[CRIU] [PATCH 4/5] files: open files on overmounted mounts are not supported

[Pavel Tikhomirov]

Files from such mounts can switch on restore to different files on the
overmounting mount, as we yet don't fully control the mount on which
the file is restored.

Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 criu/files-reg.c     | 13 +++++++++----
 criu/include/mount.h |  1 +
 criu/mount.c         |  2 +-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/criu/files-reg.c b/criu/files-reg.c
index e3ed01f55..f7247e488 100644
--- a/criu/files-reg.c
+++ b/criu/files-reg.c
@@ -1288,7 +1288,7 @@ static bool should_check_size(int flags)
 int dump_one_reg_file(int lfd, u32 id, const struct fd_parms *p)
 {
 	struct fd_link _link, *link;
-	struct ns_id *nsid;
+	struct mount_info *mi;
 	struct cr_img *rimg;
 	char ext_id[64];
 	FileEntry fe = FILE_ENTRY__INIT;
@@ -1312,13 +1312,18 @@ int dump_one_reg_file(int lfd, u32 id, const struct fd_parms *p)
 		goto ext;
 	}
 
-	nsid = lookup_nsid_by_mnt_id(p->mnt_id);
-	if (nsid == NULL) {
+	mi = lookup_mnt_id(p->mnt_id);
+	if (mi == NULL) {
 		pr_err("Can't lookup mount=%d for fd=%d path=%s\n",
 			p->mnt_id, p->fd, link->name + 1);
 		return -1;
 	}
 
+	if (mnt_is_overmounted(mi)) {
+		pr_err("Open files on overmounted mounts are not supported yet\n");
+		return -1;
+	}
+
 	if (p->mnt_id >= 0 && (root_ns_mask & CLONE_NEWNS)) {
 		rfe.mnt_id = p->mnt_id;
 		rfe.has_mnt_id = true;
@@ -1335,7 +1340,7 @@ int dump_one_reg_file(int lfd, u32 id, const struct fd_parms *p)
 		return -1;
 	}
 
-	if (check_path_remap(link, p, lfd, id, nsid))
+	if (check_path_remap(link, p, lfd, id, mi->nsid))
 		return -1;
 	rfe.name	= &link->name[1];
 ext:
diff --git a/criu/include/mount.h b/criu/include/mount.h
index 776c348cd..43cfe788a 100644
--- a/criu/include/mount.h
+++ b/criu/include/mount.h
@@ -129,5 +129,6 @@ extern struct mount_info *parse_mountinfo(pid_t pid, struct ns_id *nsid, bool fo
 extern int check_mnt_id(void);
 
 extern int remount_readonly_mounts(void);
+extern int mnt_is_overmounted(struct mount_info *mi);
 
 #endif /* __CR_MOUNT_H__ */
diff --git a/criu/mount.c b/criu/mount.c
index 3c19c280b..c28af0fe2 100644
--- a/criu/mount.c
+++ b/criu/mount.c
@@ -1152,7 +1152,7 @@ static int get_clean_fd(struct mount_info *mi)
  * root of our mount namespace as it is covered by other mount.
  * mnt_is_overmounted() checks if mount is not visible.
  */
-static int mnt_is_overmounted(struct mount_info *mi)
+int mnt_is_overmounted(struct mount_info *mi)
 {
 	struct mount_info *t, *c, *m = mi;
 
-- 
2.17.1