[PATCH] dm: verity: Add support for emitting uevents on dm-verity errors.

[Geremy Condra]

With this change and config option, dm-verity errors
will cause uevents to be sent to userspace, notifying
it that an error has occurred and potentially
triggering recovery actions.

Signed-off-by: Geremy Condra <gcondra@xxxxxxxxxx>
Change-Id: If3d9c00770d1a640faa0d42318cce675da40c000
---
 drivers/md/Kconfig     |  6 ++++++
 drivers/md/dm-uevent.c | 40 ++++++++++++++++++++++++++++++++++++++++
 drivers/md/dm-uevent.h | 12 ++++++++++--
 drivers/md/dm-verity.c | 28 ++++++++++++++++++++++++++++
 4 files changed, 84 insertions(+), 2 deletions(-)

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 10f122a..fab9c32 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -390,4 +390,10 @@ config DM_VERITY
 
 	  If unsure, say N.
 
+config DM_VERITY_ERROR_NOTIFY
+	tristate "Notify userspace of verity errors through uevents"
+	depends on DM_VERITY && DM_UEVENT
+	---help---
+	  This option instructs dm-verity to send uevents on error.
+
 endif # MD
diff --git a/drivers/md/dm-uevent.c b/drivers/md/dm-uevent.c
index 8efe033..17a6662 100644
--- a/drivers/md/dm-uevent.c
+++ b/drivers/md/dm-uevent.c
@@ -36,6 +36,8 @@ static const struct {
 } _dm_uevent_type_names[] = {
 	{DM_UEVENT_PATH_FAILED, KOBJ_CHANGE, "PATH_FAILED"},
 	{DM_UEVENT_PATH_REINSTATED, KOBJ_CHANGE, "PATH_REINSTATED"},
+	{DM_UEVENT_VERITY_DATA_ERROR, KOBJ_CHANGE, "VERITY_DATA_ERROR"},
+	{DM_UEVENT_VERITY_HASH_ERROR, KOBJ_CHANGE, "VERITY_HASH_ERROR"},
 };
 
 static struct kmem_cache *_dm_event_cache;
@@ -202,6 +204,44 @@ void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
 }
 EXPORT_SYMBOL_GPL(dm_path_uevent);
 
+void dm_send_verity_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
+						unsigned long long block_nr)
+{
+	struct mapped_device *md = dm_table_get_md(ti->table);
+	struct dm_uevent *event = dm_uevent_alloc(md);
+	struct gendisk *disk = dm_disk(md);
+
+	if (!event) {
+		DMERR("%s: dm_uevent_alloc() failed", __func__);
+		return;
+	}
+
+	if (event_type >= ARRAY_SIZE(_dm_uevent_type_names)) {
+		DMERR("%s: Invalid event_type %d", __func__, event_type);
+		goto out;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_VERITY_BLOCK_NR=%llu", block_nr)) {
+		DMERR("%s: add_uevent_var() for DM_VERITY_BLOCK failed", __func__);
+		goto out;
+	}
+
+	if (add_uevent_var(&event->ku_env, "DM_ACTION=%s",
+			_dm_uevent_type_names[event_type].name)) {
+		DMERR("%s: add_uevent_var() for DM_ACTION failed", __func__);
+		goto out;
+	}
+
+	if (kobject_uevent_env(&disk_to_dev(disk)->kobj, event_type,
+				event->ku_env.envp)) {
+		DMERR("%s: kobject_uevent_env failed", __func__);
+	}
+
+out:
+	dm_uevent_free(event);
+}
+EXPORT_SYMBOL_GPL(dm_send_verity_uevent);
+
 int dm_uevent_init(void)
 {
 	_dm_event_cache = KMEM_CACHE(dm_uevent, 0);
diff --git a/drivers/md/dm-uevent.h b/drivers/md/dm-uevent.h
index 2eccc8b..1c59dba 100644
--- a/drivers/md/dm-uevent.h
+++ b/drivers/md/dm-uevent.h
@@ -24,6 +24,8 @@
 enum dm_uevent_type {
 	DM_UEVENT_PATH_FAILED,
 	DM_UEVENT_PATH_REINSTATED,
+	DM_UEVENT_VERITY_DATA_ERROR,
+	DM_UEVENT_VERITY_HASH_ERROR,
 };
 
 #ifdef CONFIG_DM_UEVENT
@@ -34,7 +36,9 @@ extern void dm_send_uevents(struct list_head *events, struct kobject *kobj);
 extern void dm_path_uevent(enum dm_uevent_type event_type,
 			   struct dm_target *ti, const char *path,
 			   unsigned nr_valid_paths);
-
+extern void dm_send_verity_uevent(enum dm_uevent_type event_type,
+					struct dm_target *ti,
+					unsigned long long block_nr);
 #else
 
 static inline int dm_uevent_init(void)
@@ -53,7 +57,11 @@ static inline void dm_path_uevent(enum dm_uevent_type event_type,
 				  unsigned nr_valid_paths)
 {
 }
-
+static inline void dm_send_verity_uevent(enum dm_uevent_type event_type,
+					struct dm_target *ti,
+					unsigned long long block_nr)
+{
+}
 #endif	/* CONFIG_DM_UEVENT */
 
 #endif	/* DM_UEVENT_H */
diff --git a/drivers/md/dm-verity.c b/drivers/md/dm-verity.c
index 68bf5c3..c9c9ecc 100644
--- a/drivers/md/dm-verity.c
+++ b/drivers/md/dm-verity.c
@@ -20,6 +20,8 @@
 #include <linux/device-mapper.h>
 #include <crypto/hash.h>
 
+#include "dm-uevent.h"
+
 #define DM_MSG_PREFIX			"verity"
 
 #define DM_VERITY_IO_VEC_INLINE		16
@@ -137,6 +139,30 @@ static void dm_bufio_alloc_callback(struct dm_buffer *buf)
 }
 
 /*
+ * Trigger userspace data corruption handler.
+ */
+#ifdef CONFIG_DM_VERITY_ERROR_NOTIFY
+static void verity_data_error(struct dm_verity *v, unsigned long long block_nr)
+{
+	dm_send_verity_uevent(DM_UEVENT_VERITY_DATA_ERROR, v->ti, block_nr);
+}
+
+static void verity_hash_error(struct dm_verity *v, unsigned long long block_nr)
+{
+	dm_send_verity_uevent(DM_UEVENT_VERITY_HASH_ERROR, v->ti, block_nr);
+}
+#else
+static inline void verity_data_error(struct dm_verity *v,
+					unsigned long long block_nr)
+{
+}
+static inline void verity_hash_error(struct dm_verity *v,
+					unsigned long long block_nr)
+{
+}
+#endif
+
+/*
  * Translate input sector number to the sector number on the target device.
  */
 static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
@@ -255,6 +281,7 @@ static int verity_verify_level(struct dm_verity_io *io, sector_t block,
 				(unsigned long long)hash_block);
 			v->hash_failed = 1;
 			r = -EIO;
+			verity_hash_error(v, (unsigned long long)hash_block);
 			goto release_ret_r;
 		} else
 			aux->hash_verified = 1;
@@ -375,6 +402,7 @@ test_block_hash:
 			DMERR_LIMIT("data block %llu is corrupted",
 				(unsigned long long)(io->block + b));
 			v->hash_failed = 1;
+			verity_data_error(v, (unsigned long long)(io->block + b));
 			return -EIO;
 		}
 	}
-- 
1.8.3

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