Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'bpf-classify-block-device-hooks-and-add-selftests'
Christian Brauner says:
====================
bpf: classify block device hooks and add selftests
A bunch of new hooks for managing block devices were added a while ago
but they weren't appropriately classified. Classify them and add a test
program so we catch regressions.
Note that for whatever reason building the bpf selftests locally seems
to fail for all kinds of arcane reasons for me. That might just be my
fault. I added a pr against the ci to have the selftests run but to test
this meaningfully it needs veritysetup and dmverity support. I'm not
sure if that's available already.
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
Changes in v2:
- No changes.
- Link to v1: https://patch.msgid.link/20260220-work-bpf-bdev-v1-0-c53e852c4702@kernel.org
---
====================
Link: https://patch.msgid.link/20260326-work-bpf-bdev-v2-0-5e3c58963987@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
+321
+4
kernel/bpf/bpf_lsm.c
+4
kernel/bpf/bpf_lsm.c
···
383
383
BTF_ID(func, bpf_lsm_task_setscheduler)
384
384
BTF_ID(func, bpf_lsm_task_to_inode)
385
385
BTF_ID(func, bpf_lsm_userns_create)
386
+
BTF_ID(func, bpf_lsm_bdev_alloc)
387
+
BTF_ID(func, bpf_lsm_bdev_setintegrity)
386
388
BTF_SET_END(sleepable_lsm_hooks)
387
389
388
390
BTF_SET_START(untrusted_lsm_hooks)
···
397
395
BTF_ID(func, bpf_lsm_sk_free_security)
398
396
#endif /* CONFIG_SECURITY_NETWORK */
399
397
BTF_ID(func, bpf_lsm_task_free)
398
+
BTF_ID(func, bpf_lsm_bdev_alloc)
399
+
BTF_ID(func, bpf_lsm_bdev_free)
400
400
BTF_SET_END(untrusted_lsm_hooks)
401
401
402
402
bool bpf_lsm_is_sleepable_hook(u32 btf_id)
+221
tools/testing/selftests/bpf/prog_tests/lsm_bdev.c
+221
tools/testing/selftests/bpf/prog_tests/lsm_bdev.c
···
1
+
// SPDX-License-Identifier: GPL-2.0
2
+
/* Copyright (c) 2026 Christian Brauner <brauner@kernel.org> */
3
+
4
+
/*
5
+
* Test BPF LSM block device integrity hooks with dm-verity.
6
+
*
7
+
* Creates a dm-verity device over loopback, which triggers
8
+
* security_bdev_setintegrity() during verity_preresume().
9
+
* Verifies that the BPF program correctly tracks the integrity
10
+
* metadata in its hashmap.
11
+
*/
12
+
13
+
#define _GNU_SOURCE
14
+
#include <test_progs.h>
15
+
#include <fcntl.h>
16
+
#include <stdio.h>
17
+
#include <stdlib.h>
18
+
#include <string.h>
19
+
#include <sys/stat.h>
20
+
#include <sys/types.h>
21
+
#include <unistd.h>
22
+
#include "lsm_bdev.skel.h"
23
+
24
+
/* Must match the definition in progs/lsm_bdev.c. */
25
+
struct verity_info {
26
+
__u8 has_roothash;
27
+
__u8 sig_valid;
28
+
__u32 setintegrity_cnt;
29
+
};
30
+
31
+
#define DATA_SIZE_MB 8
32
+
#define HASH_SIZE_MB 1
33
+
#define DM_NAME "bpf_test_verity"
34
+
#define DM_DEV_PATH "/dev/mapper/" DM_NAME
35
+
36
+
/* Run a command and optionally capture the first line of stdout. */
37
+
