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/* SPDX-License-Identifier: MIT */
/*
* repro-CVE-2020-29373 -- Reproducer for CVE-2020-29373.
*
* Copyright (c) 2021 SUSE
* Author: Nicolai Stange <nstange@suse.de>
*
* This program 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.
*
* This program 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 this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <fcntl.h>
#include <errno.h>
#include <inttypes.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/wait.h>
#include "liburing.h"
/*
* This attempts to make the kernel issue a sendmsg() to
* path from io_uring's async io_sq_wq_submit_work().
*
* Unfortunately, IOSQE_ASYNC is available only from kernel version
* 5.6 onwards. To still force io_uring to process the request
* asynchronously from io_sq_wq_submit_work(), queue a couple of
* auxiliary requests all failing with EAGAIN before. This is
* implemented by writing repeatedly to an auxiliary O_NONBLOCK
* AF_UNIX socketpair with a small SO_SNDBUF.
*/
static int try_sendmsg_async(const char * const path)
{
int snd_sock, r;
struct io_uring ring;
char sbuf[16] = {};
struct iovec siov = { .iov_base = &sbuf, .iov_len = sizeof(sbuf) };
struct sockaddr_un addr = {};
struct msghdr msg = {
.msg_name = &addr,
.msg_namelen = sizeof(addr),
.msg_iov = &siov,
.msg_iovlen = 1,
};
struct io_uring_cqe *cqe;
struct io_uring_sqe *sqe;
snd_sock = socket(AF_UNIX, SOCK_DGRAM, 0);
if (snd_sock < 0) {
perror("socket(AF_UNIX)");
return -1;
}
addr.sun_family = AF_UNIX;
strcpy(addr.sun_path, path);
r = io_uring_queue_init(512, &ring, 0);
if (r < 0) {
fprintf(stderr, "ring setup failed: %d\n", r);
goto close_iour;
}
sqe = io_uring_get_sqe(&ring);
if (!sqe) {
fprintf(stderr, "get sqe failed\n");
r = -EFAULT;
goto close_iour;
}
/* the actual one supposed to fail with -ENOENT. */
io_uring_prep_sendmsg(sqe, snd_sock, &msg, 0);
sqe->flags = IOSQE_ASYNC;
sqe->user_data = 255;
r = io_uring_submit(&ring);
if (r != 1) {
fprintf(stderr, "sqe submit failed: %d\n", r);
r = -EFAULT;
goto close_iour;
}
r = io_uring_wait_cqe(&ring, &cqe);
if (r < 0) {
fprintf(stderr, "wait completion %d\n", r);
r = -EFAULT;
goto close_iour;
}
if (cqe->user_data != 255) {
fprintf(stderr, "user data %d\n", r);
r = -EFAULT;
goto close_iour;
}
if (cqe->res != -ENOENT) {
r = 3;
fprintf(stderr,
"error: cqe %i: res=%i, but expected -ENOENT\n",
(int)cqe->user_data, (int)cqe->res);
}
io_uring_cqe_seen(&ring, cqe);
close_iour:
io_uring_queue_exit(&ring);
close(snd_sock);
return r;
}
int main(int argc, char *argv[])
{
int r;
char tmpdir[] = "/tmp/tmp.XXXXXX";
int rcv_sock;
struct sockaddr_un addr = {};
pid_t c;
int wstatus;
if (!mkdtemp(tmpdir)) {
perror("mkdtemp()");
return 1;
}
rcv_sock = socket(AF_UNIX, SOCK_DGRAM, 0);
if (rcv_sock < 0) {
perror("socket(AF_UNIX)");
r = 1;
goto rmtmpdir;
}
addr.sun_family = AF_UNIX;
snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/sock", tmpdir);
r = bind(rcv_sock, (struct sockaddr *)&addr,
sizeof(addr));
if (r < 0) {
perror("bind()");
close(rcv_sock);
r = 1;
goto rmtmpdir;
}
c = fork();
if (!c) {
close(rcv_sock);
r = chroot(tmpdir);
if (r) {
if (errno == EPERM) {
fprintf(stderr, "chroot not allowed, skip\n");
return 0;
}
perror("chroot()");
return 1;
}
r = try_sendmsg_async(addr.sun_path);
if (r < 0) {
/* system call failure */
r = 1;
} else if (r) {
/* test case failure */
r += 1;
}
return r;
}
if (waitpid(c, &wstatus, 0) == (pid_t)-1) {
perror("waitpid()");
r = 1;
goto rmsock;
}
if (!WIFEXITED(wstatus)) {
fprintf(stderr, "child got terminated\n");
r = 1;
goto rmsock;
}
r = WEXITSTATUS(wstatus);
if (r)
fprintf(stderr, "error: Test failed\n");
rmsock:
close(rcv_sock);
unlink(addr.sun_path);
rmtmpdir:
rmdir(tmpdir);
return r;
}
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