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linux-7.2.3/tools/testing/selftests/filesystems/xattr/.gitignore

@@ -0,0 +1,3 @@
+xattr_socket_test
+xattr_sockfs_test
+xattr_socket_types_test

linux-7.2.3/tools/testing/selftests/filesystems/xattr/Makefile

@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+
+CFLAGS += $(KHDR_INCLUDES)
+TEST_GEN_PROGS := xattr_socket_test xattr_sockfs_test xattr_socket_types_test
+
+include ../../lib.mk

linux-7.2.3/tools/testing/selftests/filesystems/xattr/xattr_socket_test.c

@@ -0,0 +1,470 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2026 Christian Brauner <brauner@kernel.org>
+/*
+ * Test extended attributes on path-based Unix domain sockets.
+ *
+ * Path-based Unix domain sockets are bound to a filesystem path and their
+ * inodes live on the underlying filesystem (e.g. tmpfs). These tests verify
+ * that user.* and trusted.* xattr operations work correctly on them using
+ * path-based syscalls (setxattr, getxattr, etc.).
+ *
+ * Covers SOCK_STREAM, SOCK_DGRAM, and SOCK_SEQPACKET socket types.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/xattr.h>
+#include <unistd.h>
+
+#include "../../kselftest_harness.h"
+
+#define TEST_XATTR_NAME		"user.testattr"
+#define TEST_XATTR_VALUE	"testvalue"
+#define TEST_XATTR_VALUE2	"newvalue"
+
+/*
+ * Fixture for path-based Unix domain socket tests.
+ * Creates a SOCK_STREAM socket bound to a path in /tmp (typically tmpfs).
+ */
+FIXTURE(xattr_socket)
+{
+	char socket_path[PATH_MAX];
+	int sockfd;
+};
+
+FIXTURE_VARIANT(xattr_socket)
+{
+	int sock_type;
+	const char *name;
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket, stream) {
+	.sock_type = SOCK_STREAM,
+	.name = "stream",
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket, dgram) {
+	.sock_type = SOCK_DGRAM,
+	.name = "dgram",
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket, seqpacket) {
+	.sock_type = SOCK_SEQPACKET,
+	.name = "seqpacket",
+};
+
+FIXTURE_SETUP(xattr_socket)
+{
+	struct sockaddr_un addr;
+	int ret;
+
+	self->sockfd = -1;
+
+	snprintf(self->socket_path, sizeof(self->socket_path),
+		 "/tmp/xattr_socket_test_%s.%d", variant->name, getpid());
+	unlink(self->socket_path);
+
+	self->sockfd = socket(AF_UNIX, variant->sock_type, 0);
+	ASSERT_GE(self->sockfd, 0) {
+		TH_LOG("Failed to create socket: %s", strerror(errno));
+	}
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+	strncpy(addr.sun_path, self->socket_path, sizeof(addr.sun_path) - 1);
+
+	ret = bind(self->sockfd, (struct sockaddr *)&addr, sizeof(addr));
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("Failed to bind socket to %s: %s",
+		       self->socket_path, strerror(errno));
+	}
+}
+
+FIXTURE_TEARDOWN(xattr_socket)
+{
+	if (self->sockfd >= 0)
+		close(self->sockfd);
+	unlink(self->socket_path);
+}
+
+TEST_F(xattr_socket, set_user_xattr)
+{
+	int ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("setxattr failed: %s (errno=%d)", strerror(errno), errno);
+	}
+}
+
+TEST_F(xattr_socket, get_user_xattr)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("setxattr failed: %s", strerror(errno));
+	}
+
+	memset(buf, 0, sizeof(buf));
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE)) {
+		TH_LOG("getxattr returned %zd, expected %zu: %s",
+		       ret, strlen(TEST_XATTR_VALUE), strerror(errno));
+	}
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+}
+
+TEST_F(xattr_socket, list_user_xattr)
+{
+	char list[1024];
+	ssize_t ret;
+	bool found = false;
+	char *ptr;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("setxattr failed: %s", strerror(errno));
+	}
+
+	memset(list, 0, sizeof(list));
+	ret = listxattr(self->socket_path, list, sizeof(list));
+	ASSERT_GT(ret, 0) {
+		TH_LOG("listxattr failed: %s", strerror(errno));
+	}
+
+	for (ptr = list; ptr < list + ret; ptr += strlen(ptr) + 1) {
+		if (strcmp(ptr, TEST_XATTR_NAME) == 0) {
+			found = true;
+			break;
+		}
+	}
+	ASSERT_TRUE(found) {
+		TH_LOG("xattr %s not found in list", TEST_XATTR_NAME);
+	}
+}
+
+TEST_F(xattr_socket, remove_user_xattr)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("setxattr failed: %s", strerror(errno));
+	}
+
+	ret = removexattr(self->socket_path, TEST_XATTR_NAME);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("removexattr failed: %s", strerror(errno));
+	}
+
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA) {
+		TH_LOG("Expected ENODATA, got %s", strerror(errno));
+	}
+}
+
+/*
+ * Test that xattrs persist across socket close and reopen.
+ * The xattr is on the filesystem inode, not the socket fd.
+ */
+TEST_F(xattr_socket, xattr_persistence)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("setxattr failed: %s", strerror(errno));
+	}
+
+	close(self->sockfd);
+	self->sockfd = -1;
+
+	memset(buf, 0, sizeof(buf));
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE)) {
+		TH_LOG("getxattr after close failed: %s", strerror(errno));
+	}
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+}
+
+TEST_F(xattr_socket, update_user_xattr)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2), 0);
+	ASSERT_EQ(ret, 0);
+
+	memset(buf, 0, sizeof(buf));
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE2));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE2);
+}
+
+TEST_F(xattr_socket, xattr_create_flag)
+{
+	int ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2), XATTR_CREATE);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, EEXIST);
+}
+
+TEST_F(xattr_socket, xattr_replace_flag)
+{
+	int ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), XATTR_REPLACE);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+}
+
+TEST_F(xattr_socket, multiple_xattrs)
+{
+	char buf[256];
+	ssize_t ret;
+	int i;
+	char name[64], value[64];
+	const int num_xattrs = 5;
+
+	for (i = 0; i < num_xattrs; i++) {
+		snprintf(name, sizeof(name), "user.test%d", i);
+		snprintf(value, sizeof(value), "value%d", i);
+		ret = setxattr(self->socket_path, name, value, strlen(value), 0);
+		ASSERT_EQ(ret, 0) {
+			TH_LOG("setxattr %s failed: %s", name, strerror(errno));
+		}
+	}
+
+	for (i = 0; i < num_xattrs; i++) {
+		snprintf(name, sizeof(name), "user.test%d", i);
+		snprintf(value, sizeof(value), "value%d", i);
+		memset(buf, 0, sizeof(buf));
+		ret = getxattr(self->socket_path, name, buf, sizeof(buf));
+		ASSERT_EQ(ret, (ssize_t)strlen(value));
+		ASSERT_STREQ(buf, value);
+	}
+}
+
+TEST_F(xattr_socket, xattr_empty_value)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME, "", 0, 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, 0);
+}
+
+TEST_F(xattr_socket, xattr_get_size)
+{
+	ssize_t ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME, NULL, 0);
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
+}
+
+TEST_F(xattr_socket, xattr_buffer_too_small)
+{
+	char buf[2];
+	ssize_t ret;
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ERANGE);
+}
+
+TEST_F(xattr_socket, xattr_nonexistent)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = getxattr(self->socket_path, "user.nonexistent", buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+}
+
+TEST_F(xattr_socket, remove_nonexistent_xattr)
+{
+	int ret;
+
+	ret = removexattr(self->socket_path, "user.nonexistent");
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+}
+
+TEST_F(xattr_socket, large_xattr_value)
+{
+	char large_value[4096];
+	char read_buf[4096];
+	ssize_t ret;
+
+	memset(large_value, 'A', sizeof(large_value));
+
+	ret = setxattr(self->socket_path, TEST_XATTR_NAME,
+		       large_value, sizeof(large_value), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("setxattr with large value failed: %s", strerror(errno));
+	}
+
+	memset(read_buf, 0, sizeof(read_buf));
+	ret = getxattr(self->socket_path, TEST_XATTR_NAME,
+		       read_buf, sizeof(read_buf));
+	ASSERT_EQ(ret, (ssize_t)sizeof(large_value));
+	ASSERT_EQ(memcmp(large_value, read_buf, sizeof(large_value)), 0);
+}
+
+/*
+ * Test lsetxattr/lgetxattr (don't follow symlinks).
+ * Socket files aren't symlinks, so this should work the same.
