mtd: improve check for TRX header being already fixed

First of all lengths should be compared after checking all blocks for
being good/bad. It's because requested length may differ from a final
one if there were some bad blocks.

Secondly it makes sense to also compare crc32 since we already have a
new one calculated.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

package/system/mtd/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=mtd
-PKG_RELEASE:=22
+PKG_RELEASE:=23
 
 PKG_BUILD_DIR := $(KERNEL_BUILD_DIR)/$(PKG_NAME)
 STAMP_PREPARED := $(STAMP_PREPARED)_$(call confvar,CONFIG_MTD_REDBOOT_PARTS)

package/system/mtd/src/trx.c

@@ -207,13 +207,6 @@ mtd_fixtrx(const char *mtd, size_t offset, size_t data_size)
 		exit(1);
 	}
 
-	if (trx->len == STORE32_LE(data_size + TRX_CRC32_DATA_OFFSET)) {
-		if (quiet < 2)
-			fprintf(stderr, "Header already fixed, exiting\n");
-		close(fd);
-		return 0;
-	}
-
 	buf = malloc(data_size);
 	if (!buf) {
 		perror("malloc");
@@ -243,6 +236,14 @@ mtd_fixtrx(const char *mtd, size_t offset, size_t data_size)
 	}
 	data_size = to - buf;
 
+	if (trx->len == STORE32_LE(data_size + TRX_CRC32_DATA_OFFSET) &&
+	    trx->crc32 == STORE32_LE(crc32buf(buf, data_size))) {
+		if (quiet < 2)
+			fprintf(stderr, "Header already fixed, exiting\n");
+		close(fd);
+		return 0;
+	}
+
 	trx->len = STORE32_LE(data_size + offsetof(struct trx_header, flag_version));
 
 	trx->crc32 = STORE32_LE(crc32buf(buf, data_size));