io_uring_chcon.c

/*
 * io_uring_chcon.c
 *
 * Copyright (C) 2021 Giuseppe Scrivano <giuseppe@scrivano.org>
 * io_uring_chcon is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * io_uring_chcon is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with crun.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <fcntl.h>
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/xattr.h>
#include <unistd.h>
#include <dirent.h>
#include <liburing.h>

#define XATTR_NAME "security.selinux"
#define QUEUE_DEPTH 4096

struct context_s {
	struct io_uring *ring;

	const char *value;
	size_t value_len;

	size_t infly;
	size_t reqs;
};

static int do_submit_queue(struct context_s *ctx)
{
	int r;

	r = io_uring_submit(ctx->ring);
	if (r < 0) {
		fprintf(stderr, "io_uring_submit: %m\n");
		return r;
	}

	return 0;
}

static inline int handle_completion(struct context_s *ctx, struct io_uring_cqe *cqe)
{
	char *name;
	int res;
	ctx->infly--;

	name = io_uring_cqe_get_data(cqe);
	res = cqe->res;
	if (res < 0) {
		errno = -res;
		fprintf(stderr, "setxattr (%s): %m\n", name);
	}
	io_uring_cqe_seen(ctx->ring, cqe);

	free(name);

	return res;
}

static int do_peek(struct context_s *ctx)
{
	struct io_uring_cqe *cqe;
	int r;

	/* Cleanup as many entries as possible.  */
	while ((r = io_uring_peek_cqe(ctx->ring, &cqe)) >= 0) {
		r = handle_completion(ctx, cqe);
		if (r < 0)
			return r;
	}
	return 0;
}

static int do_handle(struct context_s *ctx, size_t how_many)
{
	struct io_uring_cqe *cqe;
	int r;

	while (how_many--) {
		r = io_uring_wait_cqe(ctx->ring, &cqe);
		if (r < 0) {
			fprintf(stderr, "io_uring_wait_cqe: ret=%d: %m\n", r);
			return r;
		}

		r = handle_completion(ctx, cqe);
		if (r < 0)
			return r;
	}

	r = do_peek(ctx);
	if (r < 0) {
		return r;
	}
	return 0;
}

static int do_flush(struct context_s *ctx)
{
	int r;

	r = do_submit_queue(ctx);
	if (r < 0) {
		return r;
	}

	return do_handle(ctx, ctx->infly);
}

static int do_setxattr(struct context_s *ctx, char *path)
{
	struct io_uring_sqe *sqe;
	int r;

	r = do_peek(ctx);
	if (r < 0) {
		free(path);
		return r;
	}

	sqe = io_uring_get_sqe(ctx->ring);
	if (!sqe) {
		if (ctx->infly == 0) {
			fprintf(stderr, "io_uring_get_sqe: %m\n");
			free(path);
			return -1;
		}

		r = do_submit_queue(ctx);
		if (r < 0) {
			return r;
		}

		r = do_handle(ctx, 1);
		if (r < 0) {
			free(path);
			return r;
		}

		sqe = io_uring_get_sqe(ctx->ring);
		if (!sqe) {
			fprintf(stderr, "io_uring_get_sqe: %m\n");
			free(path);
			return -1;
		}
	}

	ctx->infly++;

	io_uring_prep_setxattr(sqe, XATTR_NAME, ctx->value, path, 0, ctx->value_len);
	io_uring_sqe_set_data(sqe, path);
	io_uring_sqe_set_flags(sqe, IOSQE_ASYNC);

	/* Queue a few requests before notifying the kernel.  */
	if (++ctx->reqs % 128 == 0) {
		r = do_submit_queue(ctx);
		if (r < 0) {
			return r;
		}
	}

	return 0;
}

static int recurse(struct context_s *ctx, char *cwd, size_t cwd_len)
{
	struct io_uring *ring = ctx->ring;
	size_t val_len = ctx->value_len;
	const char *val = ctx->value;
	struct dirent *de;
	DIR *d;
	int r = 0;

	d = opendir(cwd);
	if (d == NULL) {
		fprintf(stderr, "opendir `%s`: %m\n", cwd);
		return -1;
	}

	for (de = readdir(d); de; de = readdir(d)) {
		size_t name_len;
		size_t path_len;
		char *path;

		if (strcmp(de->d_name, ".") == 0
		    || strcmp(de->d_name, "..") == 0)
			continue;

		name_len = strlen(de->d_name);
		path = malloc(cwd_len + name_len + 2);
		if (!path)
			return -ENOMEM;

		path_len = cwd_len + name_len + 1;
		memcpy(path, cwd, cwd_len);
		path[cwd_len] = '/';
		memcpy(path + cwd_len + 1, de->d_name, name_len + 1);

		switch (de->d_type) {
		case DT_LNK:
			/* io_uring doesn't currently support lsetxattr.  */
			r = lsetxattr(path, XATTR_NAME,
				      ctx->value, ctx->value_len, 0);
			if (r < 0) {
				fprintf(stderr, "lsetxattr(%s): %m", path);
				return r;
			}
			break;

		case DT_DIR:
			r = recurse(ctx, path, path_len);
			if (r < 0)
				return r;

			r = do_setxattr(ctx, path);
			if (r < 0)
				return r;
			break;

		default:
			r = do_setxattr(ctx, path);
			if (r < 0)
				return r;
			break;
		}
	}

	r = closedir(d);
	if (r < 0)
		return r;

	return r;
}

static int set_and_recurse(struct context_s *ctx, char *path)
{
	int r;

	r = recurse(ctx, path, strlen(path));
	if (r < 0)
		return r;

	return do_setxattr(ctx, path);
}

int main(int argc, char **argv)
{
	struct context_s ctx;
	struct io_uring ring;
	int rc = 0, ret;
	char *it, *path;

	memset(&ctx, 0, sizeof(ctx));

	if (argc != 3) {
		fprintf(stderr, "Usage $CMD $PATH $LABEL\n");
		exit(EXIT_FAILURE);
	}

	ret = io_uring_queue_init(QUEUE_DEPTH, &ring, 0);
	if (ret) {
		fprintf(stderr, "child: ring setup failed: %d\n", ret);
		exit(EXIT_FAILURE);
	}

	if (argv[1][0] == '\0') {
		fprintf(stderr, "invalid path: `%s`\n", argv[1]);
		exit(EXIT_FAILURE);
	}

	it = argv[1] + strlen(argv[1]) - 1;
	while (*it == '/')
		*it-- = '\0';
	if (*it == '\0') {
		fprintf(stderr, "invalid path: `%s`\n", argv[1]);
		exit(EXIT_FAILURE);
	}

	path = strdup(argv[1]);
	if (!path) {
		fprintf(stderr, "strdup: %m");
		exit(EXIT_FAILURE);
	}
	
	ctx.ring = &ring;
	ctx.value = argv[2];
	ctx.value_len = strlen(argv[2]);

	rc = set_and_recurse(&ctx, path);
	if (rc < 0)
		exit(EXIT_FAILURE);

	rc = do_flush(&ctx);

	io_uring_queue_exit(&ring);

	exit(rc ? EXIT_FAILURE : EXIT_SUCCESS);
}