[PATCH v3 07/10] crash_dump: Improve readability of config_keys_restore_store

[Coiby Xu <coiby.xu@gmail.com>]

config_keys_restore_store currently doesn't validate the user input
before restoring dm-crypt keys. Although it's not necessary for the case
of vmcore dumping, it's better to do it for the sake of consistency and
code readability. Also check the return code of
restore_dm_crypt_keys_to_thread_keyring.

Fixes: 62f17d9df692 ("crash_dump: retrieve dm crypt keys in kdump kernel")
Signed-off-by: Coiby Xu <coiby.xu@gmail.com>
---
 kernel/crash_dump_dm_crypt.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
index 3ee01996778f..1f4549956824 100644
--- a/kernel/crash_dump_dm_crypt.c
+++ b/kernel/crash_dump_dm_crypt.c
@@ -370,12 +370,19 @@ static ssize_t config_keys_restore_show(struct config_item *item, char *page)
 static ssize_t config_keys_restore_store(struct config_item *item,
 					  const char *page, size_t count)
 {
-	if (!restore)
-		restore_dm_crypt_keys_to_thread_keyring();
+	bool val;
 
-	if (kstrtobool(page, &restore))
+	if (kstrtobool(page, &val))
 		return -EINVAL;
 
+	if (val) {
+		if (restore) {
+			pr_warn("dm-crypt keys already restored!\n");
+			return count;
+		} else if (!restore_dm_crypt_keys_to_thread_keyring())
+			restore = true;
+	}
+
 	return count;
 }
 
-- 
2.55.0