Re: [PATCH 13/14] selftests/xattr: sockfs socket xattr tests

[Jan Kara <jack@suse.cz>]

On Mon 16-02-26 14:32:09, Christian Brauner wrote:
> Test user.* extended attribute operations on sockfs sockets. Sockets
> created via socket() have their inodes in sockfs, which now supports
> user.* xattrs with per-inode limits.
> 
> Tests fsetxattr/fgetxattr/flistxattr/fremovexattr operations including
> set/get, listing (verifies system.sockprotoname presence), remove,
> update, XATTR_CREATE/XATTR_REPLACE flags, empty values, size queries,
> and buffer-too-small errors.
> 
> Also tests per-inode limit enforcement: maximum 128 xattrs, maximum
> 128KB total value size, limit recovery after removal, and independent
> limits across different sockets.
> 
> Signed-off-by: Christian Brauner <brauner@kernel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  .../testing/selftests/filesystems/xattr/.gitignore |   1 +
>  tools/testing/selftests/filesystems/xattr/Makefile |   2 +-
>  .../filesystems/xattr/xattr_sockfs_test.c          | 363 +++++++++++++++++++++
>  3 files changed, 365 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/filesystems/xattr/.gitignore b/tools/testing/selftests/filesystems/xattr/.gitignore
> index 5fd015d2257a..00a59c89efab 100644
> --- a/tools/testing/selftests/filesystems/xattr/.gitignore
> +++ b/tools/testing/selftests/filesystems/xattr/.gitignore
> @@ -1 +1,2 @@
>  xattr_socket_test
> +xattr_sockfs_test
> diff --git a/tools/testing/selftests/filesystems/xattr/Makefile b/tools/testing/selftests/filesystems/xattr/Makefile
> index e3d8dca80faa..2cd722dba47b 100644
> --- a/tools/testing/selftests/filesystems/xattr/Makefile
> +++ b/tools/testing/selftests/filesystems/xattr/Makefile
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  
>  CFLAGS += $(KHDR_INCLUDES)
> -TEST_GEN_PROGS := xattr_socket_test
> +TEST_GEN_PROGS := xattr_socket_test xattr_sockfs_test
>  
>  include ../../lib.mk
> diff --git a/tools/testing/selftests/filesystems/xattr/xattr_sockfs_test.c b/tools/testing/selftests/filesystems/xattr/xattr_sockfs_test.c
> new file mode 100644
> index 000000000000..b4824b01a86d
> --- /dev/null
> +++ b/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
> 
> -- 
> 2.47.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR