| 1 | |
| 2 | |
| 3 | *
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| 4 | * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
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| 5 | * Written by David Howells ([email protected])
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| 6 |
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| 7 |
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| 8 | #include <linux/fs.h>
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| 9 | #include <linux/cred.h>
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| 10 | #include "internal.h"
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| 11 |
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| 12 | |
| 13 | * determine the security context within which we access the cache from within
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| 14 | * the kernel
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| 15 |
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| 16 | int cachefiles_get_security_ID(struct cachefiles_cache *cache)
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| 17 | {
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| 18 | struct cred *new;
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| 19 | int ret;
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| 20 |
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| 21 | _enter("{%u}", cache->have_secid ? cache->secid : 0);
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| 22 |
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| 23 | new = prepare_kernel_cred(current);
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| 24 | if (!new) {
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| 25 | ret = -ENOMEM;
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| 26 | goto error;
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| 27 | }
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| 28 |
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| 29 | if (cache->have_secid) {
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| 30 | ret = set_security_override(new, cache->secid);
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| 31 | if (ret < 0) {
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| 32 | put_cred(new);
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| 33 | pr_err("Security denies permission to nominate security context: error %d\n",
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| 34 | ret);
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| 35 | goto error;
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| 36 | }
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| 37 | }
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| 38 |
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| 39 | cache->cache_cred = new;
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| 40 | ret = 0;
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| 41 | error:
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| 42 | _leave(" = %d", ret);
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| 43 | return ret;
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| 44 | }
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| 45 |
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| 46 | |
| 47 | * see if mkdir and create can be performed in the root directory
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| 48 |
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| 49 | static int cachefiles_check_cache_dir(struct cachefiles_cache *cache,
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| 50 | struct dentry *root)
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| 51 | {
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| 52 | int ret;
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| 53 |
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| 54 | ret = security_inode_mkdir(d_backing_inode(root), root, 0);
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| 55 | if (ret < 0) {
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| 56 | pr_err("Security denies permission to make dirs: error %d",
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| 57 | ret);
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| 58 | return ret;
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| 59 | }
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| 60 |
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| 61 | ret = security_inode_create(d_backing_inode(root), root, 0);
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| 62 | if (ret < 0)
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| 63 | pr_err("Security denies permission to create files: error %d",
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| 64 | ret);
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| 65 |
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| 66 | return ret;
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| 67 | }
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| 68 |
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| 69 | |
| 70 | * check the security details of the on-disk cache
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| 71 | * - must be called with security override in force
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| 72 | * - must return with a security override in force - even in the case of an
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| 73 | * error
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| 74 |
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| 75 | int cachefiles_determine_cache_security(struct cachefiles_cache *cache,
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| 76 | struct dentry *root,
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| 77 | const struct cred **_saved_cred)
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| 78 | {
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| 79 | struct cred *new;
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| 80 | int ret;
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| 81 |
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| 82 | _enter("");
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| 83 |
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| 84 | |
| 85 | * force, so we can use prepare_creds() to do this)
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| 86 | new = prepare_creds();
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| 87 | if (!new)
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| 88 | return -ENOMEM;
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| 89 |
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| 90 | cachefiles_end_secure(cache, *_saved_cred);
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| 91 |
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| 92 | |
| 93 | * which create files
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| 94 | ret = set_create_files_as(new, d_backing_inode(root));
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| 95 | if (ret < 0) {
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| 96 | abort_creds(new);
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| 97 | cachefiles_begin_secure(cache, _saved_cred);
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| 98 | _leave(" = %d [cfa]", ret);
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| 99 | return ret;
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| 100 | }
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| 101 |
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| 102 | put_cred(cache->cache_cred);
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| 103 | cache->cache_cred = new;
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| 104 |
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| 105 | cachefiles_begin_secure(cache, _saved_cred);
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| 106 | ret = cachefiles_check_cache_dir(cache, root);
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| 107 |
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| 108 | if (ret == -EOPNOTSUPP)
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| 109 | ret = 0;
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| 110 | _leave(" = %d", ret);
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| 111 | return ret;
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| 112 | }
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