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passt/pasta.c
Stefano Brivio 2aea1da143 treewide: Allow additional system calls for i386/i686
I haven't tested i386 for a long time (after playing with some
openSUSE i586 image a couple of years ago). It turns out that a number
of system calls we actually need were denied by the seccomp filter,
and not even basic functionality works.

Add some system calls that glibc started using with the 64-bit time
("t64") transition, see also:

  https://wiki.debian.org/ReleaseGoals/64bit-time

that is: clock_gettime64, timerfd_gettime64, fcntl64, and
recvmmsg_time64.

Add further system calls that are needed regardless of time_t width,
that is, mmap2 (valgrind profile only), _llseek and sigreturn (common
outside x86_64), and socketcall (same as s390x).

I validated this against an almost full run of the test suite, with
just a few selected tests skipped. Fixes needed to run most tests on
i386/i686, and other assorted fixes for tests, are included in
upcoming patches.

Reported-by: Uroš Knupleš <uros@knuples.net>
Analysed-by: Faidon Liambotis <paravoid@debian.org>
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1078981
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
2024-08-21 12:00:43 +02:00

524 lines
13 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* PASST - Plug A Simple Socket Transport
* for qemu/UNIX domain socket mode
*
* PASTA - Pack A Subtle Tap Abstraction
* for network namespace/tap device mode
*
* pasta.c - pasta (namespace) specific implementations
*
* Copyright (c) 2020-2021 Red Hat GmbH
* Author: Stefano Brivio <sbrivio@redhat.com>
*
* #syscalls:pasta clone waitid exit exit_group rt_sigprocmask
* #syscalls:pasta rt_sigreturn|sigreturn
* #syscalls:pasta arm:sigreturn ppc64:sigreturn s390x:sigreturn i686:sigreturn
*/
#include <sched.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <libgen.h>
#include <limits.h>
#include <stdlib.h>
#include <stdbool.h>
#include <stdint.h>
#include <unistd.h>
#include <syslog.h>
#include <sys/epoll.h>
#include <sys/inotify.h>
#include <sys/mount.h>
#include <sys/timerfd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/statfs.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <signal.h>
#include <dirent.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <net/ethernet.h>
#include <sys/syscall.h>
#include <linux/magic.h>
#include "util.h"
#include "passt.h"
#include "isolation.h"
#include "netlink.h"
#include "log.h"
#define HOSTNAME_PREFIX "pasta-"
/* PID of child, in case we created a namespace */
int pasta_child_pid;
/**
* pasta_child_handler() - Exit once shell exits (if we started it), reap clones
* @signal: Unused, handler deals with SIGCHLD only
*/
void pasta_child_handler(int signal)
{
int errno_save = errno;
siginfo_t infop;
(void)signal;
if (signal != SIGCHLD)
return;
if (pasta_child_pid &&
!waitid(P_PID, pasta_child_pid, &infop, WEXITED | WNOHANG)) {
if (infop.si_pid == pasta_child_pid) {
if (infop.si_code == CLD_EXITED)
exit(infop.si_status);
/* If killed by a signal, si_status is the number.
* Follow common shell convention of returning it + 128.
*/
exit(infop.si_status + 128);
/* Nothing to do, detached PID namespace going away */
}
}
waitid(P_ALL, 0, NULL, WEXITED | WNOHANG);
waitid(P_ALL, 0, NULL, WEXITED | WNOHANG);
errno = errno_save;
}
/**
* pasta_wait_for_ns() - Busy loop until we can enter the target namespace
* @arg: Execution context
*
* Return: 0
*/
static int pasta_wait_for_ns(void *arg)
{
struct ctx *c = (struct ctx *)arg;
int flags = O_RDONLY | O_CLOEXEC;
char ns[PATH_MAX];
snprintf(ns, PATH_MAX, "/proc/%i/ns/net", pasta_child_pid);
do {
while ((c->pasta_netns_fd = open(ns, flags)) < 0) {
if (errno != ENOENT)
return 0;
}
} while (setns(c->pasta_netns_fd, CLONE_NEWNET) &&
!close(c->pasta_netns_fd));
return 0;
}
/**
* ns_check() - Check if we can enter configured namespaces
* @arg: Execution context
*
* Return: 0
*/
static int ns_check(void *arg)
{
struct ctx *c = (struct ctx *)arg;
if (setns(c->pasta_netns_fd, CLONE_NEWNET))
c->pasta_netns_fd = -1;
return 0;
}
/**
* pasta_open_ns() - Open network namespace descriptors
* @c: Execution context
* @netns: network namespace path
*
* Return: 0 on success, negative error code otherwise
*/
void pasta_open_ns(struct ctx *c, const char *netns)
{
int nfd = -1;
nfd = open(netns, O_RDONLY | O_CLOEXEC);
if (nfd < 0)
die_perror("Couldn't open network namespace %s", netns);
c->pasta_netns_fd = nfd;
NS_CALL(ns_check, c);
if (c->pasta_netns_fd < 0)
die_perror("Couldn't switch to pasta namespaces");
if (!c->no_netns_quit) {
char buf[PATH_MAX] = { 0 };
strncpy(buf, netns, PATH_MAX - 1);
strncpy(c->netns_base, basename(buf), PATH_MAX - 1);
strncpy(buf, netns, PATH_MAX - 1);
strncpy(c->netns_dir, dirname(buf), PATH_MAX - 1);
}
}
/**
* struct pasta_spawn_cmd_arg - Argument for pasta_spawn_cmd()
* @exe: Executable to run
* @argv: Command and arguments to run
*/
struct pasta_spawn_cmd_arg {
const char *exe;
char *const *argv;
};
/**
* pasta_spawn_cmd() - Prepare new netns, start command or shell
* @arg: See @pasta_spawn_cmd_arg
*
* Return: this function never returns
*/
/* cppcheck-suppress [constParameterCallback, unmatchedSuppression] */
static int pasta_spawn_cmd(void *arg)
{
char hostname[HOST_NAME_MAX + 1] = HOSTNAME_PREFIX;
const struct pasta_spawn_cmd_arg *a;
sigset_t set;
/* We run in a detached PID and mount namespace: mount /proc over */
if (mount("", "/proc", "proc", 0, NULL))
warn_perror("Couldn't mount /proc");
if (write_file("/proc/sys/net/ipv4/ping_group_range", "0 0"))
warn("Cannot set ping_group_range, ICMP requests might fail");
if (!gethostname(hostname + sizeof(HOSTNAME_PREFIX) - 1,
HOST_NAME_MAX + 1 - sizeof(HOSTNAME_PREFIX)) ||
errno == ENAMETOOLONG) {
hostname[HOST_NAME_MAX] = '\0';
if (sethostname(hostname, strlen(hostname)))
warn("Unable to set pasta-prefixed hostname");
}
/* Wait for the parent to be ready: see main() */
sigemptyset(&set);
sigaddset(&set, SIGUSR1);
sigwaitinfo(&set, NULL);
a = (const struct pasta_spawn_cmd_arg *)arg;
execvp(a->exe, a->argv);
die_perror("Failed to start command or shell");
}
/**
* pasta_start_ns() - Fork command in new namespace if target ns is not given
* @c: Execution context
* @uid: UID we're running as in the init namespace
* @gid: GID we're running as in the init namespace
* @argc: Number of arguments for spawned command
* @argv: Command to spawn and arguments
*/
void pasta_start_ns(struct ctx *c, uid_t uid, gid_t gid,
int argc, char *argv[])
{
char ns_fn_stack[NS_FN_STACK_SIZE]
__attribute__ ((aligned(__alignof__(max_align_t))));
struct pasta_spawn_cmd_arg arg = {
.exe = argv[0],
.argv = argv,
};
char uidmap[BUFSIZ], gidmap[BUFSIZ];
char *sh_argv[] = { NULL, NULL };
char sh_arg0[PATH_MAX + 1];