static int run_cmd(const char *cmd, char *out, size_t out_sz)
38
+
{
39
+
FILE *fp;
40
+
int ret;
41
+
42
+
fp = popen(cmd, "r");
43
+
if (!fp)
44
+
return -1;
45
+
46
+
if (out && out_sz > 0) {
47
+
if (!fgets(out, out_sz, fp))
48
+
out[0] = '\0';
49
+
/* strip trailing newline */
50
+
out[strcspn(out, "\n")] = '\0';
51
+
}
52
+
53
+
ret = pclose(fp);
54
+
return WIFEXITED(ret) ? WEXITSTATUS(ret) : -1;
55
+
}
56
+
57
+
static bool has_prerequisites(void)
58
+
{
59
+
if (getuid() != 0) {
60
+
printf("SKIP: must be root\n");
61
+
return false;
62
+
}
63
+
64
+
if (run_cmd("modprobe loop 2>/dev/null", NULL, 0) &&
65
+
run_cmd("ls /dev/loop-control 2>/dev/null", NULL, 0)) {
66
+
printf("SKIP: no loop device support\n");
67
+
return false;
68
+
}
69
+
70
+
if (run_cmd("modprobe dm-verity 2>/dev/null", NULL, 0) &&
71
+
run_cmd("dmsetup targets 2>/dev/null | grep -q verity", NULL, 0)) {
72
+
printf("SKIP: dm-verity module not available\n");
73
+
return false;
74
+
}
75
+
76
+
if (run_cmd("which veritysetup >/dev/null 2>&1", NULL, 0)) {
77
+
printf("SKIP: veritysetup not found\n");
78
+
return false;
79
+
}
80
+
81
+
return true;
82
+
}
83
+
84
+
void test_lsm_bdev(void)
85
+
{
86
+
char data_img[] = "/tmp/bpf_verity_data_XXXXXX";
87
+
char hash_img[] = "/tmp/bpf_verity_hash_XXXXXX";
88
+
char data_loop[64] = {};
89
+
char hash_loop[64] = {};
90
+
char roothash[256] = {};
91
+
char cmd[512];
92
+
int data_fd = -1, hash_fd = -1;
93
+
struct lsm_bdev *skel = NULL;
94
+
struct verity_info val;
95
+
struct stat st;
96
+
__u32 dev_key;
97
+
int err;
98
+
99
+
if (!has_prerequisites()) {
100
+
test__skip();
101
+
return;
102
+
}
103
+
104
+
/* Clean up any stale device from a previous crashed run. */
105
+
snprintf(cmd, sizeof(cmd), "dmsetup remove %s 2>/dev/null", DM_NAME);
106
+
run_cmd(cmd, NULL, 0);
107
+
108
+
/* Create temporary image files. */
109
+
data_fd = mkstemp(data_img);
110
+
if (!ASSERT_OK_FD(data_fd, "mkstemp data"))
111
+
return;
112
+
113
+
hash_fd = mkstemp(hash_img);
114
+
if (!ASSERT_OK_FD(hash_fd, "mkstemp hash"))
115
+
goto cleanup;
116
+
117
+
if (!ASSERT_OK(ftruncate(data_fd, DATA_SIZE_MB * 1024 * 1024),
118
+
"truncate data"))
119
+
goto cleanup;
120
+
121
+
if (!ASSERT_OK(ftruncate(hash_fd, HASH_SIZE_MB * 1024 * 1024),
122
+
"truncate hash"))
123
+
goto cleanup;
124
+
125
+
close(data_fd);
126
+
data_fd = -1;
127
+
close(hash_fd);
128
+
hash_fd = -1;
129
+
130
+
/* Set up loop devices. */
131
+
snprintf(cmd, sizeof(cmd),
132
+
"losetup --find --show %s 2>/dev/null", data_img);
133
+
if (!ASSERT_OK(run_cmd(cmd, data_loop, sizeof(data_loop)),
134
+
"losetup data"))
135
+
goto teardown;
136
+
137
+
snprintf(cmd, sizeof(cmd),
138
+
"losetup --find --show %s 2>/dev/null", hash_img);
139
+
if (!ASSERT_OK(run_cmd(cmd, hash_loop, sizeof(hash_loop)),
140
+
"losetup hash"))
141
+
goto teardown;
142
+
143
+
/* Format the dm-verity device and capture the root hash. */
