1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
3
4 #include <vmlinux.h>
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_tracing.h>
7 #include <bpf/bpf_core_read.h>
8 #include "bpf_misc.h"
9 #include "xdp_metadata.h"
10 #include "bpf_kfuncs.h"
11
12 extern struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym __weak;
13 extern void bpf_task_release(struct task_struct *p) __ksym __weak;
14
15 __weak int subprog_trusted_task_nullable(struct task_struct *task __arg_trusted __arg_nullable)
16 {
17 if (!task)
18 return 0;
19 return task->pid + task->tgid;
20 }
21
22 __weak int subprog_trusted_task_nullable_extra_layer(struct task_struct *task __arg_trusted __arg_nullable)
23 {
24 return subprog_trusted_task_nullable(task) + subprog_trusted_task_nullable(NULL);
25 }
26
27 SEC("?tp_btf/task_newtask")
28 __success __log_level(2)
29 __msg("Validating subprog_trusted_task_nullable() func#1...")
30 __msg(": R1=trusted_ptr_or_null_task_struct(")
31 int trusted_task_arg_nullable(void *ctx)
32 {
33 struct task_struct *t1 = bpf_get_current_task_btf();
34 struct task_struct *t2 = bpf_task_acquire(t1);
35 int res = 0;
36
37 /* known NULL */
38 res += subprog_trusted_task_nullable(NULL);
39
40 /* known non-NULL */
41 res += subprog_trusted_task_nullable(t1);
42 res += subprog_trusted_task_nullable_extra_layer(t1);
43
44 /* unknown if NULL or not */
45 res += subprog_trusted_task_nullable(t2);
46 res += subprog_trusted_task_nullable_extra_layer(t2);
47
48 if (t2) {
49 /* known non-NULL after explicit NULL check, just in case */
50 res += subprog_trusted_task_nullable(t2);
51 res += subprog_trusted_task_nullable_extra_layer(t2);
52
53 bpf_task_release(t2);
54 }
55
56 return res;
57 }
58
59 __weak int subprog_trusted_task_nonnull(struct task_struct *task __arg_trusted)
60 {
61 return task->pid + task->tgid;
62 }
63
64 SEC("?kprobe")
65 __failure __log_level(2)
66 __msg("R1 type=scalar expected=ptr_, trusted_ptr_, rcu_ptr_")
67 __msg("Caller passes invalid args into func#1 ('subprog_trusted_task_nonnull')")
68 int trusted_task_arg_nonnull_fail1(void *ctx)
69 {
70 return subprog_trusted_task_nonnull(NULL);
71 }
72
73 SEC("?tp_btf/task_newtask")
74 __failure __log_level(2)
75 __msg("R1 type=ptr_or_null_ expected=ptr_, trusted_ptr_, rcu_ptr_")
76 __msg("Caller passes invalid args into func#1 ('subprog_trusted_task_nonnull')")
77 int trusted_task_arg_nonnull_fail2(void *ctx)
78 {
79 struct task_struct *t = bpf_get_current_task_btf();
80 struct task_struct *nullable;
81 int res;
82
83 nullable = bpf_task_acquire(t);
84
85 /* should fail, PTR_TO_BTF_ID_OR_NULL */
86 res = subprog_trusted_task_nonnull(nullable);
87
88 if (nullable)
89 bpf_task_release(nullable);
90
91 return res;
92 }
93
94 SEC("?kprobe")
95 __success __log_level(2)
96 __msg("Validating subprog_trusted_task_nonnull() func#1...")
97 __msg(": R1=trusted_ptr_task_struct(")
98 int trusted_task_arg_nonnull(void *ctx)
99 {
100 struct task_struct *t = bpf_get_current_task_btf();
101
102 return subprog_trusted_task_nonnull(t);
103 }
104
105 struct task_struct___local {} __attribute__((preserve_access_index));
106
107 __weak int subprog_nullable_task_flavor(
108 struct task_struct___local *task __arg_trusted __arg_nullable)
109 {
110 char buf[16];
111
112 if (!task)
113 return 0;
114
115 return bpf_copy_from_user_task(&buf, sizeof(buf), NULL, (void *)task, 0);
116 }
117
118 SEC("?uprobe.s")
119 __success __log_level(2)
120 __msg("Validating subprog_nullable_task_flavor() func#1...")
121 __msg(": R1=trusted_ptr_or_null_task_struct(")
122 int flavor_ptr_nullable(void *ctx)
123 {
124 struct task_struct___local *t = (void *)bpf_get_current_task_btf();
125
126 return subprog_nullable_task_flavor(t);
127 }
128
129 __weak int subprog_nonnull_task_flavor(struct task_struct___local *task __arg_trusted)
130 {
131 char buf[16];
132
133 return bpf_copy_from_user_task(&buf, sizeof(buf), NULL, (void *)task, 0);
134 }
135
136 SEC("?uprobe.s")
137 __success __log_level(2)
138 __msg("Validating subprog_nonnull_task_flavor() func#1...")
139 __msg(": R1=trusted_ptr_task_struct(")
140 int flavor_ptr_nonnull(void *ctx)
141 {
142 struct task_struct *t = bpf_get_current_task_btf();
143
144 return subprog_nonnull_task_flavor((void *)t);
145 }
146
147 __weak int subprog_trusted_destroy(struct task_struct *task __arg_trusted)
148 {
149 bpf_task_release(task); /* should be rejected */
150
151 return 0;
152 }
153
154 SEC("?tp_btf/task_newtask")
155 __failure __log_level(2)
156 __msg("release kernel function bpf_task_release expects refcounted PTR_TO_BTF_ID")
157 int BPF_PROG(trusted_destroy_fail, struct task_struct *task, u64 clone_flags)
158 {
159 return subprog_trusted_destroy(task);
160 }
161
162 __weak int subprog_trusted_acq_rel(struct task_struct *task __arg_trusted)
163 {
164 struct task_struct *owned;
165
166 owned = bpf_task_acquire(task);
167 if (!owned)
168 return 0;
169
170 bpf_task_release(owned); /* this one is OK, we acquired it locally */
171
172 return 0;
173 }
174
175 SEC("?tp_btf/task_newtask")
176 __success __log_level(2)
177 int BPF_PROG(trusted_acq_rel, struct task_struct *task, u64 clone_flags)
178 {
179 return subprog_trusted_acq_rel(task);
180 }
181
182 char _license[] SEC("license") = "GPL";
183
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