crtools: Make close_cr_fdset being safe to be called with closed fd-set

It was being done intentionally to be able to call close_cr_fdset
several times in a row, bring this ability back. Otherwise I'm
getting glibc complains about attemt to free already freed memory.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>

cr-dump.c

@@ -1233,11 +1233,11 @@ int cr_dump_tasks(pid_t pid, struct cr_options *opts)
 				if (dump_task_thread(item->threads[i], cr_fdset_thread))
 					goto err;
 
-				close_cr_fdset(cr_fdset_thread);
+				close_cr_fdset(&cr_fdset_thread);
 			}
 		}
 
-		close_cr_fdset(cr_fdset);
+		close_cr_fdset(&cr_fdset);
 
 		if (opts->leader_only)
 			break;
@@ -1256,8 +1256,8 @@ err:
 
 	free_pstree(&pstree_list);
 
-	close_cr_fdset(cr_fdset);
-	close_cr_fdset(cr_fdset_thread);
+	close_cr_fdset(&cr_fdset);
+	close_cr_fdset(&cr_fdset_thread);
 
 	return ret;
 }

cr-show.c

@@ -512,7 +512,7 @@ static int cr_show_all(unsigned long pid, struct cr_options *opts)
 	lseek(cr_fdset->fds[CR_FD_PSTREE], MAGIC_OFFSET, SEEK_SET);
 	show_pstree(cr_fdset->fds[CR_FD_PSTREE]);
 
-	close_cr_fdset(cr_fdset);
+	close_cr_fdset(&cr_fdset);
 
 	list_for_each_entry(item, &pstree_list, list) {
 
@@ -545,7 +545,7 @@ static int cr_show_all(unsigned long pid, struct cr_options *opts)
 
 				pr_info("----------------------------------------\n");
 
-				close_cr_fdset(cr_fdset_th);
+				close_cr_fdset(&cr_fdset_th);
 			}
 		}
 
@@ -559,7 +559,7 @@ static int cr_show_all(unsigned long pid, struct cr_options *opts)
 
 		show_unixsk(cr_fdset->fds[CR_FD_UNIXSK]);
 
-		close_cr_fdset(cr_fdset);
+		close_cr_fdset(&cr_fdset);
 
 		if (opts->leader_only)
 			break;
@@ -567,7 +567,7 @@ static int cr_show_all(unsigned long pid, struct cr_options *opts)
 
 out:
 	free_pstree(&pstree_list);
-	close_cr_fdset(cr_fdset);
+	close_cr_fdset(&cr_fdset);
 	return ret;
 }
 

crtools.c

@@ -180,23 +180,27 @@ err:
 	return cr_fdset;
 }
 
-void close_cr_fdset(struct cr_fdset *cr_fdset)
+void close_cr_fdset(struct cr_fdset **cr_fdset)
 {
+	struct cr_fdset *fdset;
 	unsigned int i;
 
-	if (!cr_fdset)
+	if (!cr_fdset || !*cr_fdset)
 		return;
 
+	fdset = *cr_fdset;
+
 	for (i = 0; i < CR_FD_MAX; i++) {
-		if (cr_fdset->fds[i] == -1)
+		if (fdset->fds[i] == -1)
 			continue;
 
-		pr_debug("Closed %d/%d\n", i, cr_fdset->fds[i]);
-		close(cr_fdset->fds[i]);
-		cr_fdset->fds[i] = -1;
+		pr_debug("Closed %d/%d\n", i, fdset->fds[i]);
+		close(fdset->fds[i]);
+		fdset->fds[i] = -1;
 	}
 
-	free(cr_fdset);
+	xfree(fdset);
+	*cr_fdset = NULL;
 }
 
 int get_image_path(char *path, int size, const char *fmt, int pid)

include/crtools.h

@@ -87,7 +87,7 @@ int convert_to_elf(char *elf_path, int fd_core);
 
 struct cr_fdset *prep_cr_fdset_for_dump(int pid, unsigned long use_mask);
 struct cr_fdset *prep_cr_fdset_for_restore(int pid, unsigned long use_mask);
-void close_cr_fdset(struct cr_fdset *cr_fdset);
+void close_cr_fdset(struct cr_fdset **cr_fdset);
 
 void free_mappings(struct list_head *vma_area_list);