144
+
snprintf(cmd, sizeof(cmd),
145
+
"veritysetup format %s %s 2>/dev/null | "
146
+
"grep -i 'root hash' | awk '{print $NF}'",
147
+
data_loop, hash_loop);
148
+
if (!ASSERT_OK(run_cmd(cmd, roothash, sizeof(roothash)),
149
+
"veritysetup format"))
150
+
goto teardown;
151
+
152
+
if (!ASSERT_GT((int)strlen(roothash), 0, "roothash not empty"))
153
+
goto teardown;
154
+
155
+
/* Load and attach BPF program before activating dm-verity. */
156
+
skel = lsm_bdev__open_and_load();
157
+
if (!ASSERT_OK_PTR(skel, "skel open_and_load"))
158
+
goto teardown;
159
+
160
+
err = lsm_bdev__attach(skel);
161
+
if (!ASSERT_OK(err, "skel attach"))
162
+
goto teardown;
163
+
164
+
/* Activate dm-verity — triggers verity_preresume() hooks. */
165
+
snprintf(cmd, sizeof(cmd),
166
+
"veritysetup open %s %s %s %s 2>/dev/null",
167
+
data_loop, DM_NAME, hash_loop, roothash);
168
+
if (!ASSERT_OK(run_cmd(cmd, NULL, 0), "veritysetup open"))
169
+
goto teardown;
170
+
171
+
/* Get the dm device's dev_t. */
172
+
if (!ASSERT_OK(stat(DM_DEV_PATH, &st), "stat dm dev"))
173
+
goto remove_dm;
174
+
175
+
dev_key = (__u32)st.st_rdev;
176
+
177
+
/* Look up the device in the BPF map and verify. */
178
+
err = bpf_map__lookup_elem(skel->maps.verity_devices,
179
+
&dev_key, sizeof(dev_key),
180
+
&val, sizeof(val), 0);
181
+
if (!ASSERT_OK(err, "map lookup"))
182
+
goto remove_dm;
183
+
184
+
ASSERT_EQ(val.has_roothash, 1, "has_roothash");
185
+
ASSERT_EQ(val.sig_valid, 0, "sig_valid (unsigned)");
186
+
/*
187
+
* verity_preresume() always calls security_bdev_setintegrity()
188
+
* for the roothash. The signature-validity call only happens
189
+
* when CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG is enabled.
190
+
*/
191
+
ASSERT_GE(val.setintegrity_cnt, 1, "setintegrity_cnt min");
192
+
ASSERT_LE(val.setintegrity_cnt, 2, "setintegrity_cnt max");
193
+
194
+
/* Verify that the alloc hook fired at least once. */
195
+
ASSERT_GT(skel->bss->alloc_count, 0, "alloc_count");
196
+
197
+
remove_dm:
198
+
snprintf(cmd, sizeof(cmd), "dmsetup remove %s 2>/dev/null", DM_NAME);
199
+
run_cmd(cmd, NULL, 0);
200
+
201
+
teardown:
202
+
if (data_loop[0]) {
203
+
snprintf(cmd, sizeof(cmd), "losetup -d %s 2>/dev/null",
204
+
data_loop);
205
+
run_cmd(cmd, NULL, 0);
206
+
}
207
+
if (hash_loop[0]) {
208
+
snprintf(cmd, sizeof(cmd), "losetup -d %s 2>/dev/null",
209
+
hash_loop);
210
+
run_cmd(cmd, NULL, 0);
211
+
}
212
+
213
+
cleanup:
214
+
lsm_bdev__destroy(skel);
215
+
if (data_fd >= 0)
216
+
close(data_fd);
217
+
if (hash_fd >= 0)
218
+
close(hash_fd);
219
+
unlink(data_img);
220
+
unlink(hash_img);
221
+
}
+96
tools/testing/selftests/bpf/progs/lsm_bdev.c
+96
tools/testing/selftests/bpf/progs/lsm_bdev.c
···
1
+
// SPDX-License-Identifier: GPL-2.0
2
+
/* Copyright (c) 2026 Christian Brauner <brauner@kernel.org> */
3
+
4
+
/*
5
+
* BPF LSM block device integrity tracker for dm-verity.
