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2024-10-09 244b2c5ca8b14627e4a17755e5922221e121c771 
 kernel/kernel/bpf/inode.c
....@@ -1,3 +1,4 @@
1
+// SPDX-License-Identifier: GPL-2.0-only
12 /*
23  * Minimal file system backend for holding eBPF maps and programs,
34  * used by bpf(2) object pinning.
....@@ -5,10 +6,6 @@
56  * Authors:
67  *
78  *	Daniel Borkmann <daniel@iogearbox.net>
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
11
- * version 2 as published by the Free Software Foundation.
129  */
1310 
1411 #include <linux/init.h>
....@@ -17,26 +14,32 @@
1714 #include <linux/mount.h>
1815 #include <linux/namei.h>
1916 #include <linux/fs.h>
17
+#include <linux/fs_context.h>
18
+#include <linux/fs_parser.h>
2019 #include <linux/kdev_t.h>
21
-#include <linux/parser.h>
2220 #include <linux/filter.h>
2321 #include <linux/bpf.h>
2422 #include <linux/bpf_trace.h>
23
+#include "preload/bpf_preload.h"
2524 
2625 enum bpf_type {
2726 	BPF_TYPE_UNSPEC	= 0,
2827 	BPF_TYPE_PROG,
2928 	BPF_TYPE_MAP,
29
+	BPF_TYPE_LINK,
3030 };
3131 
3232 static void *bpf_any_get(void *raw, enum bpf_type type)
3333 {
3434 	switch (type) {
3535 	case BPF_TYPE_PROG:
36
-		raw = bpf_prog_inc(raw);
36
+		bpf_prog_inc(raw);
3737 		break;
3838 	case BPF_TYPE_MAP:
39
-		raw = bpf_map_inc(raw, true);
39
+		bpf_map_inc_with_uref(raw);
40
+		break;
41
+	case BPF_TYPE_LINK:
42
+		bpf_link_inc(raw);
4043 		break;
4144 	default:
4245 		WARN_ON_ONCE(1);
....@@ -55,6 +58,9 @@
5558 	case BPF_TYPE_MAP:
5659 		bpf_map_put_with_uref(raw);
5760 		break;
61
+	case BPF_TYPE_LINK:
62
+		bpf_link_put(raw);
63
+		break;
5864 	default:
5965 		WARN_ON_ONCE(1);
6066 		break;
....@@ -65,20 +71,32 @@
6571 {
6672 	void *raw;
6773 
68
-	*type = BPF_TYPE_MAP;
6974 	raw = bpf_map_get_with_uref(ufd);
70
-	if (IS_ERR(raw)) {
71
-		*type = BPF_TYPE_PROG;
72
-		raw = bpf_prog_get(ufd);
75
+	if (!IS_ERR(raw)) {
76
+		*type = BPF_TYPE_MAP;
77
+		return raw;
7378 	}
7479 
75
-	return raw;
80
+	raw = bpf_prog_get(ufd);
81
+	if (!IS_ERR(raw)) {
82
+		*type = BPF_TYPE_PROG;
83
+		return raw;
84
+	}
85
+
86
+	raw = bpf_link_get_from_fd(ufd);
87
+	if (!IS_ERR(raw)) {
88
+		*type = BPF_TYPE_LINK;
89
+		return raw;
90
+	}
91
+
92
+	return ERR_PTR(-EINVAL);
7693 }
7794 
7895 static const struct inode_operations bpf_dir_iops;
7996 
8097 static const struct inode_operations bpf_prog_iops = { };
8198 static const struct inode_operations bpf_map_iops  = { };
99
+static const struct inode_operations bpf_link_iops  = { };
82100 
83101 static struct inode *bpf_get_inode(struct super_block *sb,
84102 				   const struct inode *dir,
....@@ -116,6 +134,8 @@
116134 		*type = BPF_TYPE_PROG;
117135 	else if (inode->i_op == &bpf_map_iops)
118136 		*type = BPF_TYPE_MAP;
137
+	else if (inode->i_op == &bpf_link_iops)
138
+		*type = BPF_TYPE_LINK;
119139 	else
120140 		return -EACCES;
121141 
....@@ -339,13 +359,23 @@
339359 			     &bpffs_map_fops : &bpffs_obj_fops);
340360 }
341361 
362
+static int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg)
363
+{
364
+	struct bpf_link *link = arg;
365
+
366
+	return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops,
367
+			     bpf_link_is_iter(link) ?
