Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2// Copyright (c) 2026 Christian Brauner <brauner@kernel.org>
3/*
4 * Test extended attributes on sockfs sockets.
5 *
6 * Sockets created via socket() have their inodes in sockfs, which supports
7 * user.* xattrs with per-inode limits: up to 128 xattrs and 128KB total
8 * value size. These tests verify xattr operations via fsetxattr/fgetxattr/
9 * flistxattr/fremovexattr on the socket fd, as well as limit enforcement.
10 */
11
12#define _GNU_SOURCE
13#include <errno.h>
14#include <stdio.h>
15#include <stdlib.h>
16#include <string.h>
17#include <sys/socket.h>
18#include <sys/types.h>
19#include <sys/xattr.h>
20#include <unistd.h>
21
22#include "../../kselftest_harness.h"
23
24#define TEST_XATTR_NAME "user.testattr"
25#define TEST_XATTR_VALUE "testvalue"
26#define TEST_XATTR_VALUE2 "newvalue"
27
28/* Per-inode limits for user.* xattrs on sockfs (from include/linux/xattr.h) */
29#define SIMPLE_XATTR_MAX_NR 128
30#define SIMPLE_XATTR_MAX_SIZE (128 << 10) /* 128 KB */
31
32#ifndef XATTR_SIZE_MAX
33#define XATTR_SIZE_MAX 65536
34#endif
35
36/*
37 * Fixture for sockfs socket xattr tests.
38 * Creates an AF_UNIX socket (lives in sockfs, not bound to any path).
39 */
40FIXTURE(xattr_sockfs)
41{
42 int sockfd;
43};
44
45FIXTURE_SETUP(xattr_sockfs)
46{
47 self->sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
48 ASSERT_GE(self->sockfd, 0) {
49 TH_LOG("Failed to create socket: %s", strerror(errno));
50 }
51}
52
53FIXTURE_TEARDOWN(xattr_sockfs)
54{
55 if (self->sockfd >= 0)
56 close(self->sockfd);
57}
58
59TEST_F(xattr_sockfs, set_get_user_xattr)
60{
61 char buf[256];
62 ssize_t ret;
63
64 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
65 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
66 ASSERT_EQ(ret, 0) {
67 TH_LOG("fsetxattr failed: %s", strerror(errno));
68 }
69
70 memset(buf, 0, sizeof(buf));
71 ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
72 ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE)) {
73 TH_LOG("fgetxattr returned %zd: %s", ret, strerror(errno));
74 }
75 ASSERT_STREQ(buf, TEST_XATTR_VALUE);
76}
77
78/*
79 * Test listing xattrs on a sockfs socket.
80 * Should include user.* xattrs and system.sockprotoname.
81 */
82TEST_F(xattr_sockfs, list_user_xattr)
83{
84 char list[4096];
85 ssize_t ret;
86 char *ptr;
87 bool found_user = false;
88 bool found_proto = false;
89
90 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
91 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
92 ASSERT_EQ(ret, 0) {
93 TH_LOG("fsetxattr failed: %s", strerror(errno));
94 }
95
96 memset(list, 0, sizeof(list));
97 ret = flistxattr(self->sockfd, list, sizeof(list));
98 ASSERT_GT(ret, 0) {
99 TH_LOG("flistxattr failed: %s", strerror(errno));
100 }
101
102 for (ptr = list; ptr < list + ret; ptr += strlen(ptr) + 1) {
103 if (strcmp(ptr, TEST_XATTR_NAME) == 0)
104 found_user = true;
105 if (strcmp(ptr, "system.sockprotoname") == 0)
106 found_proto = true;
107 }
108 ASSERT_TRUE(found_user) {
109 TH_LOG("user xattr not found in list");
110 }
111 ASSERT_TRUE(found_proto) {
112 TH_LOG("system.sockprotoname not found in list");
113 }
114}
115
116TEST_F(xattr_sockfs, remove_user_xattr)
117{
118 char buf[256];
119 ssize_t ret;
120
121 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
122 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
123 ASSERT_EQ(ret, 0);
124
125 ret = fremovexattr(self->sockfd, TEST_XATTR_NAME);
126 ASSERT_EQ(ret, 0) {
127 TH_LOG("fremovexattr failed: %s", strerror(errno));
128 }
129
