libfdisk: properly implement read-only mode

Don't use fallback to read-only mode in fdisk_context_assign_device(),
it's application responsibility open the device in the right mode.

The commands fdisk and cfdisk check (and report) read-only mode now.

Reported-by: Maciej Małecki <me@mmalecki.com>
Signed-off-by: Karel Zak <kzak@redhat.com>

7 files changed, 45 insertions, 12 deletions

diff --git a/disk-utils/cfdisk.c b/disk-utils/cfdisk.c
index 6a07ced25..651c45b85 100644
--- a/disk-utils/cfdisk.c
+++ b/disk-utils/cfdisk.c
@@ -1525,6 +1525,10 @@ static int main_menu_ignore_keys(struct cfdisk *cf, char *ignore,
 		    !fdisk_is_disklabel(cf->cxt, SGI))
 			ignore[i++] = 'b';
 	}
+
+
+	if (fdisk_context_is_readonly(cf->cxt))
+		ignore[i++] = 'W';
 	return i;
 }
 
@@ -1643,7 +1647,14 @@ static int main_menu_action(struct cfdisk *cf, int key)
 	case 'W': /* Write */
 	{
 		char buf[64] = { 0 };
-		int rc = ui_get_string(cf,
+		int rc;
+
+		if (fdisk_context_is_readonly(cf->cxt)) {
+			ui_warnx(_("Device open in read-only mode"));
+			break;
+		}
+
+		rc = ui_get_string(cf,
 			  _("Are you sure you want to write the partition "
 			    "table to disk? "),
 			  _("Type \"yes\" or \"no\" or press ESC to left dialog."),
@@ -1709,6 +1720,9 @@ static int ui_run(struct cfdisk *cf)
 	if (rc)
 		return rc;
 
+	if (fdisk_context_is_readonly(cf->cxt))
+		ui_warnx(_("Device open in read-only mode."));
+
 	do {
 		int rc = 0, key = getch();
 
@@ -1835,7 +1849,10 @@ int main(int argc, char *argv[])
 	if (optind == argc)
 		usage(stderr);
 
-	if (fdisk_context_assign_device(cf->cxt, argv[optind], 0) != 0)
+	rc = fdisk_context_assign_device(cf->cxt, argv[optind], 0);
+	if (rc == -EACCES)
+		rc = fdisk_context_assign_device(cf->cxt, argv[optind], 1);
+	if (rc != 0)
 		err(EXIT_FAILURE, _("cannot open %s"), argv[optind]);
 
 	/* Don't use err(), warn() from this point */
diff --git a/disk-utils/fdisk-menu.c b/disk-utils/fdisk-menu.c
index 822761568..bdaa73475 100644
--- a/disk-utils/fdisk-menu.c
+++ b/disk-utils/fdisk-menu.c
@@ -447,6 +447,10 @@ static int generic_menu_cb(struct fdisk_context **cxt0,
 		list_disklabel(cxt);
 		break;
 	case 'w':
+		if (fdisk_context_is_readonly(cxt)) {
+			fdisk_warnx(cxt, _("Device open in read-only mode."));
+			break;
+		}
 		rc = fdisk_write_disklabel(cxt);
 		if (rc)
 			err(EXIT_FAILURE, _("failed to write disklabel"));
diff --git a/disk-utils/fdisk.c b/disk-utils/fdisk.c
index fa7f248cc..bfe3fe3b5 100644
--- a/disk-utils/fdisk.c
+++ b/disk-utils/fdisk.c
@@ -778,7 +778,7 @@ enum {
 
 int main(int argc, char **argv)
 {
-	int i, c, act = ACT_FDISK;
+	int rc, i, c, act = ACT_FDISK;
 	int colormode = UL_COLORMODE_UNDEF;
 	struct fdisk_context *cxt;
 
@@ -920,7 +920,13 @@ int main(int argc, char **argv)
 		fdisk_info(cxt, _("Changes will remain in memory only, until you decide to write them.\n"
 				  "Be careful before using the write command.\n"));
 