368
+			     &bpf_iter_fops : &bpffs_obj_fops);
369
+}
370
+
342371 static struct dentry *
343372 bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
344373 {
345374 	/* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future
346
-	 * extensions.
375
+	 * extensions. That allows popoulate_bpffs() create special files.
347376 	 */
348
-	if (strchr(dentry->d_name.name, '.'))
377
+	if ((dir->i_mode & S_IALLUGO) &&
378
+	    strchr(dentry->d_name.name, '.'))
349379 		return ERR_PTR(-EPERM);
350380 
351381 	return simple_lookup(dir, dentry, flags);
....@@ -383,7 +413,28 @@
383413 	.unlink		= simple_unlink,
384414 };
385415 
386
-static int bpf_obj_do_pin(const struct filename *pathname, void *raw,
416
+/* pin iterator link into bpffs */
417
+static int bpf_iter_link_pin_kernel(struct dentry *parent,
418
+				    const char *name, struct bpf_link *link)
419
+{
420
+	umode_t mode = S_IFREG | S_IRUSR;
421
+	struct dentry *dentry;
422
+	int ret;
423
+
424
+	inode_lock(parent->d_inode);
425
+	dentry = lookup_one_len(name, parent, strlen(name));
426
+	if (IS_ERR(dentry)) {
427
+		inode_unlock(parent->d_inode);
428
+		return PTR_ERR(dentry);
429
+	}
430
+	ret = bpf_mkobj_ops(dentry, mode, link, &bpf_link_iops,
431
+			    &bpf_iter_fops);
432
+	dput(dentry);
433
+	inode_unlock(parent->d_inode);
434
+	return ret;
435
+}
436
+
437
+static int bpf_obj_do_pin(const char __user *pathname, void *raw,
387438 			  enum bpf_type type)
388439 {
389440 	struct dentry *dentry;
....@@ -392,7 +443,7 @@
392443 	umode_t mode;
393444 	int ret;
394445 
395
-	dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0);
446
+	dentry = user_path_create(AT_FDCWD, pathname, &path, 0);
396447 	if (IS_ERR(dentry))
397448 		return PTR_ERR(dentry);
398449 
....@@ -415,6 +466,9 @@
415466 	case BPF_TYPE_MAP:
416467 		ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw);
417468 		break;
469
+	case BPF_TYPE_LINK:
470
+		ret = vfs_mkobj(dentry, mode, bpf_mklink, raw);
471
+		break;
418472 	default:
419473 		ret = -EPERM;
420474 	}
....@@ -425,30 +479,22 @@
425479 
426480 int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
427481 {
428
-	struct filename *pname;
429482 	enum bpf_type type;
430483 	void *raw;
431484 	int ret;
432485 
433
-	pname = getname(pathname);
434
-	if (IS_ERR(pname))
435
-		return PTR_ERR(pname);
436
-
437486 	raw = bpf_fd_probe_obj(ufd, &type);
438
-	if (IS_ERR(raw)) {
439
-		ret = PTR_ERR(raw);
440
-		goto out;
441
-	}
487
+	if (IS_ERR(raw))
488
+		return PTR_ERR(raw);
442489 
443
-	ret = bpf_obj_do_pin(pname, raw, type);
490
+	ret = bpf_obj_do_pin(pathname, raw, type);
444491 	if (ret != 0)
445492 		bpf_any_put(raw, type);
446
-out:
447
-	putname(pname);
493
+
448494 	return ret;
449495 }
450496 
451
-static void *bpf_obj_do_get(const struct filename *pathname,
497
+static void *bpf_obj_do_get(const char __user *pathname,
452498 			    enum bpf_type *type, int flags)
453499 {
454500 	struct inode *inode;
....@@ -456,7 +502,7 @@
456502 	void *raw;
457503 	int ret;
458504 
459
-	ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path);
