;
600659 	char *link = kstrdup(target, GFP_KERNEL);
601660 	if (!link)
602
-		return NULL;
661
+		return ERR_PTR(-ENOMEM);
603662 
604663 	dentry = start_creating(name, parent);
605664 	if (IS_ERR(dentry)) {
606665 		kfree(link);
607
-		return NULL;
666
+		return dentry;
608667 	}
609668 
610669 	inode = debugfs_get_inode(dentry->d_sb);
611670 	if (unlikely(!inode)) {
671
+		pr_err("out of free dentries, can not create symlink '%s'\n",
672
+		       name);
612673 		kfree(link);
613674 		return failed_creating(dentry);
614675 	}
615676 	inode->i_mode = S_IFLNK | S_IRWXUGO;
616
-	inode->i_op = &simple_symlink_inode_operations;
677
+	inode->i_op = &debugfs_symlink_inode_operations;
617678 	inode->i_link = link;
618679 	d_instantiate(dentry, inode);
619680 	return end_creating(dentry);
620681 }
621682 EXPORT_SYMBOL_GPL(debugfs_create_symlink);
622683 
623
-static void __debugfs_remove_file(struct dentry *dentry, struct dentry *parent)
684
+static void __debugfs_file_removed(struct dentry *dentry)
624685 {
625686 	struct debugfs_fsdata *fsd;
626
-
627
-	simple_unlink(d_inode(parent), dentry);
628
-	d_delete(dentry);
629687 
630688 	/*
631689 	 * Paired with the closing smp_mb() implied by a successful
....@@ -641,60 +699,15 @@
641699 		wait_for_completion(&fsd->active_users_drained);
642700 }
643701 
644
-static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
702
+static void remove_one(struct dentry *victim)
645703 {
646
-	int ret = 0;
647
-
648
-	if (simple_positive(dentry)) {
649
-		dget(dentry);
650
-		if (!d_is_reg(dentry)) {
651
-			if (d_is_dir(dentry))
652
-				ret = simple_rmdir(d_inode(parent), dentry);
653
-			else
654
-				simple_unlink(d_inode(parent), dentry);
655
-			if (!ret)
656
-				d_delete(dentry);
657
-		} else {
658
-			__debugfs_remove_file(dentry, parent);
659
-		}
660
-		dput(dentry);
661
-	}
662
-	return ret;
704
+        if (d_is_reg(victim))
705
+		__debugfs_file_removed(victim);
706
+	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
663707 }
664708 
665709 /**
666
- * debugfs_remove - removes a file or directory from the debugfs filesystem
667
- * @dentry: a pointer to a the dentry of the file or directory to be
668
- *          removed.  If this parameter is NULL or an error value, nothing
669
- *          will be done.
670
- *
671
- * This function removes a file or directory in debugfs that was previously
672
- * created with a call to another debugfs function (like
673
- * debugfs_create_file() or variants thereof.)
674
- *
675
- * This function is required to be called in order for the file to be
676
- * removed, no automatic cleanup of files will happen when a module is
677
- * removed, you are responsible here.
678
- */
679
-void debugfs_remove(struct dentry *dentry)
680
-{
681
-	struct dentry *parent;
682
-	int ret;
683
-
684
-	if (IS_ERR_OR_NULL(dentry))
685
-		return;
686
-
687
-	parent = dentry->d_parent;
688
-	inode_lock(d_inode(parent));
689
-	ret = __debugfs_remove(dentry, parent);
690
-	inode_unlock(d_inode(parent));
691
-	if (!ret)
692
-		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
693
-}
694
-EXPORT_SYMBOL_GPL(debugfs_remove);
695
-
696
-/**
697
- * debugfs_remove_recursive - recursively removes a directory
710
+ * debugfs_remove - recursively removes a directory
698711  * @dentry: a pointer to a the dentry of the directory to be removed.  If this
699712  *          parameter is NULL or an error value, nothing will be done.
700713  *
....@@ -706,65 +719,38 @@
706719  * removed, no automatic cleanup of files will happen when a module is
707720  * removed, you are responsible here.
708721  */
709
-void debugfs_remove_recursive(struct dentry *dentry)
722
+void debugfs_remove(struct dentry *dentry)
710723 {
711
-	struct dentry *child, *parent;
712
-
713724 	if (IS_ERR_OR_NULL(dentry))
714725 		return;
715726 
716
-	parent = dentry;
717
- down:
718
-	inode_lock(d_inode(parent));
719
- loop:
720
-	/*
721
-	 * The parent->d_subdirs is protected by the d_lock. Outside that
722
-	 * lock, the child can be unlinked and set to be freed which can
723
-	 * use the d_u.d_child as the rcu head and corrupt this list.
