Re: [PATCH 12/14] selftests/xattr: path-based AF_UNIX socket xattr tests

[Jan Kara]

On Mon 16-02-26 14:32:08, Christian Brauner wrote:
> Test user.* extended attribute operations on path-based Unix domain
> sockets (SOCK_STREAM, SOCK_DGRAM, SOCK_SEQPACKET). Path-based sockets
> are bound to a filesystem path and their inodes live on the underlying
> filesystem (e.g. tmpfs).
> 
> Covers set/get/list/remove, persistence, XATTR_CREATE/XATTR_REPLACE
> flags, empty values, size queries, buffer-too-small errors, O_PATH fd
> operations, and trusted.* xattr handling.
> 
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  .../testing/selftests/filesystems/xattr/.gitignore |   1 +
>  tools/testing/selftests/filesystems/xattr/Makefile |   6 +
>  .../filesystems/xattr/xattr_socket_test.c          | 470 +++++++++++++++++++++
>  3 files changed, 477 insertions(+)
> 
> diff --git a/tools/testing/selftests/filesystems/xattr/.gitignore b/tools/testing/selftests/filesystems/xattr/.gitignore
> new file mode 100644
> index 000000000000..5fd015d2257a
> --- /dev/null
> +++ b/tools/testing/selftests/filesystems/xattr/.gitignore
> @@ -0,0 +1 @@
> +xattr_socket_test
> diff --git a/tools/testing/selftests/filesystems/xattr/Makefile b/tools/testing/selftests/filesystems/xattr/Makefile
> new file mode 100644
> index 000000000000..e3d8dca80faa
> --- /dev/null
> +++ b/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
> +
> +include ../../lib.mk
> diff --git a/tools/testing/selftests/filesystems/xattr/xattr_socket_test.c b/tools/testing/selftests/filesystems/xattr/xattr_socket_test.c
> new file mode 100644
> index 000000000000..fac0a4c6bc05
> --- /dev/null
> +++ b/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@xxxxxxxxxx>
> +/*
> + * 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
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR