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process-util: always retry with pidfd_spawn() w/o cgroup first

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Follow-up for 7ac58157ca

With the mentioned commit, iff E2BIG we'd retry pidfd_spawn()
with POSIX_SPAWN_SETCGROUP disabled. However, the same strategy
should actually apply to EOPNOTSUPP/ENOSYS/EPERM too -
they can mean two things here: no clone3() or no CLONE_PIDFD.
Therefore, let's first try clone() + CLONE_PIDFD, and fall further back
to plain clone() (posix_spawn()) only as last resort. Plus, record
the fact so that we don't unnecessarily retry every single time
if CLONE_PIDFD is the one that's unavailable.
This commit is contained in:
Mike Yuan 2024-08-20 20:04:46 +02:00
parent df99a8ef3d
commit e06c5be29a
No known key found for this signature in database
GPG Key ID: 417471C0A40F58B3
1 changed files with 37 additions and 35 deletions
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72
src/basic/process-util.c
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@ -2059,10 +2059,14 @@ int posix_spawn_wrapper(
_unused_ _cleanup_(posix_spawnattr_destroyp) posix_spawnattr_t *attr_destructor = &attr;
#if HAVE_PIDFD_SPAWN
static bool setcgroup_supported = true;
static enum {
CLONE_ONLY_PID,
CLONE_CAN_PIDFD, /* 5.2 */
CLONE_CAN_CGROUP, /* 5.7 */
} clone_support = CLONE_CAN_CGROUP;
_cleanup_close_ int cgroup_fd = -EBADF;
if (cgroup && setcgroup_supported) {
if (cgroup && clone_support >= CLONE_CAN_CGROUP) {
_cleanup_free_ char *resolved_cgroup = NULL;
r = cg_get_path_and_check(
@ -2093,45 +2097,43 @@ int posix_spawn_wrapper(
return -r;
#if HAVE_PIDFD_SPAWN
_cleanup_close_ int pidfd = -EBADF;
if (clone_support >= CLONE_CAN_PIDFD) {
_cleanup_close_ int pidfd = -EBADF;
r = pidfd_spawn(&pidfd, path, NULL, &attr, argv, envp);
if (r == E2BIG && FLAGS_SET(flags, POSIX_SPAWN_SETCGROUP)) {
/* Some kernels (e.g., 5.4) support clone3 but they do not support CLONE_INTO_CGROUP.
* Retry pidfd_spawn() after removing the flag. */
flags &= ~POSIX_SPAWN_SETCGROUP;
r = posix_spawnattr_setflags(&attr, flags);
if (r != 0)
return -r;
r = pidfd_spawn(&pidfd, path, NULL, &attr, argv, envp);
/* if pidfd_spawn was successful after removing SPAWN_CGROUP,
* mark setcgroup_supported as false so that we do not retry every time */
if (r == 0)
setcgroup_supported = false;
}
if (r == 0) {
r = pidref_set_pidfd_consume(ret_pidref, TAKE_FD(pidfd));
if (r < 0)
return r;
return FLAGS_SET(flags, POSIX_SPAWN_SETCGROUP);
}
if (ERRNO_IS_NOT_SUPPORTED(r)) {
/* clone3() could also return EOPNOTSUPP if the target cgroup is in threaded mode. */
if (FLAGS_SET(flags, POSIX_SPAWN_SETCGROUP) && cg_is_threaded(cgroup) > 0)
if (ERRNO_IS_NOT_SUPPORTED(r) && FLAGS_SET(flags, POSIX_SPAWN_SETCGROUP) &&
cg_is_threaded(cgroup) > 0) /* clone3() could also return EOPNOTSUPP if the target cgroup is in threaded mode. */
return -EUCLEAN;
if ((ERRNO_IS_NOT_SUPPORTED(r) || ERRNO_IS_PRIVILEGE(r) || r == E2BIG) &&
FLAGS_SET(flags, POSIX_SPAWN_SETCGROUP)) {
/* Compiled on a newer host, or seccomp&friends blocking clone3()? Fallback, but
* need to disable POSIX_SPAWN_SETCGROUP, which is what redirects to clone3().
* Note that we might get E2BIG here since some kernels (e.g. 5.4) support clone3()
* but not CLONE_INTO_CGROUP. */
/* clone3() not available? */
} else if (!ERRNO_IS_PRIVILEGE(r))
return -r;
/* CLONE_INTO_CGROUP definitely won't work, hence remember the fact so that we don't
* retry every time. */
assert(clone_support >= CLONE_CAN_CGROUP);
clone_support = CLONE_CAN_PIDFD;
/* Compiled on a newer host, or seccomp&friends blocking clone3()? Fallback, but need to change the
* flags to remove the cgroup one, which is what redirects to clone3() */
if (FLAGS_SET(flags, POSIX_SPAWN_SETCGROUP)) {
flags &= ~POSIX_SPAWN_SETCGROUP;
r = posix_spawnattr_setflags(&attr, flags);
if (r != 0)
flags &= ~POSIX_SPAWN_SETCGROUP;
r = posix_spawnattr_setflags(&attr, flags);
if (r != 0)
return -r;
r = pidfd_spawn(&pidfd, path, NULL, &attr, argv, envp);
}
if (r == 0) {
r = pidref_set_pidfd_consume(ret_pidref, TAKE_FD(pidfd));
if (r < 0)
return r;
return FLAGS_SET(flags, POSIX_SPAWN_SETCGROUP);
}
if (!ERRNO_IS_NOT_SUPPORTED(r) && !ERRNO_IS_PRIVILEGE(r))
return -r;
clone_support = CLONE_ONLY_PID; /* No CLONE_PIDFD either? */
}
#endif