-		if (fdisk_context_assign_device(cxt, argv[optind], 0) != 0)
+		rc = fdisk_context_assign_device(cxt, argv[optind], 0);
+		if (rc == -EACCES) {
+			rc = fdisk_context_assign_device(cxt, argv[optind], 1);
+			if (rc == 0)
+				fdisk_warnx(cxt, _("Device open in read-only mode."));
+		}
+		if (rc)
 			err(EXIT_FAILURE, _("cannot open %s"), argv[optind]);
 
 		fflush(stdout);
diff --git a/libfdisk/src/context.c b/libfdisk/src/context.c
index 7d7b0c668..ec0b6d84f 100644
--- a/libfdisk/src/context.c
+++ b/libfdisk/src/context.c
@@ -260,12 +260,11 @@ int fdisk_context_assign_device(struct fdisk_context *cxt,
 
 	reset_context(cxt);
 
-	if (readonly == 1 || (fd = open(fname, O_RDWR|O_CLOEXEC)) < 0) {
-		if ((fd = open(fname, O_RDONLY|O_CLOEXEC)) < 0)
-			return -errno;
-		readonly = 1;
-	}
+	fd = open(fname, (readonly ? O_RDONLY : O_RDWR ) | O_CLOEXEC);
+	if (fd < 0)
+		return -errno;
 
+	cxt->readonly = readonly;
 	cxt->dev_fd = fd;
 	cxt->dev_path = strdup(fname);
 	if (!cxt->dev_path)
@@ -315,6 +314,12 @@ int fdisk_context_deassign_device(struct fdisk_context *cxt)
 	return 0;
 }
 
+int fdisk_context_is_readonly(struct fdisk_context *cxt)
+{
+	assert(cxt);
+	return cxt->readonly;
+}
+
 /**
  * fdisk_free_context:
  * @cxt: fdisk context
diff --git a/libfdisk/src/fdiskP.h b/libfdisk/src/fdiskP.h
index b5880df70..cb3c2b27c 100644
--- a/libfdisk/src/fdiskP.h
+++ b/libfdisk/src/fdiskP.h
@@ -346,7 +346,8 @@ struct fdisk_context {
 	unsigned long sector_size;	/* logical size */
 	unsigned long alignment_offset;
 
-	unsigned int display_in_cyl_units : 1,	/* for obscure labels */
+	unsigned int readonly : 1,		/* don't write to the device */
+		     display_in_cyl_units : 1,	/* for obscure labels */
 		     display_details : 1,	/* expert display mode */
 		     listonly : 1;		/* list partition, nothing else */
 
diff --git a/libfdisk/src/label.c b/libfdisk/src/label.c
index 360089972..9c6fcc5b3 100644
--- a/libfdisk/src/label.c
+++ b/libfdisk/src/label.c
@@ -75,11 +75,10 @@ int fdisk_dev_is_disklabel(struct fdisk_context *cxt, enum fdisk_labeltype l)
  */
 int fdisk_write_disklabel(struct fdisk_context *cxt)
 {
-	if (!cxt || !cxt->label)
+	if (!cxt || !cxt->label || cxt->readonly)
 		return -EINVAL;
 	if (!cxt->label->op->write)
 		return -ENOSYS;
-
 	return cxt->label->op->write(cxt);
 }
 
diff --git a/libfdisk/src/libfdisk.h b/libfdisk/src/libfdisk.h
index 3a173e390..ed48da793 100644
--- a/libfdisk/src/libfdisk.h
+++ b/libfdisk/src/libfdisk.h
@@ -78,6 +78,7 @@ extern int fdisk_context_set_ask(struct fdisk_context *cxt,
 			int (*ask_cb)(struct fdisk_context *, struct fdisk_ask *, void *),
 			void *data);
 
+extern int fdisk_context_is_readonly(struct fdisk_context *cxt);
 extern int fdisk_context_assign_device(struct fdisk_context *cxt,
 				const char *fname, int readonly);
 extern int fdisk_context_deassign_device(struct fdisk_context *cxt);