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mount-util: split remount_idmap() in two

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This will make things a bit longer for now, but more powerful as we can
reuse the userns fd between calls to remount_idmap() if we need to
adjust multiple mounts.

No change in behaviour, just some minor refactoring.
This commit is contained in:
Lennart Poettering 2023-03-14 22:55:32 +01:00
parent 4054d76151
commit 17b798d915
2 changed files with 20 additions and 15 deletions
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33
src/shared/mount-util.c
View File

@ -1080,13 +1080,16 @@ int make_mount_point(const char *path) {
return 1;
}
static int make_userns(uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping) {
int make_userns(uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping) {
_cleanup_close_ int userns_fd = -EBADF;
_cleanup_free_ char *line = NULL;
/* Allocates a userns file descriptor with the mapping we need. For this we'll fork off a child
* process whose only purpose is to give us a new user namespace. It's killed when we got it. */
if (!userns_shift_range_valid(uid_shift, uid_range))
return -EINVAL;
if (IN_SET(idmapping, REMOUNT_IDMAPPING_NONE, REMOUNT_IDMAPPING_HOST_ROOT)) {
if (asprintf(&line, UID_FMT " " UID_FMT " " UID_FMT "\n", 0u, uid_shift, uid_range) < 0)
return log_oom_debug();
@ -1125,31 +1128,21 @@ static int make_userns(uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdm
return TAKE_FD(userns_fd);
}
int remount_idmap(
int remount_idmap_fd(
const char *p,
uid_t uid_shift,
uid_t uid_range,
uid_t owner,
RemountIdmapping idmapping) {
int userns_fd) {
_cleanup_close_ int mount_fd = -EBADF, userns_fd = -EBADF;
_cleanup_close_ int mount_fd = -EBADF;
int r;
assert(p);
if (!userns_shift_range_valid(uid_shift, uid_range))
return -EINVAL;
assert(userns_fd >= 0);
/* Clone the mount point */
mount_fd = open_tree(-1, p, OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
if (mount_fd < 0)
return log_debug_errno(errno, "Failed to open tree of mounted filesystem '%s': %m", p);
/* Create a user namespace mapping */
userns_fd = make_userns(uid_shift, uid_range, owner, idmapping);
if (userns_fd < 0)
return userns_fd;
/* Set the user namespace mapping attribute on the cloned mount point */
if (mount_setattr(mount_fd, "", AT_EMPTY_PATH | AT_RECURSIVE,
&(struct mount_attr) {
@ -1170,6 +1163,16 @@ int remount_idmap(
return 0;
}
int remount_idmap(const char *p, uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping) {
_cleanup_close_ int userns_fd = -EBADF;
userns_fd = make_userns(uid_shift, uid_range, owner, idmapping);
if (userns_fd < 0)
return userns_fd;
return remount_idmap_fd(p, userns_fd);
}
typedef struct SubMount {
char *path;
int mount_fd;

2
src/shared/mount-util.h
View File

@ -103,6 +103,8 @@ typedef enum RemountIdmapping {
_REMOUNT_IDMAPPING_INVALID = -EINVAL,
} RemountIdmapping;
int make_userns(uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping);
int remount_idmap_fd(const char *p, int userns_fd);
int remount_idmap(const char *p, uid_t uid_shift, uid_t uid_range, uid_t owner, RemountIdmapping idmapping);
int remount_and_move_sub_mounts(