[openwrt/openwrt] base-files: safer sysupgrade for kernel-in-UBI devices

[LEDE Commits]

dangole pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/073dc450b5ca91cfffd9097f0e3900dd390be399

commit 073dc450b5ca91cfffd9097f0e3900dd390be399
Author: Rodrigo Balerdi <lanchon at gmail.com>
AuthorDate: Fri Apr 15 00:59:49 2022 -0300

    base-files: safer sysupgrade for kernel-in-UBI devices
    
    Ensure that the kernel CRC is invalidated while rootfs is being updated.
    This allows the bootloader to detect an interrupted sysupgrade and fall
    back to an alternate booting method, instead of just going ahead with
    normal boot and effectively bricking the device.
    
    Possible fallbacks include a recovery initramfs partition or UBI volume
    and TFTP. See here for an example U-Boot configuration with fallbacks:
    https://shorturl.at/befsA (https://github.com/Lanchon/openwrt-tr4400-v2/
    blob/e7d707d6bd7839fbd0b8d0bd180fce451df77e47/install-recovery.sh#L52-L63)
    
    Signed-off-by: Rodrigo Balerdi <lanchon at gmail.com>
---
 package/base-files/files/lib/upgrade/nand.sh | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/package/base-files/files/lib/upgrade/nand.sh b/package/base-files/files/lib/upgrade/nand.sh
index b5c982b272..f927c066da 100644
--- a/package/base-files/files/lib/upgrade/nand.sh
+++ b/package/base-files/files/lib/upgrade/nand.sh
@@ -288,7 +288,7 @@ nand_upgrade_tar() {
 	local board_dir=$(tar tf "$tar_file" | grep -m 1 '^sysupgrade-.*/$')
 	board_dir=${board_dir%/}
 
-	kernel_length=$( (tar xf "$tar_file" ${board_dir}/kernel -O | wc -c) 2> /dev/null)
+	local kernel_length=$( (tar xf "$tar_file" ${board_dir}/kernel -O | wc -c) 2> /dev/null)
 	local has_rootfs=0
 	local rootfs_length
 	local rootfs_type
@@ -311,17 +311,17 @@ nand_upgrade_tar() {
 	nand_upgrade_prepare_ubi "$rootfs_length" "$rootfs_type" "${has_kernel:+$kernel_length}" "$has_env"
 
 	local ubidev="$( nand_find_ubi "$CI_UBIPART" )"
-	[ "$has_kernel" = "1" ] && {
-		local kern_ubivol="$( nand_find_volume $ubidev $CI_KERNPART )"
-		tar xf "$tar_file" ${board_dir}/kernel -O | \
-			ubiupdatevol /dev/$kern_ubivol -s $kernel_length -
-	}
-
 	[ "$has_rootfs" = "1" ] && {
 		local root_ubivol="$( nand_find_volume $ubidev $CI_ROOTPART )"
 		tar xf "$tar_file" ${board_dir}/root -O | \
 			ubiupdatevol /dev/$root_ubivol -s $rootfs_length -
 	}
+
+	[ "$has_kernel" = "1" ] && {
+		local kern_ubivol="$( nand_find_volume $ubidev $CI_KERNPART )"
+		tar xf "$tar_file" ${board_dir}/kernel -O | \
+			ubiupdatevol /dev/$kern_ubivol -s $kernel_length -
+	}
 	nand_do_upgrade_success
 }