505
+	ret = user_path_at(AT_FDCWD, pathname, LOOKUP_FOLLOW, &path);
460506 	if (ret)
461507 		return ERR_PTR(ret);
462508 
....@@ -483,36 +529,29 @@
483529 int bpf_obj_get_user(const char __user *pathname, int flags)
484530 {
485531 	enum bpf_type type = BPF_TYPE_UNSPEC;
486
-	struct filename *pname;
487
-	int ret = -ENOENT;
488532 	int f_flags;
489533 	void *raw;
534
+	int ret;
490535 
491536 	f_flags = bpf_get_file_flag(flags);
492537 	if (f_flags < 0)
493538 		return f_flags;
494539 
495
-	pname = getname(pathname);
496
-	if (IS_ERR(pname))
497
-		return PTR_ERR(pname);
498
-
499
-	raw = bpf_obj_do_get(pname, &type, f_flags);
500
-	if (IS_ERR(raw)) {
501
-		ret = PTR_ERR(raw);
502
-		goto out;
503
-	}
540
+	raw = bpf_obj_do_get(pathname, &type, f_flags);
541
+	if (IS_ERR(raw))
542
+		return PTR_ERR(raw);
504543 
505544 	if (type == BPF_TYPE_PROG)
506545 		ret = bpf_prog_new_fd(raw);
507546 	else if (type == BPF_TYPE_MAP)
508547 		ret = bpf_map_new_fd(raw, f_flags);
548
+	else if (type == BPF_TYPE_LINK)
549
+		ret = (f_flags != O_RDWR) ? -EINVAL : bpf_link_new_fd(raw);
509550 	else
510
-		goto out;
551
+		return -ENOENT;
511552 
512553 	if (ret < 0)
513554 		bpf_any_put(raw, type);
514
-out:
515
-	putname(pname);
516555 	return ret;
517556 }
518557 
....@@ -524,6 +563,8 @@
524563 		return ERR_PTR(ret);
525564 
526565 	if (inode->i_op == &bpf_map_iops)
566
+		return ERR_PTR(-EINVAL);
567
+	if (inode->i_op == &bpf_link_iops)
527568 		return ERR_PTR(-EINVAL);
528569 	if (inode->i_op != &bpf_prog_iops)
529570 		return ERR_PTR(-EACCES);
....@@ -537,7 +578,8 @@
537578 	if (!bpf_prog_get_ok(prog, &type, false))
538579 		return ERR_PTR(-EINVAL);
539580 
540
-	return bpf_prog_inc(prog);
581
+	bpf_prog_inc(prog);
582
+	return prog;
541583 }
542584 
543585 struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)
....@@ -567,9 +609,8 @@
567609 	return 0;
568610 }
569611 
570
-static void bpf_destroy_inode_deferred(struct rcu_head *head)
612
+static void bpf_free_inode(struct inode *inode)
571613 {
572
-	struct inode *inode = container_of(head, struct inode, i_rcu);
573614 	enum bpf_type type;
574615 
575616 	if (S_ISLNK(inode->i_mode))
....@@ -579,71 +620,140 @@
579620 	free_inode_nonrcu(inode);
580621 }
581622 
582
-static void bpf_destroy_inode(struct inode *inode)
583
-{
584
-	call_rcu(&inode->i_rcu, bpf_destroy_inode_deferred);
585
-}
586
-
587623 static const struct super_operations bpf_super_ops = {
588624 	.statfs		= simple_statfs,
589625 	.drop_inode	= generic_delete_inode,
590626 	.show_options	= bpf_show_options,
591
-	.destroy_inode	= bpf_destroy_inode,
627
+	.free_inode	= bpf_free_inode,
592628 };
593629 
594630 enum {
595631 	OPT_MODE,
596
-	OPT_ERR,
597632 };
598633 
599
-static const match_table_t bpf_mount_tokens = {
600
-	{ OPT_MODE, "mode=%o" },
601
-	{ OPT_ERR, NULL },
634
+static const struct fs_parameter_spec bpf_fs_parameters[] = {
635
+	fsparam_u32oct	("mode",			OPT_MODE),
636
+	{}
602637 };
603638 
604639 struct bpf_mount_opts {
605640 	umode_t mode;
606641 };
607642 
608
