config/files-reg: Add opt to skip file r/w/x check on restore

A file's r/w/x changing between checkpoint and restore does
not necessarily imply that something is wrong. For example,
if a process opens a file having perms rw- for reading and
we change the perms to r--, the process can be restored and
will function as expected.

Therefore, this patch adds an option

--skip-file-rwx-check

to disable this check on restore. File validation is unaffected
and should still function as expected with respect to the content
of files.

Signed-off-by: Younes Manton <ymanton@ca.ibm.com>

Documentation/criu.txt

@@ -668,6 +668,9 @@ The 'mode' may be one of the following:
                 build-ID cannot be obtained, 'chksm-first' method will be
                 used. This is the default if mode is unspecified.
 
+*--skip-file-rwx-check*::
+    Skip checking file permissions (r/w/x for u/g/o) on restore.
+
 *check*
 ~~~~~~~
 Checks whether the kernel supports the features needed by *criu* to

criu/config.c

@@ -696,6 +696,7 @@ int parse_options(int argc, char **argv, bool *usage_error, bool *has_exec_cmd,
 		{ "cgroup-yard", required_argument, 0, 1096 },
 		{ "pre-dump-mode", required_argument, 0, 1097 },
 		{ "file-validation", required_argument, 0, 1098 },
+		BOOL_OPT("skip-file-rwx-check", &opts.skip_file_rwx_check),
 		{ "lsm-mount-context", required_argument, 0, 1099 },
 		{ "network-lock", required_argument, 0, 1100 },
 		BOOL_OPT("mntns-compat-mode", &opts.mntns_compat_mode),

criu/cr-service.c

@@ -464,6 +464,9 @@ static int setup_opts_from_req(int sk, CriuOpts *req)
 	if (req->has_shell_job)
 		opts.shell_job = req->shell_job;
 
+	if (req->has_skip_file_rwx_check)
+		opts.skip_file_rwx_check = req->skip_file_rwx_check;
+
 	if (req->has_file_locks)
 		opts.handle_file_locks = req->file_locks;
 

criu/crtools.c

@@ -504,6 +504,9 @@ usage:
 	       "  --file-validation METHOD\n"
 	       "			pass the validation method to be used; argument\n"
 	       "			can be 'filesize' or 'buildid' (default).\n"
+	       "  --skip-file-rwx-check\n"
+	       "			Skip checking file permissions\n"
+	       "			(r/w/x for u/g/o) on restore.\n"
 	       "\n"
 	       "Check options:\n"
 	       "  Without options, \"criu check\" checks availability of absolutely required\n"

criu/files-reg.c

@@ -2199,9 +2199,21 @@ ext:
 		if (!validate_file(tmp, &st, rfi))
 			goto err;
 
-		if (rfi->rfe->has_mode && (st.st_mode != rfi->rfe->mode)) {
-			pr_err("File %s has bad mode 0%o (expect 0%o)\n", rfi->path, (int)st.st_mode, rfi->rfe->mode);
-			goto err;
+		if (rfi->rfe->has_mode) {
+			mode_t curr_mode = st.st_mode;
+			mode_t saved_mode = rfi->rfe->mode;
+
+			if (opts.skip_file_rwx_check) {
+				curr_mode &= ~(S_IRWXU | S_IRWXG | S_IRWXO);
+				saved_mode &= ~(S_IRWXU | S_IRWXG | S_IRWXO);
+			}
+
+			if (curr_mode != saved_mode) {
+				pr_err("File %s has bad mode 0%o (expect 0%o)\n"
+				       "File r/w/x checks can be skipped with the --skip-file-rwx-check option\n",
+				       rfi->path, (int)curr_mode, saved_mode);
+				goto err;
+			}
 		}
 
 		/*

criu/include/cr_options.h

@@ -179,6 +179,7 @@ struct cr_options {
 	bool lazy_pages;
 	char *work_dir;
 	int network_lock_method;
+	int skip_file_rwx_check;
 
 	/*
 	 * When we scheduler for removal some functionality we first

images/rpc.proto

@@ -138,6 +138,7 @@ message criu_opts {
 	optional string			lsm_mount_context	= 63;
 	optional criu_network_lock_method	network_lock		= 64 [default = IPTABLES];
 	optional bool			mntns_compat_mode	= 65;
+	optional bool			skip_file_rwx_check	= 66;
 /*	optional bool			check_mounts		= 128;	*/
 }
 

lib/c/criu.c

@@ -555,6 +555,17 @@ void criu_set_shell_job(bool shell_job)
 	criu_local_set_shell_job(global_opts, shell_job);
 }
 
+void criu_local_set_skip_file_rwx_check(criu_opts *opts, bool skip_file_rwx_check)
+{
+	opts->rpc->has_skip_file_rwx_check = true;
+	opts->rpc->skip_file_rwx_check = skip_file_rwx_check;
+}
+
+void criu_set_skip_file_rwx_check(bool skip_file_rwx_check)
+{
+	criu_local_set_skip_file_rwx_check(global_opts, skip_file_rwx_check);
+}
+
 void criu_local_set_orphan_pts_master(criu_opts *opts, bool orphan_pts_master)
 {
 	opts->rpc->has_orphan_pts_master = true;

lib/c/criu.h

@@ -78,6 +78,7 @@ void criu_set_tcp_close(bool tcp_close);
 void criu_set_weak_sysctls(bool val);
 void criu_set_evasive_devices(bool evasive_devices);
 void criu_set_shell_job(bool shell_job);
+void criu_set_skip_file_rwx_check(bool skip_file_rwx_check);
 void criu_set_orphan_pts_master(bool orphan_pts_master);
 void criu_set_file_locks(bool file_locks);
 void criu_set_track_mem(bool track_mem);
@@ -238,6 +239,7 @@ void criu_local_set_tcp_close(criu_opts *opts, bool tcp_close);
 void criu_local_set_weak_sysctls(criu_opts *opts, bool val);
 void criu_local_set_evasive_devices(criu_opts *opts, bool evasive_devices);
 void criu_local_set_shell_job(criu_opts *opts, bool shell_job);
+void criu_local_set_skip_file_rwx_check(criu_opts *opts, bool skip_file_rwx_check);
 void criu_local_set_orphan_pts_master(criu_opts *opts, bool orphan_pts_master);
 void criu_local_set_file_locks(criu_opts *opts, bool file_locks);
 void criu_local_set_track_mem(criu_opts *opts, bool track_mem);