[PATCH] base-files: fix sysupgrade with ubi and kernel sharing partition

[Lanchon]

hi,

sorry for the delay. I didn't expect that kind of sharing.

your fix is not enough: when later the partition is written, it is via 
'mtd -n write' which expects an erased partition.

i will do a PR ASAP to fix this by invalidating the start of the kernel 
partition instead of erasing it, this is enough to invalidate the kernel 
CRC.

thanks!



On 4/29/22 11:37, Bjørn Mork wrote:
> Commit ecbcc0b59551 bricks devices where a ubi rootfs and a raw
> kernel shares the same mtd partition.
>
> This is the case for the ZyXEL NR7101 for example.  The OEM bootloader
> has no UBI support.  OpenWrt splits the "Kernel" mtd partition in a raw
> kernel part used by the bootloader and a UBI part used for the OpenWrt
> rootfs and rootfs_data.  Running mtd erase on this partition during
> during upgrade erases the UBI part and results in a soft brick.
>
> Fixes: ecbcc0b59551 ("base-files: safer sysupgrade.tar for kernel-out-of-UBI")
> Signed-off-by: Bjørn Mork <bjorn at mork.no>
> ---
>
> I'm not sure what the proper fix for this is.  I believe the intended
> functionality of commit ecbcc0b59551 should be re-implemented somehow.
>
> I guess the real bug might be the dual usage of this partition?  But
> I'm pretty sure I found that as an example in some other device,
> without being able to point it out now.
>
> But I believe we need this immediate fix in any case, since this is a
> bricking regression.
>
>
>   package/base-files/files/lib/upgrade/nand.sh | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/package/base-files/files/lib/upgrade/nand.sh b/package/base-files/files/lib/upgrade/nand.sh
> index 5ecdb0ff2363..5e5607d35cd8 100644
> --- a/package/base-files/files/lib/upgrade/nand.sh
> +++ b/package/base-files/files/lib/upgrade/nand.sh
> @@ -305,7 +305,7 @@ nand_upgrade_tar() {
>   	local ubi_kernel_length
>   	if [ "$kernel_length" ]; then
>   		if [ "$kernel_mtd" ]; then
> -			mtd erase "$CI_KERNPART"
> +			: # mtd erase "$CI_KERNPART"
>   		else
>   			ubi_kernel_length="$kernel_length"
>   		fi