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conf: attach devpts mount directly when new mount api can be used

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Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This commit is contained in:
Christian Brauner
2021-07-29 10:46:59 +02:00
parent a32e275f25
commit f30fc74d07
1 changed files with 28 additions and 17 deletions
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45
src/lxc/conf.c
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@@ -1667,14 +1667,27 @@ static int lxc_prepare_devpts_child(struct lxc_handler *handler)
{ {
__do_close int fd_fs = -EBADF, fd_fsmnt = -EBADF; __do_close int fd_fs = -EBADF, fd_fsmnt = -EBADF;
struct lxc_conf *conf = handler->conf; struct lxc_conf *conf = handler->conf;
struct lxc_rootfs *rootfs = &conf->rootfs;
int ret; int ret;
if (!can_use_mount_api())
return 0;
if (conf->pty_max <= 0) if (conf->pty_max <= 0)
return log_debug(0, "No new devpts instance will be mounted since no pts devices are requested"); return log_debug(0, "No new devpts instance will be mounted since no pts devices are requested");
ret = strnprintf(rootfs->buf, sizeof(rootfs->buf),
"/proc/self/fd/%d/pts", rootfs->dfd_dev);
if (ret < 0)
return syserror("Failed to create path");
(void)umount2(rootfs->buf, MNT_DETACH);
/* Create mountpoint for devpts instance. */
ret = mkdirat(rootfs->dfd_dev, "pts", 0755);
if (ret < 0 && errno != EEXIST)
return log_error_errno(-1, errno, "Failed to create \"/dev/pts\" directory");
if (!can_use_mount_api())
return 0;
fd_fs = fs_prepare("devpts", -EBADF, "", 0, 0); fd_fs = fs_prepare("devpts", -EBADF, "", 0, 0);
if (fd_fs < 0) if (fd_fs < 0)
return syserror("Failed to prepare filesystem context for devpts"); return syserror("Failed to prepare filesystem context for devpts");
@@ -1710,10 +1723,14 @@ static int lxc_prepare_devpts_child(struct lxc_handler *handler)
fd_fsmnt = fsmount(fd_fs, FSMOUNT_CLOEXEC, MOUNT_ATTR_NOSUID | MOUNT_ATTR_NOEXEC); fd_fsmnt = fsmount(fd_fs, FSMOUNT_CLOEXEC, MOUNT_ATTR_NOSUID | MOUNT_ATTR_NOEXEC);
if (fd_fsmnt < 0) if (fd_fsmnt < 0)
return syserror("Failed to create new mount for filesystem context %d", fd_fs); return syserror("Failed to create new mount for filesystem context %d", fd_fs);
TRACE("Created detached devpts mount %d", fd_fsmnt); TRACE("Created detached devpts mount %d", fd_fsmnt);
handler->conf->devpts_fd = move_fd(fd_fsmnt);
ret = move_mount(fd_fsmnt, "", rootfs->dfd_dev, "pts", MOVE_MOUNT_F_EMPTY_PATH);
if (ret)
return syserror("Failed to attach devpts mount %d to %d/pts", conf->devpts_fd, rootfs->dfd_dev);
DEBUG("Attached detached devpts mount %d to %d/pts", fd_fsmnt, rootfs->dfd_dev);
handler->conf->devpts_fd = move_fd(fd_fsmnt);
return 0; return 0;
} }
@@ -1730,19 +1747,14 @@ static int lxc_finalize_devpts_child(struct lxc_handler *handler)
if (conf->pty_max <= 0) if (conf->pty_max <= 0)
return log_debug(0, "No new devpts instance will be mounted since no pts devices are requested"); return log_debug(0, "No new devpts instance will be mounted since no pts devices are requested");
/* if (!can_use_mount_api()) {
* Fallback codepath in case the new mount API can't be used to create
* detached mounts.
*/
if (conf->devpts_fd >= 0) {
ret = move_mount(conf->devpts_fd, "", rootfs->dfd_dev, "pts", MOVE_MOUNT_F_EMPTY_PATH);
if (ret)
return syserror("Failed to attach devpts mount %d to %d/pts", conf->devpts_fd, rootfs->dfd_dev);
DEBUG("Attached detached devpts mount %d to %d/pts", conf->devpts_fd, rootfs->dfd_dev);
} else {
__do_close int devpts_fd = -EBADF; __do_close int devpts_fd = -EBADF;
/*
* Fallback codepath in case the new mount API can't be used to
* create detached mounts.
*/
ret = strnprintf(devpts_mntopts, sizeof(devpts_mntopts), "%s,max=%zu", ret = strnprintf(devpts_mntopts, sizeof(devpts_mntopts), "%s,max=%zu",
default_devpts_mntopts, conf->pty_max); default_devpts_mntopts, conf->pty_max);
if (ret < 0) if (ret < 0)
@@ -1776,7 +1788,6 @@ static int lxc_finalize_devpts_child(struct lxc_handler *handler)
if (ret == 0) if (ret == 0)
break; break;
} }
if (ret < 0) if (ret < 0)
return log_error_errno(-1, errno, "Failed to mount new devpts instance"); return log_error_errno(-1, errno, "Failed to mount new devpts instance");