130 ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
131 ASSERT_EQ(ret, -1);
132 ASSERT_EQ(errno, ENODATA);
133}
134
135TEST_F(xattr_sockfs, update_user_xattr)
136{
137 char buf[256];
138 ssize_t ret;
139
140 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
141 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
142 ASSERT_EQ(ret, 0);
143
144 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
145 TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2), 0);
146 ASSERT_EQ(ret, 0);
147
148 memset(buf, 0, sizeof(buf));
149 ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
150 ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE2));
151 ASSERT_STREQ(buf, TEST_XATTR_VALUE2);
152}
153
154TEST_F(xattr_sockfs, xattr_create_flag)
155{
156 int ret;
157
158 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
159 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
160 ASSERT_EQ(ret, 0);
161
162 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
163 TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2),
164 XATTR_CREATE);
165 ASSERT_EQ(ret, -1);
166 ASSERT_EQ(errno, EEXIST);
167}
168
169TEST_F(xattr_sockfs, xattr_replace_flag)
170{
171 int ret;
172
173 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
174 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE),
175 XATTR_REPLACE);
176 ASSERT_EQ(ret, -1);
177 ASSERT_EQ(errno, ENODATA);
178}
179
180TEST_F(xattr_sockfs, get_nonexistent)
181{
182 char buf[256];
183 ssize_t ret;
184
185 ret = fgetxattr(self->sockfd, "user.nonexistent", buf, sizeof(buf));
186 ASSERT_EQ(ret, -1);
187 ASSERT_EQ(errno, ENODATA);
188}
189
190TEST_F(xattr_sockfs, empty_value)
191{
192 ssize_t ret;
193
194 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME, "", 0, 0);
195 ASSERT_EQ(ret, 0);
196
197 ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, NULL, 0);
198 ASSERT_EQ(ret, 0);
199}
200
201TEST_F(xattr_sockfs, get_size)
202{
203 ssize_t ret;
204
205 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
206 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
207 ASSERT_EQ(ret, 0);
208
209 ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, NULL, 0);
210 ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
211}
212
213TEST_F(xattr_sockfs, buffer_too_small)
214{
215 char buf[2];
216 ssize_t ret;
217
218 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
219 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
220 ASSERT_EQ(ret, 0);
221
222 ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
223 ASSERT_EQ(ret, -1);
224 ASSERT_EQ(errno, ERANGE);
225}
226
227/*
228 * Test maximum number of user.* xattrs per socket.
229 * The kernel enforces SIMPLE_XATTR_MAX_NR (128), so the 129th should
230 * fail with ENOSPC.
231 */
232TEST_F(xattr_sockfs, max_nr_xattrs)
233{
234 char name[32];
235 int i, ret;
236
237 for (i = 0; i < SIMPLE_XATTR_MAX_NR; i++) {
238 snprintf(name, sizeof(name), "user.test%03d", i);
239 ret = fsetxattr(self->sockfd, name, "v", 1, 0);
240 ASSERT_EQ(ret, 0) {
241 TH_LOG("fsetxattr %s failed at i=%d: %s",
242 name, i, strerror(errno));
243 }
244 }
245
246 ret = fsetxattr(self->sockfd, "user.overflow", "v", 1, 0);
247 ASSERT_EQ(ret, -1);
248 ASSERT_EQ(errno, ENOSPC) {
249 TH_LOG("Expected ENOSPC for xattr %d, got %s",
250 SIMPLE_XATTR_MAX_NR + 1, strerror(errno));
251 }
252}
253
254/*
255 * Test maximum total value size for user.* xattrs.
256 * The kernel enforces SIMPLE_XATTR_MAX_SIZE (128KB). Individual xattr
257 * values are limited to XATTR_SIZE_MAX (64KB) by the VFS, so we need
258 * at least two xattrs to hit the total limit.