+ */
+TEST_F(xattr_socket, lsetxattr_lgetxattr)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = lsetxattr(self->socket_path, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("lsetxattr failed: %s", strerror(errno));
+	}
+
+	memset(buf, 0, sizeof(buf));
+	ret = lgetxattr(self->socket_path, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+}
+
+/*
+ * Fixture for trusted.* xattr tests.
+ * These require CAP_SYS_ADMIN.
+ */
+FIXTURE(xattr_socket_trusted)
+{
+	char socket_path[PATH_MAX];
+	int sockfd;
+};
+
+FIXTURE_VARIANT(xattr_socket_trusted)
+{
+	int sock_type;
+	const char *name;
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket_trusted, stream) {
+	.sock_type = SOCK_STREAM,
+	.name = "stream",
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket_trusted, dgram) {
+	.sock_type = SOCK_DGRAM,
+	.name = "dgram",
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket_trusted, seqpacket) {
+	.sock_type = SOCK_SEQPACKET,
+	.name = "seqpacket",
+};
+
+FIXTURE_SETUP(xattr_socket_trusted)
+{
+	struct sockaddr_un addr;
+	int ret;
+
+	self->sockfd = -1;
+
+	snprintf(self->socket_path, sizeof(self->socket_path),
+		 "/tmp/xattr_socket_trusted_%s.%d", variant->name, getpid());
+	unlink(self->socket_path);
+
+	self->sockfd = socket(AF_UNIX, variant->sock_type, 0);
+	ASSERT_GE(self->sockfd, 0);
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+	strncpy(addr.sun_path, self->socket_path, sizeof(addr.sun_path) - 1);
+
+	ret = bind(self->sockfd, (struct sockaddr *)&addr, sizeof(addr));
+	ASSERT_EQ(ret, 0);
+}
+
+FIXTURE_TEARDOWN(xattr_socket_trusted)
+{
+	if (self->sockfd >= 0)
+		close(self->sockfd);
+	unlink(self->socket_path);
+}
+
+TEST_F(xattr_socket_trusted, set_trusted_xattr)
+{
+	char buf[256];
+	ssize_t len;
+	int ret;
+
+	ret = setxattr(self->socket_path, "trusted.testattr",
+		       TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	if (ret == -1 && errno == EPERM)
+		SKIP(return, "Need CAP_SYS_ADMIN for trusted.* xattrs");
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("setxattr trusted.testattr failed: %s", strerror(errno));
+	}
+
+	memset(buf, 0, sizeof(buf));
+	len = getxattr(self->socket_path, "trusted.testattr",
+		       buf, sizeof(buf));
+	ASSERT_EQ(len, (ssize_t)strlen(TEST_XATTR_VALUE));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+}
+
+TEST_F(xattr_socket_trusted, get_trusted_xattr_unprivileged)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = getxattr(self->socket_path, "trusted.testattr", buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_TRUE(errno == ENODATA || errno == EPERM) {
+		TH_LOG("Expected ENODATA or EPERM, got %s", strerror(errno));
+	}
+}
+
+TEST_HARNESS_MAIN

linux-7.2.3/tools/testing/selftests/filesystems/xattr/xattr_socket_types_test.c

@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2026 Christian Brauner <brauner@kernel.org>
+/*
+ * Test user.* xattrs on various socket families.