sigset_t set;
c->foreground = 1;
if (!c->debug)
c->quiet = 1;
/* Configure user and group mappings */
snprintf(uidmap, BUFSIZ, "0 %u 1", uid);
snprintf(gidmap, BUFSIZ, "0 %u 1", gid);
if (write_file("/proc/self/uid_map", uidmap) ||
write_file("/proc/self/setgroups", "deny") ||
write_file("/proc/self/gid_map", gidmap)) {
warn("Couldn't configure user mappings");
}
if (argc == 0) {
arg.exe = getenv("SHELL");
if (!arg.exe)
arg.exe = "/bin/sh";
if ((size_t)snprintf(sh_arg0, sizeof(sh_arg0),
"-%s", arg.exe) >= sizeof(sh_arg0))
die("$SHELL is too long (%zu bytes)", strlen(arg.exe));
sh_argv[0] = sh_arg0;
arg.argv = sh_argv;
}
/* Block SIGUSR1 in child, we queue it in main() when we're ready */
sigemptyset(&set);
sigaddset(&set, SIGUSR1);
sigprocmask(SIG_BLOCK, &set, NULL);
pasta_child_pid = do_clone(pasta_spawn_cmd, ns_fn_stack,
sizeof(ns_fn_stack),
CLONE_NEWIPC | CLONE_NEWPID | CLONE_NEWNET |
CLONE_NEWUTS | CLONE_NEWNS | SIGCHLD,
(void *)&arg);
if (pasta_child_pid == -1)
die_perror("Failed to clone process with detached namespaces");
NS_CALL(pasta_wait_for_ns, c);
if (c->pasta_netns_fd < 0)
die_perror("Failed to join network namespace");
}
/**
* pasta_ns_conf() - Set up loopback and tap interfaces in namespace as needed
* @c: Execution context
*/
void pasta_ns_conf(struct ctx *c)
{
int rc = 0;
rc = nl_link_set_flags(nl_sock_ns, 1 /* lo */, IFF_UP, IFF_UP);
if (rc < 0)
die("Couldn't bring up loopback interface in namespace: %s",
strerror(-rc));
/* Get or set MAC in target namespace */
if (MAC_IS_ZERO(c->guest_mac))
nl_link_get_mac(nl_sock_ns, c->pasta_ifi, c->guest_mac);
else
rc = nl_link_set_mac(nl_sock_ns, c->pasta_ifi, c->guest_mac);
if (rc < 0)
die("Couldn't set MAC address in namespace: %s",
strerror(-rc));
if (c->pasta_conf_ns) {
unsigned int flags = IFF_UP;
if (c->mtu != -1)
nl_link_set_mtu(nl_sock_ns, c->pasta_ifi, c->mtu);
if (c->ifi6) /* Avoid duplicate address detection on link up */
flags |= IFF_NOARP;
nl_link_set_flags(nl_sock_ns, c->pasta_ifi, flags, flags);
if (c->ifi4) {
if (c->ip4.no_copy_addrs) {
rc = nl_addr_set(nl_sock_ns, c->pasta_ifi,
AF_INET,
&c->ip4.addr,
c->ip4.prefix_len);
} else {
rc = nl_addr_dup(nl_sock, c->ifi4,
nl_sock_ns, c->pasta_ifi,
AF_INET);
}
if (rc < 0) {
die("Couldn't set IPv4 address(es) in namespace: %s",
strerror(-rc));
}
if (c->ip4.no_copy_routes) {
rc = nl_route_set_def(nl_sock_ns, c->pasta_ifi,
AF_INET,
&c->ip4.guest_gw);
} else {
rc = nl_route_dup(nl_sock, c->ifi4, nl_sock_ns,
c->pasta_ifi, AF_INET);
}
if (rc < 0) {
die("Couldn't set IPv4 route(s) in guest: %s",
strerror(-rc));
}
}
if (c->ifi6) {
rc = nl_addr_get_ll(nl_sock_ns, c->pasta_ifi,
&c->ip6.addr_ll_seen);
if (rc < 0) {
warn("Can't get LL address from namespace: %s",
strerror(-rc));
}
rc = nl_addr_set_ll_nodad(nl_sock_ns, c->pasta_ifi);
if (rc < 0) {
warn("Can't set nodad for LL in namespace: %s",
strerror(-rc));
}
/* We dodged DAD: re-enable neighbour solicitations */
nl_link_set_flags(nl_sock_ns, c->pasta_ifi,
0, IFF_NOARP);
if (c->ip6.no_copy_addrs) {
rc = nl_addr_set(nl_sock_ns, c->pasta_ifi,
AF_INET6, &c->ip6.addr, 64);
} else {
rc = nl_addr_dup(nl_sock, c->ifi6,
nl_sock_ns, c->pasta_ifi,
AF_INET6);
}
if (rc < 0) {
die("Couldn't set IPv6 address(es) in namespace: %s",
strerror(-rc));
}
if (c->ip6.no_copy_routes) {
rc = nl_route_set_def(nl_sock_ns, c->pasta_ifi,
AF_INET6,
&c->ip6.guest_gw);