724
-	 */
725
-	spin_lock(&parent->d_lock);
726
-	list_for_each_entry(child, &parent->d_subdirs, d_child) {
727
-		if (!simple_positive(child))
728
-			continue;
729
-
730
-		/* perhaps simple_empty(child) makes more sense */
731
-		if (!list_empty(&child->d_subdirs)) {
732
-			spin_unlock(&parent->d_lock);
733
-			inode_unlock(d_inode(parent));
734
-			parent = child;
735
-			goto down;
736
-		}
737
-
738
-		spin_unlock(&parent->d_lock);
739
-
740
-		if (!__debugfs_remove(child, parent))
741
-			simple_release_fs(&debugfs_mount, &debugfs_mount_count);
742
-
743
-		/*
744
-		 * The parent->d_lock protects agaist child from unlinking
745
-		 * from d_subdirs. When releasing the parent->d_lock we can
746
-		 * no longer trust that the next pointer is valid.
747
-		 * Restart the loop. We'll skip this one with the
748
-		 * simple_positive() check.
749
-		 */
750
-		goto loop;
751
-	}
752
-	spin_unlock(&parent->d_lock);
753
-
754
-	inode_unlock(d_inode(parent));
755
-	child = parent;
756
-	parent = parent->d_parent;
757
-	inode_lock(d_inode(parent));
758
-
759
-	if (child != dentry)
760
-		/* go up */
761
-		goto loop;
762
-
763
-	if (!__debugfs_remove(child, parent))
764
-		simple_release_fs(&debugfs_mount, &debugfs_mount_count);
765
-	inode_unlock(d_inode(parent));
727
+	simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
728
+	simple_recursive_removal(dentry, remove_one);
729
+	simple_release_fs(&debugfs_mount, &debugfs_mount_count);
766730 }
767
-EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
731
+EXPORT_SYMBOL_GPL(debugfs_remove);
732
+
733
+/**
734
+ * debugfs_lookup_and_remove - lookup a directory or file and recursively remove it
735
+ * @name: a pointer to a string containing the name of the item to look up.
736
+ * @parent: a pointer to the parent dentry of the item.
737
+ *
738
+ * This is the equlivant of doing something like
739
+ * debugfs_remove(debugfs_lookup(..)) but with the proper reference counting
740
+ * handled for the directory being looked up.
741
+ */
742
+void debugfs_lookup_and_remove(const char *name, struct dentry *parent)
743
+{
744
+	struct dentry *dentry;
745
+
746
+	dentry = debugfs_lookup(name, parent);
747
+	if (!dentry)
748
+		return;
749
+
750
+	debugfs_remove(dentry);
751
+	dput(dentry);
752
+}
753
+EXPORT_SYMBOL_GPL(debugfs_lookup_and_remove);
768754 
769755 /**
770756  * debugfs_rename - rename a file/directory in the debugfs filesystem
....@@ -821,7 +807,7 @@
821807 		goto exit;
822808 	}
823809 	d_move(old_dentry, dentry);
824
-	fsnotify_move(d_inode(old_dir), d_inode(new_dir), old_name.name,
810
+	fsnotify_move(d_inode(old_dir), d_inode(new_dir), &old_name.name,
825811 		d_is_dir(old_dentry),
826812 		NULL, old_dentry);
827813 	release_dentry_name_snapshot(&old_name);
....@@ -832,7 +818,9 @@
832818 	if (dentry && !IS_ERR(dentry))
833819 		dput(dentry);
834820 	unlock_rename(new_dir, old_dir);
835
-	return NULL;
821
+	if (IS_ERR(dentry))
822
+		return dentry;
823
+	return ERR_PTR(-EINVAL);
836824 }
837825 EXPORT_SYMBOL_GPL(debugfs_rename);
838826 
....@@ -845,9 +833,26 @@
845833 }
846834 EXPORT_SYMBOL_GPL(debugfs_initialized);
847835 
836
+static int __init debugfs_kernel(char *str)
837
+{
838
+	if (str) {
839
+		if (!strcmp(str, "on"))
840
+			debugfs_allow = DEBUGFS_ALLOW_API | DEBUGFS_ALLOW_MOUNT;
841
+		else if (!strcmp(str, "no-mount"))
842
+			debugfs_allow = DEBUGFS_ALLOW_API;
843
+		else if (!strcmp(str, "off"))
844
+			debugfs_allow = 0;
845
+	}
846
+
847
+	return 0;
848
+}
849
+early_param("debugfs", debugfs_kernel);
848850 static int __init debugfs_init(void)
849851 {
850852 	int retval;
853
+
854
+	if (!(debugfs_allow & DEBUGFS_ALLOW_MOUNT))
855
+		return -EPERM;
851856 
852857 	retval = sysfs_create_mount_point(kernel_kobj, "debug");
853858 	if (retval)
....@@ -862,4 +867,3 @@
862867 	return retval;
863868 }
864869 core_initcall(debugfs_init);
865
-