[CRIU] [PATCH 2/3] sfd: Make sure we're not overwriting existing files

[Cyrill Gorcunov]

Just a warn for now since we need to investigate
every case without breaking ci.

Signed-off-by: Cyrill Gorcunov <gorcunov at gmail.com>
---
 criu/include/servicefd.h | 15 +++++++++++++++
 criu/servicefd.c         |  4 ++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/criu/include/servicefd.h b/criu/include/servicefd.h
index f8c2814092b7..1c4349e4eeb0 100644
--- a/criu/include/servicefd.h
+++ b/criu/include/servicefd.h
@@ -1,7 +1,11 @@
 #ifndef __CR_SERVICE_FD_H__
 #define __CR_SERVICE_FD_H__
 
+#include <stdio.h>
 #include <stdbool.h>
+#include <unistd.h>
+
+#include "criu-log.h"
 
 enum sfd_type {
 	SERVICE_FD_MIN,
@@ -28,6 +32,17 @@ enum sfd_type {
 struct pstree_item;
 extern bool sfds_protected;
 
+#define sfd_verify_targtet(_type, _old_fd, _new_fd)					\
+	do {										\
+		char self_path[64];							\
+											\
+		snprintf(self_path, sizeof(self_path), "/proc/self/fd/%d", _new_fd);	\
+		if (access(self_path, F_OK)) {						\
+			pr_warn("type %d: busy target %d -> %d\n",			\
+				_type, _old_fd, _new_fd);				\
+		}									\
+	} while (0)
+
 extern int init_service_fd(void);
 extern int get_service_fd(enum sfd_type type);
 extern bool is_any_service_fd(int fd);
diff --git a/criu/servicefd.c b/criu/servicefd.c
index a9909735af44..bb8c26ca466c 100644
--- a/criu/servicefd.c
+++ b/criu/servicefd.c
@@ -10,8 +10,6 @@
 #include "common/compiler.h"
 #include "common/list.h"
 
-#include "criu-log.h"
-
 #include "util.h"
 #include "bitops.h"
 #include "pstree.h"
@@ -128,6 +126,7 @@ int install_service_fd(enum sfd_type type, int fd)
 		return fd;
 	}
 
+	sfd_verify_targtet(type, fd, sfd);
 	if (dup3(fd, sfd, O_CLOEXEC) != sfd) {
 		pr_perror("Dup %d -> %d failed", fd, sfd);
 		close(fd);
@@ -166,6 +165,7 @@ static void move_service_fd(struct pstree_item *me, int type, int new_id, int ne
 	if (old < 0)
 		return;
 
+	sfd_verify_targtet(type, old, new);
 	ret = dup2(old, new);
 	if (ret == -1) {
 		if (errno != EBADF)
-- 
2.20.1