linux-kernel - Re: [RFC PATCH] initramfs: correctly handle space in path on cpio list generation

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Message-ID: <20260210223431.6bf63673.ddiss@suse.de>
Date: Tue, 10 Feb 2026 22:34:31 +1100
From: David Disseldorp <ddiss@...e.de>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nsc@...nel.org>,
 Dmitry Safonov <0x7f454c46@...il.com>, linux-kbuild@...r.kernel.org,
 linux-kernel@...r.kernel.org, "linux-fsdevel@...r.kernel.org"
 <linux-fsdevel@...r.kernel.org>
Subject: Re: [RFC PATCH] initramfs: correctly handle space in path on cpio
 list generation

[cc'ing fsdevel]

On Mon,  9 Feb 2026 16:37:58 +0100, Christian Marangi wrote:

> The current gen_initramfs.sh and gen_init_cpio.c tools doesn't correctly
> handle path or filename with space in it. Although highly discouraged,

"highly discouraged" isn't really appropriate here; the kernel generally
doesn't care whether or not a filename carries whitespace.
The limitation here is specifically the gen_init_cpio manifest format,
which is strictly space-separated.

> Linux also supports filename or path with whiespace and currently this
> will produce error on generating and parsing the cpio_list file as the
> pattern won't match the expected variables order. (with gid or mode
> parsed as string)
> 
> This was notice when creating an initramfs with including the ALSA test
> files and configuration that have whitespace in both some .conf and even
> some symbolic links.
> 
> Example error:

The error messages don't really add any value here.
<snip>

> To correctly handle this problem, rework the gen_initramfs.sh and
> gen_init_cpio.c to guard all the path with "" to handle all kind of
> whitespace for filename/path.
> 
> The default_cpio_list is also updated to follow this new pattern.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> ---
>  usr/default_cpio_list |  6 +++---
>  usr/gen_init_cpio.c   | 10 +++++-----
>  usr/gen_initramfs.sh  | 27 +++++++++++++++++++--------
>  3 files changed, 27 insertions(+), 16 deletions(-)
> 
> diff --git a/usr/default_cpio_list b/usr/default_cpio_list
> index 37b3864066e8..d4a66b4aa7f7 100644
> --- a/usr/default_cpio_list
> +++ b/usr/default_cpio_list
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0-only
>  # This is a very simple, default initramfs
>  
> -dir /dev 0755 0 0
> -nod /dev/console 0600 0 0 c 5 1
> -dir /root 0700 0 0
> +dir "/dev" 0755 0 0
> +nod "/dev/console" 0600 0 0 c 5 1
> +dir "/root" 0700 0 0
> diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
> index b7296edc6626..ca5950998841 100644
> --- a/usr/gen_init_cpio.c
> +++ b/usr/gen_init_cpio.c
> @@ -166,7 +166,7 @@ static int cpio_mkslink_line(const char *line)
>  	int gid;
>  	int rc = -1;
>  
> -	if (5 != sscanf(line, "%" str(PATH_MAX) "s %" str(PATH_MAX) "s %o %d %d", name, target, &mode, &uid, &gid)) {
> +	if (5 != sscanf(line, "\"%" str(PATH_MAX) "[^\"]\" \"%" str(PATH_MAX) "[^\"]\" %o %d %d", name, target, &mode, &uid, &gid)) {

This breaks parsing of existing manifest files, so is unacceptable
IMO. If we really want to go down the route of having gen_init_cpio
support space-separated paths, then perhaps a new --field-separator
parameter might make sense. For your specific workload it seems that
simply using an external cpio archiver with space support (e.g. GNU
cpio --null) would make sense. Did you consider going down that
path?

Thanks, David