[U-Boot] [PATCH v2 1/7] fs: ext4: do not allow writes if metadata checksum is active

[Tom Rini]

On Fri, Feb 01, 2019 at 03:33:34PM +0100, Jean-Jacques Hiblot wrote:

> u-boot does not supports updating the metadata chacksums
> 
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot at ti.com>
> 
> ---
> 
> Changes in v2:
> - Prevent write access if metadata checksum is enabled
> 
>  fs/ext4/ext4_write.c | 12 ++++++++++--
>  include/ext4fs.h     |  1 +
>  2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/ext4_write.c b/fs/ext4/ext4_write.c
> index a7f543f7df..1de29236f0 100644
> --- a/fs/ext4/ext4_write.c
> +++ b/fs/ext4/ext4_write.c
> @@ -858,12 +858,19 @@ int ext4fs_write(const char *fname, unsigned char *buffer,
>  
>  	g_parent_inode = zalloc(fs->inodesz);
>  	if (!g_parent_inode)
> -		goto fail;
> +		goto fail_ext4fs_init;
>  
>  	if (ext4fs_init() != 0) {
>  		printf("error in File System init\n");
> -		return -1;
> +		goto fail_ext4fs_init;
> +	}
> +
> +	if (le32_to_cpu(fs->sb->feature_ro_compat) &
> +		EXT4_FEATURE_RO_COMPAT_METADATA_CSUM) {
> +		printf("u-boot doesn't support updating the metadata checksums yet\n");
> +		goto fail;
>  	}
> +
>  	inodes_per_block = fs->blksz / fs->inodesz;
>  	parent_inodeno = ext4fs_get_parent_inode_num(fname, filename, F_FILE);
>  	if (parent_inodeno == -1)

I'm following up to myself on this one as, Ugh.  To repeat myself from a
while back:
commit 6f94ab6656ceffb3f2a972c8de4c554502b6f2b7
Author: Tom Rini <trini at konsulko.com>
Date:   Fri Jul 22 17:59:11 2016 -0400

    ext4: Refuse to mount filesystems with 64bit feature set
    
    With e2fsprogs after 1.43 the 64bit and metadata_csum features are
    enabled by default.  The metadata_csum feature changes how
    ext4_group_desc->bg_checksum is calculated, which would break write
    support.  The 64bit feature however introduces changes such that it
    cannot be read by implementations that do not support it.  Since we do
    not support this, we must not mount it.
    
    Cc: Stephen Warren <swarren at nvidia.com>
    Cc: Simon Glass <sjg at chromium.org>
    Cc: Lukasz Majewski <l.majewski at samsung.com>
    Cc: Stefan Roese <sr at denx.de>
    Reported-by: Andrew Bradford <andrew.bradford at kodakalaris.com>
    Signed-off-by: Tom Rini <trini at konsulko.com>

Which means that starting way back then I should have also done
something to say we cannot write to these new images either.  It's good
and important to finally catch this failure now.  I suspect it's however
going to start to be an unexpected problem.  Have you any idea how much
work would go in to supporting the metadata_csum feature?  Thanks again!

-- 
Tom
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