+ *
+ * All socket types use sockfs for their inodes, so user.* xattrs should
+ * work on any socket regardless of address family. This tests AF_INET,
+ * AF_INET6, AF_NETLINK, AF_PACKET, and abstract namespace AF_UNIX sockets.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <sys/xattr.h>
+#include <linux/netlink.h>
+#include <unistd.h>
+
+#include "../../kselftest_harness.h"
+
+#define TEST_XATTR_NAME		"user.testattr"
+#define TEST_XATTR_VALUE	"testvalue"
+
+FIXTURE(xattr_socket_types)
+{
+	int sockfd;
+};
+
+FIXTURE_VARIANT(xattr_socket_types)
+{
+	int family;
+	int type;
+	int protocol;
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket_types, inet) {
+	.family = AF_INET,
+	.type = SOCK_STREAM,
+	.protocol = 0,
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket_types, inet6) {
+	.family = AF_INET6,
+	.type = SOCK_STREAM,
+	.protocol = 0,
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket_types, netlink) {
+	.family = AF_NETLINK,
+	.type = SOCK_RAW,
+	.protocol = NETLINK_USERSOCK,
+};
+
+FIXTURE_VARIANT_ADD(xattr_socket_types, packet) {
+	.family = AF_PACKET,
+	.type = SOCK_DGRAM,
+	.protocol = 0,
+};
+
+FIXTURE_SETUP(xattr_socket_types)
+{
+	self->sockfd = socket(variant->family, variant->type,
+			      variant->protocol);
+	if (self->sockfd < 0 &&
+	    (errno == EAFNOSUPPORT || errno == EPERM || errno == EACCES))
+		SKIP(return, "socket(%d, %d, %d) not available: %s",
+		     variant->family, variant->type, variant->protocol,
+		     strerror(errno));
+	ASSERT_GE(self->sockfd, 0) {
+		TH_LOG("Failed to create socket(%d, %d, %d): %s",
+		       variant->family, variant->type, variant->protocol,
+		       strerror(errno));
+	}
+}
+
+FIXTURE_TEARDOWN(xattr_socket_types)
+{
+	if (self->sockfd >= 0)
+		close(self->sockfd);
+}
+
+TEST_F(xattr_socket_types, set_get_list_remove)
+{
+	char buf[256], list[4096], *ptr;
+	ssize_t ret;
+	bool found;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("fsetxattr failed: %s", strerror(errno));
+	}
+
+	memset(buf, 0, sizeof(buf));
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+
+	memset(list, 0, sizeof(list));
+	ret = flistxattr(self->sockfd, list, sizeof(list));
+	ASSERT_GT(ret, 0);
+	found = false;
+	for (ptr = list; ptr < list + ret; ptr += strlen(ptr) + 1) {
+		if (strcmp(ptr, TEST_XATTR_NAME) == 0)
+			found = true;
+	}
+	ASSERT_TRUE(found);
+
+	ret = fremovexattr(self->sockfd, TEST_XATTR_NAME);
+	ASSERT_EQ(ret, 0);
+
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+}
+
+/*
+ * Test abstract namespace AF_UNIX socket.
+ * Abstract sockets don't have a filesystem path; their inodes live in
+ * sockfs so user.* xattrs should work via fsetxattr/fgetxattr.
+ */
+FIXTURE(xattr_abstract)
+{
+	int sockfd;
+};
+
+FIXTURE_SETUP(xattr_abstract)
+{
+	struct sockaddr_un addr;
+	char name[64];
+	int ret, len;
+
+	self->sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_GE(self->sockfd, 0);
+
+	len = snprintf(name, sizeof(name), "xattr_test_abstract_%d", getpid());
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sun_family = AF_UNIX;
+	addr.sun_path[0] = '\0';
+	memcpy(&addr.sun_path[1], name, len);
+
+	ret = bind(self->sockfd, (struct sockaddr *)&addr,
+		   offsetof(struct sockaddr_un, sun_path) + 1 + len);
+	ASSERT_EQ(ret, 0);
+}
+
+FIXTURE_TEARDOWN(xattr_abstract)
+{
+	if (self->sockfd >= 0)
+		close(self->sockfd);
+}
+
+TEST_F(xattr_abstract, set_get)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("fsetxattr on abstract socket failed: %s",
+		       strerror(errno));
+	}
+
+	memset(buf, 0, sizeof(buf));
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+}
+
+TEST_HARNESS_MAIN

linux-7.2.3/tools/testing/selftests/filesystems/xattr/xattr_sockfs_test.c

@@ -0,0 +1,363 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2026 Christian Brauner <brauner@kernel.org>
+/*
+ * Test extended attributes on sockfs sockets.
+ *
+ * Sockets created via socket() have their inodes in sockfs, which supports
+ * user.* xattrs with per-inode limits: up to 128 xattrs and 128KB total
+ * value size. These tests verify xattr operations via fsetxattr/fgetxattr/
+ * flistxattr/fremovexattr on the socket fd, as well as limit enforcement.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/xattr.h>
+#include <unistd.h>
+
+#include "../../kselftest_harness.h"
+
+#define TEST_XATTR_NAME		"user.testattr"
+#define TEST_XATTR_VALUE	"testvalue"
+#define TEST_XATTR_VALUE2	"newvalue"
+
+/* Per-inode limits for user.* xattrs on sockfs (from include/linux/xattr.h) */
+#define SIMPLE_XATTR_MAX_NR	128
+#define SIMPLE_XATTR_MAX_SIZE	(128 << 10)	/* 128 KB */
+
+#ifndef XATTR_SIZE_MAX
+#define XATTR_SIZE_MAX 65536
+#endif
+
+/*
+ * Fixture for sockfs socket xattr tests.