6
+
*
7
+
* Tracks block devices in a hashmap keyed by bd_dev. When dm-verity
8
+
* calls security_bdev_setintegrity() during verity_preresume(), the
9
+
* setintegrity hook records the roothash and signature-validity data.
10
+
* The free hook cleans up when the device goes away. The alloc hook
11
+
* counts allocations for test validation.
12
+
*
13
+
* The sleepable hooks exercise bpf_copy_from_user() to verify that
14
+
* the sleepable classification actually permits sleepable helpers.
15
+
*/
16
+
17
+
#include "vmlinux.h"
18
+
#include <bpf/bpf_helpers.h>
19
+
#include <bpf/bpf_tracing.h>
20
+
21
+
struct verity_info {
22
+
__u8 has_roothash; /* LSM_INT_DMVERITY_ROOTHASH seen */
23
+
__u8 sig_valid; /* LSM_INT_DMVERITY_SIG_VALID value (non-NULL = valid) */
24
+
__u32 setintegrity_cnt; /* total setintegrity calls for this dev */
25
+
};
26
+
27
+
struct {
28
+
__uint(type, BPF_MAP_TYPE_HASH);
29
+
__uint(max_entries, 64);
30
+
__type(key, __u32); /* dev_t from bdev->bd_dev */
31
+
__type(value, struct verity_info);
32
+
} verity_devices SEC(".maps");
33
+
34
+
/* Global counters exposed to userspace via skeleton bss. */
35
+
int alloc_count;
36
+
37
+
char _license[] SEC("license") = "GPL";
38
+
39
+
SEC("lsm.s/bdev_setintegrity")
40
+
int BPF_PROG(bdev_setintegrity, struct block_device *bdev,
41
+
enum lsm_integrity_type type, const void *value, size_t size)
42
+
{
43
+
struct verity_info zero = {};
44
+
struct verity_info *info;
45
+
__u32 dev;
46
+
char buf;
47
+
48
+
/*
49
+
* Exercise a sleepable helper to confirm the verifier
50
+
* allows it in this sleepable hook.
51
+
*/
52
+
(void)bpf_copy_from_user(&buf, sizeof(buf), NULL);
53
+
54
+
dev = bdev->bd_dev;
55
+
56
+
info = bpf_map_lookup_elem(&verity_devices, &dev);
57
+
if (!info) {
58
+
bpf_map_update_elem(&verity_devices, &dev, &zero, BPF_NOEXIST);
59
+
info = bpf_map_lookup_elem(&verity_devices, &dev);
60
+
if (!info)
61
+
return 0;
62
+
}
63
+
64
+
if (type == LSM_INT_DMVERITY_ROOTHASH)
65
+
info->has_roothash = 1;
66
+
else if (type == LSM_INT_DMVERITY_SIG_VALID)
67
+
info->sig_valid = (value != NULL);
68
+
69
+
__sync_fetch_and_add(&info->setintegrity_cnt, 1);
70
+
71
+
return 0;
72
+
}
73
+
74
+
SEC("lsm/bdev_free_security")
75
+
void BPF_PROG(bdev_free_security, struct block_device *bdev)
76
+
{
77
+
__u32 dev = bdev->bd_dev;
78
+
79
+
bpf_map_delete_elem(&verity_devices, &dev);
80
+
}
81
+
82
+
SEC("lsm.s/bdev_alloc_security")
83
+
int BPF_PROG(bdev_alloc_security, struct block_device *bdev)
84
+
{
85
+
char buf;
86
+
87
+
/*
88
+
* Exercise a sleepable helper to confirm the verifier
89
+
* allows it in this sleepable hook.
90
+
*/
91
+
(void)bpf_copy_from_user(&buf, sizeof(buf), NULL);
92
+
93
+
__sync_fetch_and_add(&alloc_count, 1);
94
+
95
+
return 0;
96
+
}