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

[Christian Marangi]

On Wed, Feb 11, 2026 at 11:43:10AM +1100, David Disseldorp wrote:
> On Tue, 10 Feb 2026 18:37:44 +0100, Christian Marangi wrote:
> ...
> > > > 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?
> > >   
> > 
> > This is mostly why this is posted as RFC. I honestly wants to fix this in the
> > linux tool instead of using external tools.
> > 
> > So is there an actual use of manually passing the cpio list instead of
> > generating one with the script? (just asking not saying that there isn't one)
> 
> Absolutely. As a simple example, consider an unprivileged user wishing
> to add a device node to their initramfs image. A manifest entry (as
> opposed to staging area mknod=EPERM) is ideal for this.
> 
> > One case I have (the scenario here is OpenWrt) is when a base cpio_list is
> > provided and then stuff is appended to it.
> > 
> > In such case yes there is a problem since the format changed.
> > 
> > My solution to this would be introduce new type that will have the new pattern.
> > This way we can keep support for the old list and still handle whitespace files.
> > 
> > An idea might be to have the file type with capital letter to differenciate with
> > the old one.
> > 
> > Something like 
> > 
> > FILE "path" "location" ...
> > SLINK "name" "target" ...
> > NODE ...
> > 
> > What do you think?
> 
> Introducing a new type to handle space-containing filenames isn't a bad
> idea, but using capital letters to signify the API change is confusing.
>

The problem of a new type is that other tool might not support that but no idea
if it would be really that relevant. After all it's all intermediate file to
generate the final cpio.
 
> > The option of --field-separator might also work but it might complicate stuff in
> > the .c tool as a more ""manual"" tokenizer will be needed than the simple
> > implementation currently present.
> 
> What happens when someone wants support for filenames containing spaces
> and quotes?
> 

I mean... it's a less common case where filename start to have almost invalid
char but yes it's a valid point.

> > I'm open to both solution. Lets just agree on one of the 2.
> 
> I don't think any of the options will be particularly simple, but
> nul-byte delimited field support might be the most straightforward.
> 

Yes that was the initial idea but was quickly scrapped as major work is needed
in the .c tool to handle NULL separated entry.

Can you by chance point to me how the GNU tool work with --null ?


They also create a cpio_list file with entry NULL separated?


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