dm verity: add "panic_on_corruption" error handling mode

Samsung smart phones may need the ability to panic on corruption.  Not
all devices provide the bootloader support needed to use the existing
"restart_on_corruption" mode.  Additional details for why Samsung needs
this new mode can be found here:
https://www.redhat.com/archives/dm-devel/2020-June/msg00235.htmlSigned-off-by: jhs2.lee <jhs2.lee@samsung.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Documentation/admin-guide/device-mapper/verity.rst

@@ -83,6 +83,10 @@ restart_on_corruption
     not compatible with ignore_corruption and requires user space support to
     avoid restart loops.
 
+panic_on_corruption
+    Panic the device when a corrupted block is discovered. This option is
+    not compatible with ignore_corruption and restart_on_corruption.
+
 ignore_zero_blocks
     Do not verify blocks that are expected to contain zeroes and always return
     zeroes instead. This may be useful if the partition contains unused blocks

drivers/md/dm-verity-target.c

@@ -30,6 +30,7 @@
 
 #define DM_VERITY_OPT_LOGGING		"ignore_corruption"
 #define DM_VERITY_OPT_RESTART		"restart_on_corruption"
+#define DM_VERITY_OPT_PANIC		"panic_on_corruption"
 #define DM_VERITY_OPT_IGN_ZEROES	"ignore_zero_blocks"
 #define DM_VERITY_OPT_AT_MOST_ONCE	"check_at_most_once"
 
@@ -254,6 +255,9 @@ static int verity_handle_err(struct dm_verity *v, enum verity_block_type type,
 	if (v->mode == DM_VERITY_MODE_RESTART)
 		kernel_restart("dm-verity device corrupted");
 
+	if (v->mode == DM_VERITY_MODE_PANIC)
+		panic("dm-verity device corrupted");
+
 	return 1;
 }
 
@@ -742,6 +746,9 @@ static void verity_status(struct dm_target *ti, status_type_t type,
 			case DM_VERITY_MODE_RESTART:
 				DMEMIT(DM_VERITY_OPT_RESTART);
 				break;
+			case DM_VERITY_MODE_PANIC:
+				DMEMIT(DM_VERITY_OPT_PANIC);
+				break;
 			default:
 				BUG();
 			}
@@ -907,6 +914,10 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
 			v->mode = DM_VERITY_MODE_RESTART;
 			continue;
 
+		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_PANIC)) {
+			v->mode = DM_VERITY_MODE_PANIC;
+			continue;
+
 		} else if (!strcasecmp(arg_name, DM_VERITY_OPT_IGN_ZEROES)) {
 			r = verity_alloc_zero_digest(v);
 			if (r) {
@@ -1221,7 +1232,7 @@ static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 
 static struct target_type verity_target = {
 	.name		= "verity",
-	.version	= {1, 6, 0},
+	.version	= {1, 7, 0},
 	.module		= THIS_MODULE,
 	.ctr		= verity_ctr,
 	.dtr		= verity_dtr,

drivers/md/dm-verity.h

@@ -20,7 +20,8 @@
 enum verity_mode {
 	DM_VERITY_MODE_EIO,
 	DM_VERITY_MODE_LOGGING,
-	DM_VERITY_MODE_RESTART
+	DM_VERITY_MODE_RESTART,
+	DM_VERITY_MODE_PANIC
 };
 
 enum verity_block_type {