-static int bpf_parse_options(char *data, struct bpf_mount_opts *opts)
643
+static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param)
609644 {
610
-	substring_t args[MAX_OPT_ARGS];
611
-	int option, token;
612
-	char *ptr;
645
+	struct bpf_mount_opts *opts = fc->fs_private;
646
+	struct fs_parse_result result;
647
+	int opt;
613648 
614
-	opts->mode = S_IRWXUGO;
615
-
616
-	while ((ptr = strsep(&data, ",")) != NULL) {
617
-		if (!*ptr)
618
-			continue;
619
-
620
-		token = match_token(ptr, bpf_mount_tokens, args);
621
-		switch (token) {
622
-		case OPT_MODE:
623
-			if (match_octal(&args[0], &option))
624
-				return -EINVAL;
625
-			opts->mode = option & S_IALLUGO;
626
-			break;
649
+	opt = fs_parse(fc, bpf_fs_parameters, param, &result);
650
+	if (opt < 0)
627651 		/* We might like to report bad mount options here, but
628652 		 * traditionally we've ignored all mount options, so we'd
629653 		 * better continue to ignore non-existing options for bpf.
630654 		 */
631
-		}
655
+		return opt == -ENOPARAM ? 0 : opt;
656
+
657
+	switch (opt) {
658
+	case OPT_MODE:
659
+		opts->mode = result.uint_32 & S_IALLUGO;
660
+		break;
632661 	}
633662 
634663 	return 0;
635664 }
636665 
637
-static int bpf_fill_super(struct super_block *sb, void *data, int silent)
666
+struct bpf_preload_ops *bpf_preload_ops;
667
+EXPORT_SYMBOL_GPL(bpf_preload_ops);
668
+
669
+static bool bpf_preload_mod_get(void)
670
+{
671
+	/* If bpf_preload.ko wasn't loaded earlier then load it now.
672
+	 * When bpf_preload is built into vmlinux the module's __init
673
+	 * function will populate it.
674
+	 */
675
+	if (!bpf_preload_ops) {
676
+		request_module("bpf_preload");
677
+		if (!bpf_preload_ops)
678
+			return false;
679
+	}
680
+	/* And grab the reference, so the module doesn't disappear while the
681
+	 * kernel is interacting with the kernel module and its UMD.
682
+	 */
683
+	if (!try_module_get(bpf_preload_ops->owner)) {
684
+		pr_err("bpf_preload module get failed.\n");
685
+		return false;
686
+	}
687
+	return true;
688
+}
689
+
690
+static void bpf_preload_mod_put(void)
691
+{
692
+	if (bpf_preload_ops)
693
+		/* now user can "rmmod bpf_preload" if necessary */
694
+		module_put(bpf_preload_ops->owner);
695
+}
696
+
697
+static DEFINE_MUTEX(bpf_preload_lock);
698
+
699
+static int populate_bpffs(struct dentry *parent)
700
+{
701
+	struct bpf_preload_info objs[BPF_PRELOAD_LINKS] = {};
702
+	struct bpf_link *links[BPF_PRELOAD_LINKS] = {};
703
+	int err = 0, i;
704
+
705
+	/* grab the mutex to make sure the kernel interactions with bpf_preload
706
+	 * UMD are serialized
707
+	 */
708
+	mutex_lock(&bpf_preload_lock);
709
+
710
+	/* if bpf_preload.ko wasn't built into vmlinux then load it */
711
+	if (!bpf_preload_mod_get())
712
+		goto out;
713
+
714
+	if (!bpf_preload_ops->info.tgid) {
715
+		/* preload() will start UMD that will load BPF iterator programs */
716
+		err = bpf_preload_ops->preload(objs);
717
+		if (err)
718
+			goto out_put;
719
+		for (i = 0; i < BPF_PRELOAD_LINKS; i++) {
720
+			links[i] = bpf_link_by_id(objs[i].link_id);
