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@gmail.com>

diff --git a/package/base-files/files/lib/upgrade/nand.sh b/package/base-files/files/lib/upgrade/nand.sh
index b5c982b27227fcec709048c4b0155364d71f2f30..f927c066dab769230c4d3ca655dca2d01e1d8a34 100644 (file)
--- 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
 }