+ * Creates an AF_UNIX socket (lives in sockfs, not bound to any path).
+ */
+FIXTURE(xattr_sockfs)
+{
+	int sockfd;
+};
+
+FIXTURE_SETUP(xattr_sockfs)
+{
+	self->sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_GE(self->sockfd, 0) {
+		TH_LOG("Failed to create socket: %s", strerror(errno));
+	}
+}
+
+FIXTURE_TEARDOWN(xattr_sockfs)
+{
+	if (self->sockfd >= 0)
+		close(self->sockfd);
+}
+
+TEST_F(xattr_sockfs, set_get_user_xattr)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("fsetxattr failed: %s", strerror(errno));
+	}
+
+	memset(buf, 0, sizeof(buf));
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE)) {
+		TH_LOG("fgetxattr returned %zd: %s", ret, strerror(errno));
+	}
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+}
+
+/*
+ * Test listing xattrs on a sockfs socket.
+ * Should include user.* xattrs and system.sockprotoname.
+ */
+TEST_F(xattr_sockfs, list_user_xattr)
+{
+	char list[4096];
+	ssize_t ret;
+	char *ptr;
+	bool found_user = false;
+	bool found_proto = false;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("fsetxattr failed: %s", strerror(errno));
+	}
+
+	memset(list, 0, sizeof(list));
+	ret = flistxattr(self->sockfd, list, sizeof(list));
+	ASSERT_GT(ret, 0) {
+		TH_LOG("flistxattr failed: %s", strerror(errno));
+	}
+
+	for (ptr = list; ptr < list + ret; ptr += strlen(ptr) + 1) {
+		if (strcmp(ptr, TEST_XATTR_NAME) == 0)
+			found_user = true;
+		if (strcmp(ptr, "system.sockprotoname") == 0)
+			found_proto = true;
+	}
+	ASSERT_TRUE(found_user) {
+		TH_LOG("user xattr not found in list");
+	}
+	ASSERT_TRUE(found_proto) {
+		TH_LOG("system.sockprotoname not found in list");
+	}
+}
+
+TEST_F(xattr_sockfs, remove_user_xattr)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = fremovexattr(self->sockfd, TEST_XATTR_NAME);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("fremovexattr failed: %s", strerror(errno));
+	}
+
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+}
+
+TEST_F(xattr_sockfs, update_user_xattr)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2), 0);
+	ASSERT_EQ(ret, 0);
+
+	memset(buf, 0, sizeof(buf));
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE2));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE2);
+}
+
+TEST_F(xattr_sockfs, xattr_create_flag)
+{
+	int ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2),
+			XATTR_CREATE);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, EEXIST);
+}
+
+TEST_F(xattr_sockfs, xattr_replace_flag)
+{
+	int ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE),
+			XATTR_REPLACE);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+}
+
+TEST_F(xattr_sockfs, get_nonexistent)
+{
+	char buf[256];
+	ssize_t ret;
+
+	ret = fgetxattr(self->sockfd, "user.nonexistent", buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+}
+
+TEST_F(xattr_sockfs, empty_value)
+{
+	ssize_t ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME, "", 0, 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, NULL, 0);
+	ASSERT_EQ(ret, 0);
+}
+
+TEST_F(xattr_sockfs, get_size)
+{
+	ssize_t ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, NULL, 0);
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
+}
+
+TEST_F(xattr_sockfs, buffer_too_small)
+{
+	char buf[2];
+	ssize_t ret;
+
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ERANGE);
+}
+
+/*
+ * Test maximum number of user.* xattrs per socket.
+ * The kernel enforces SIMPLE_XATTR_MAX_NR (128), so the 129th should
+ * fail with ENOSPC.
+ */
+TEST_F(xattr_sockfs, max_nr_xattrs)
+{
+	char name[32];
+	int i, ret;
+
+	for (i = 0; i < SIMPLE_XATTR_MAX_NR; i++) {
+		snprintf(name, sizeof(name), "user.test%03d", i);
+		ret = fsetxattr(self->sockfd, name, "v", 1, 0);
+		ASSERT_EQ(ret, 0) {
+			TH_LOG("fsetxattr %s failed at i=%d: %s",
+			       name, i, strerror(errno));
+		}
+	}
+
+	ret = fsetxattr(self->sockfd, "user.overflow", "v", 1, 0);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENOSPC) {
+		TH_LOG("Expected ENOSPC for xattr %d, got %s",
+		       SIMPLE_XATTR_MAX_NR + 1, strerror(errno));
+	}
+}
+
+/*
+ * Test maximum total value size for user.* xattrs.