721
+			if (IS_ERR(links[i])) {
722
+				err = PTR_ERR(links[i]);
723
+				goto out_put;
724
+			}
725
+		}
726
+		for (i = 0; i < BPF_PRELOAD_LINKS; i++) {
727
+			err = bpf_iter_link_pin_kernel(parent,
728
+						       objs[i].link_name, links[i]);
729
+			if (err)
730
+				goto out_put;
731
+			/* do not unlink successfully pinned links even
732
+			 * if later link fails to pin
733
+			 */
734
+			links[i] = NULL;
735
+		}
736
+		/* finish() will tell UMD process to exit */
737
+		err = bpf_preload_ops->finish();
738
+		if (err)
739
+			goto out_put;
740
+	}
741
+out_put:
742
+	bpf_preload_mod_put();
743
+out:
744
+	mutex_unlock(&bpf_preload_lock);
745
+	for (i = 0; i < BPF_PRELOAD_LINKS && err; i++)
746
+		if (!IS_ERR_OR_NULL(links[i]))
747
+			bpf_link_put(links[i]);
748
+	return err;
749
+}
750
+
751
+static int bpf_fill_super(struct super_block *sb, struct fs_context *fc)
638752 {
639753 	static const struct tree_descr bpf_rfiles[] = { { "" } };
640
-	struct bpf_mount_opts opts;
754
+	struct bpf_mount_opts *opts = fc->fs_private;
641755 	struct inode *inode;
642756 	int ret;
643
-
644
-	ret = bpf_parse_options(data, &opts);
645
-	if (ret)
646
-		return ret;
647757 
648758 	ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);
649759 	if (ret)
....@@ -654,21 +764,50 @@
654764 	inode = sb->s_root->d_inode;
655765 	inode->i_op = &bpf_dir_iops;
656766 	inode->i_mode &= ~S_IALLUGO;
657
-	inode->i_mode |= S_ISVTX | opts.mode;
658
-
767
+	populate_bpffs(sb->s_root);
768
+	inode->i_mode |= S_ISVTX | opts->mode;
659769 	return 0;
660770 }
661771 
662
-static struct dentry *bpf_mount(struct file_system_type *type, int flags,
663
-				const char *dev_name, void *data)
772
+static int bpf_get_tree(struct fs_context *fc)
664773 {
665
-	return mount_nodev(type, flags, data, bpf_fill_super);
774
+	return get_tree_nodev(fc, bpf_fill_super);
775
+}
776
+
777
+static void bpf_free_fc(struct fs_context *fc)
778
+{
779
+	kfree(fc->fs_private);
780
+}
781
+
782
+static const struct fs_context_operations bpf_context_ops = {
783
+	.free		= bpf_free_fc,
784
+	.parse_param	= bpf_parse_param,
785
+	.get_tree	= bpf_get_tree,
786
+};
787
+
788
+/*
789
+ * Set up the filesystem mount context.
790
+ */
791
+static int bpf_init_fs_context(struct fs_context *fc)
792
+{
793
+	struct bpf_mount_opts *opts;
794
+
795
+	opts = kzalloc(sizeof(struct bpf_mount_opts), GFP_KERNEL);
796
+	if (!opts)
797
+		return -ENOMEM;
798
+
799
+	opts->mode = S_IRWXUGO;
800
+
801
+	fc->fs_private = opts;
802
+	fc->ops = &bpf_context_ops;
803
+	return 0;
666804 }
667805 
668806 static struct file_system_type bpf_fs_type = {
669807 	.owner		= THIS_MODULE,
670808 	.name		= "bpf",
671
-	.mount		= bpf_mount,
809
+	.init_fs_context = bpf_init_fs_context,
810
+	.parameters	= bpf_fs_parameters,
672811 	.kill_sb	= kill_litter_super,
673812 };
674813 
....@@ -676,6 +815,8 @@
676815 {
677816 	int ret;
678817 
818
+	mutex_init(&bpf_preload_lock);
819
+
679820 	ret = sysfs_create_mount_point(fs_kobj, "bpf");
680821 	if (ret)
681822 		return ret;