259 */
260TEST_F(xattr_sockfs, max_xattr_size)
261{
262 char *value;
263 int ret;
264
265 value = malloc(XATTR_SIZE_MAX);
266 ASSERT_NE(value, NULL);
267 memset(value, 'A', XATTR_SIZE_MAX);
268
269 /* First 64KB xattr - total = 64KB */
270 ret = fsetxattr(self->sockfd, "user.big1", value, XATTR_SIZE_MAX, 0);
271 ASSERT_EQ(ret, 0) {
272 TH_LOG("first large xattr failed: %s", strerror(errno));
273 }
274
275 /* Second 64KB xattr - total = 128KB (exactly at limit) */
276 ret = fsetxattr(self->sockfd, "user.big2", value, XATTR_SIZE_MAX, 0);
277 free(value);
278 ASSERT_EQ(ret, 0) {
279 TH_LOG("second large xattr failed: %s", strerror(errno));
280 }
281
282 /* Third xattr with 1 byte - total > 128KB, should fail */
283 ret = fsetxattr(self->sockfd, "user.big3", "v", 1, 0);
284 ASSERT_EQ(ret, -1);
285 ASSERT_EQ(errno, ENOSPC) {
286 TH_LOG("Expected ENOSPC when exceeding size limit, got %s",
287 strerror(errno));
288 }
289}
290
291/*
292 * Test that removing an xattr frees limit space, allowing re-addition.
293 */
294TEST_F(xattr_sockfs, limit_remove_readd)
295{
296 char name[32];
297 int i, ret;
298
299 /* Fill up to the maximum count */
300 for (i = 0; i < SIMPLE_XATTR_MAX_NR; i++) {
301 snprintf(name, sizeof(name), "user.test%03d", i);
302 ret = fsetxattr(self->sockfd, name, "v", 1, 0);
303 ASSERT_EQ(ret, 0);
304 }
305
306 /* Verify we're at the limit */
307 ret = fsetxattr(self->sockfd, "user.overflow", "v", 1, 0);
308 ASSERT_EQ(ret, -1);
309 ASSERT_EQ(errno, ENOSPC);
310
311 /* Remove one xattr */
312 ret = fremovexattr(self->sockfd, "user.test000");
313 ASSERT_EQ(ret, 0);
314
315 /* Now we should be able to add one more */
316 ret = fsetxattr(self->sockfd, "user.newattr", "v", 1, 0);
317 ASSERT_EQ(ret, 0) {
318 TH_LOG("re-add after remove failed: %s", strerror(errno));
319 }
320}
321
322/*
323 * Test that two different sockets have independent xattr limits.
324 */
325TEST_F(xattr_sockfs, limits_per_inode)
326{
327 char buf[256];
328 int sock2;
329 ssize_t ret;
330
331 sock2 = socket(AF_UNIX, SOCK_STREAM, 0);
332 ASSERT_GE(sock2, 0);
333
334 /* Set xattr on first socket */
335 ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
336 TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
337 ASSERT_EQ(ret, 0);
338
339 /* First socket's xattr should not be visible on second socket */
340 ret = fgetxattr(sock2, TEST_XATTR_NAME, NULL, 0);
341 ASSERT_EQ(ret, -1);
342 ASSERT_EQ(errno, ENODATA);
343
344 /* Second socket should independently accept xattrs */
345 ret = fsetxattr(sock2, TEST_XATTR_NAME,
346 TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2), 0);
347 ASSERT_EQ(ret, 0);
348
349 /* Verify each socket has its own value */
350 memset(buf, 0, sizeof(buf));
351 ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
352 ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
353 ASSERT_STREQ(buf, TEST_XATTR_VALUE);
354
355 memset(buf, 0, sizeof(buf));
356 ret = fgetxattr(sock2, TEST_XATTR_NAME, buf, sizeof(buf));
357 ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE2));
358 ASSERT_STREQ(buf, TEST_XATTR_VALUE2);
359
360 close(sock2);
361}
362
363TEST_HARNESS_MAIN