+ * The kernel enforces SIMPLE_XATTR_MAX_SIZE (128KB). Individual xattr
+ * values are limited to XATTR_SIZE_MAX (64KB) by the VFS, so we need
+ * at least two xattrs to hit the total limit.
+ */
+TEST_F(xattr_sockfs, max_xattr_size)
+{
+	char *value;
+	int ret;
+
+	value = malloc(XATTR_SIZE_MAX);
+	ASSERT_NE(value, NULL);
+	memset(value, 'A', XATTR_SIZE_MAX);
+
+	/* First 64KB xattr - total = 64KB */
+	ret = fsetxattr(self->sockfd, "user.big1", value, XATTR_SIZE_MAX, 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("first large xattr failed: %s", strerror(errno));
+	}
+
+	/* Second 64KB xattr - total = 128KB (exactly at limit) */
+	ret = fsetxattr(self->sockfd, "user.big2", value, XATTR_SIZE_MAX, 0);
+	free(value);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("second large xattr failed: %s", strerror(errno));
+	}
+
+	/* Third xattr with 1 byte - total > 128KB, should fail */
+	ret = fsetxattr(self->sockfd, "user.big3", "v", 1, 0);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENOSPC) {
+		TH_LOG("Expected ENOSPC when exceeding size limit, got %s",
+		       strerror(errno));
+	}
+}
+
+/*
+ * Test that removing an xattr frees limit space, allowing re-addition.
+ */
+TEST_F(xattr_sockfs, limit_remove_readd)
+{
+	char name[32];
+	int i, ret;
+
+	/* Fill up to the maximum count */
+	for (i = 0; i < SIMPLE_XATTR_MAX_NR; i++) {
+		snprintf(name, sizeof(name), "user.test%03d", i);
+		ret = fsetxattr(self->sockfd, name, "v", 1, 0);
+		ASSERT_EQ(ret, 0);
+	}
+
+	/* Verify we're at the limit */
+	ret = fsetxattr(self->sockfd, "user.overflow", "v", 1, 0);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENOSPC);
+
+	/* Remove one xattr */
+	ret = fremovexattr(self->sockfd, "user.test000");
+	ASSERT_EQ(ret, 0);
+
+	/* Now we should be able to add one more */
+	ret = fsetxattr(self->sockfd, "user.newattr", "v", 1, 0);
+	ASSERT_EQ(ret, 0) {
+		TH_LOG("re-add after remove failed: %s", strerror(errno));
+	}
+}
+
+/*
+ * Test that two different sockets have independent xattr limits.
+ */
+TEST_F(xattr_sockfs, limits_per_inode)
+{
+	char buf[256];
+	int sock2;
+	ssize_t ret;
+
+	sock2 = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_GE(sock2, 0);
+
+	/* Set xattr on first socket */
+	ret = fsetxattr(self->sockfd, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE, strlen(TEST_XATTR_VALUE), 0);
+	ASSERT_EQ(ret, 0);
+
+	/* First socket's xattr should not be visible on second socket */
+	ret = fgetxattr(sock2, TEST_XATTR_NAME, NULL, 0);
+	ASSERT_EQ(ret, -1);
+	ASSERT_EQ(errno, ENODATA);
+
+	/* Second socket should independently accept xattrs */
+	ret = fsetxattr(sock2, TEST_XATTR_NAME,
+			TEST_XATTR_VALUE2, strlen(TEST_XATTR_VALUE2), 0);
+	ASSERT_EQ(ret, 0);
+
+	/* Verify each socket has its own value */
+	memset(buf, 0, sizeof(buf));
+	ret = fgetxattr(self->sockfd, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE);
+
+	memset(buf, 0, sizeof(buf));
+	ret = fgetxattr(sock2, TEST_XATTR_NAME, buf, sizeof(buf));
+	ASSERT_EQ(ret, (ssize_t)strlen(TEST_XATTR_VALUE2));
+	ASSERT_STREQ(buf, TEST_XATTR_VALUE2);
+
+	close(sock2);
+}
+
+TEST_HARNESS_MAIN