[PATCH] dm-verity: increase sprintf buffer size

The prefix "DM_VERITY_ERR_BLOCK_NR" is 22 chars. Add '=', one digit for
type, ',', up to 20 digits for a u64 block number, and a NUL terminator:
that's 46 bytes. The buffer is 42 bytes. For block numbers >= 16 decimal
digits (devices larger than ~16 EB with 4K blocks), snprintf silently
truncates the uevent environment variable.

Signed-off-by: Mikulas Patocka <[email protected]>
Assisted-by: Claude:claude-opus-4.6
Fixes: 65ff5b7ddf05 ("dm verity: add error handling modes for corrupted blocks")
Cc: [email protected]

---
 drivers/md/dm-verity-target.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/drivers/md/dm-verity-target.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-verity-target.c	2026-07-01 13:31:00.000000000 +0200
+++ linux-2.6/drivers/md/dm-verity-target.c	2026-07-01 18:16:12.000000000 +0200
@@ -26,7 +26,7 @@
 
 #define DM_MSG_PREFIX			"verity"
 
-#define DM_VERITY_ENV_LENGTH		42
+#define DM_VERITY_ENV_LENGTH		46
 #define DM_VERITY_ENV_VAR_NAME		"DM_VERITY_ERR_BLOCK_NR"
 
 #define DM_VERITY_DEFAULT_PREFETCH_SIZE	262144