} else {
rc = nl_route_dup(nl_sock, c->ifi6,
nl_sock_ns, c->pasta_ifi,
AF_INET6);
}
if (rc < 0) {
die("Couldn't set IPv6 route(s) in guest: %s",
strerror(-rc));
}
}
}
proto_update_l2_buf(c->guest_mac, NULL);
}
/**
* pasta_netns_quit_timer() - Set up fallback timer to monitor namespace
*
* Return: timerfd file descriptor, negative error code on failure
*/
static int pasta_netns_quit_timer(void)
{
int fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
struct itimerspec it = { { 1, 0 }, { 1, 0 } }; /* one-second interval */
if (fd == -1) {
err_perror("Failed to create timerfd for quit timer");
return -errno;
}
if (timerfd_settime(fd, 0, &it, NULL) < 0) {
err_perror("Failed to set interval for quit timer");
close(fd);
return -errno;
}
return fd;
}
/**
* pasta_netns_quit_init() - Watch network namespace to quit once it's gone
* @c: Execution context
*/
void pasta_netns_quit_init(const struct ctx *c)
{
union epoll_ref ref = { .type = EPOLL_TYPE_NSQUIT_INOTIFY };
struct epoll_event ev = { .events = EPOLLIN };
int flags = O_NONBLOCK | O_CLOEXEC;
struct statfs s = { 0 };
bool try_inotify = true;
int fd = -1, dir_fd;
if (c->mode != MODE_PASTA || c->no_netns_quit || !*c->netns_base)
return;
if ((dir_fd = open(c->netns_dir, O_CLOEXEC | O_RDONLY)) < 0)
die("netns dir open: %s, exiting", strerror(errno));
if (fstatfs(dir_fd, &s) || s.f_type == DEVPTS_SUPER_MAGIC ||
s.f_type == PROC_SUPER_MAGIC || s.f_type == SYSFS_MAGIC)
try_inotify = false;
if (try_inotify && (fd = inotify_init1(flags)) < 0)
warn("inotify_init1(): %s, use a timer", strerror(errno));
if (fd >= 0 && inotify_add_watch(fd, c->netns_dir, IN_DELETE) < 0) {
warn("inotify_add_watch(): %s, use a timer",
strerror(errno));
close(fd);
fd = -1;
}
if (fd < 0) {
if ((fd = pasta_netns_quit_timer()) < 0)
die("Failed to set up fallback netns timer, exiting");
ref.nsdir_fd = dir_fd;
ref.type = EPOLL_TYPE_NSQUIT_TIMER;
} else {
close(dir_fd);
}
if (fd > FD_REF_MAX)
die("netns monitor file number %i too big, exiting", fd);
ref.fd = fd;
ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, fd, &ev);
}
/**
* pasta_netns_quit_inotify_handler() - Handle inotify watch, exit if ns is gone
* @c: Execution context
* @inotify_fd: inotify file descriptor with watch on namespace directory
*/
void pasta_netns_quit_inotify_handler(struct ctx *c, int inotify_fd)
{
char buf[sizeof(struct inotify_event) + NAME_MAX + 1];
const struct inotify_event *in_ev = (struct inotify_event *)buf;
if (read(inotify_fd, buf, sizeof(buf)) < (ssize_t)sizeof(*in_ev))
return;
if (strncmp(in_ev->name, c->netns_base, sizeof(c->netns_base)))
return;
info("Namespace %s is gone, exiting", c->netns_base);
exit(EXIT_SUCCESS);
}
/**
* pasta_netns_quit_timer_handler() - Handle timer, exit if ns is gone
* @c: Execution context
* @ref: epoll reference for timer descriptor
*/
void pasta_netns_quit_timer_handler(struct ctx *c, union epoll_ref ref)
{
uint64_t expirations;
ssize_t n;
int fd;
n = read(ref.fd, &expirations, sizeof(expirations));
if (n < 0)
die_perror("Namespace watch timer read() error");
if ((size_t)n < sizeof(expirations))
warn("Namespace watch timer: short read(): %zi", n);
fd = openat(ref.nsdir_fd, c->netns_base, O_PATH | O_CLOEXEC);
if (fd < 0) {
if (errno == EACCES) /* Expected for existing procfs entry */
return;
info("Namespace %s is gone, exiting", c->netns_base);
exit(EXIT_SUCCESS);
}
close(fd);
}