Re: [PATCH RESEND] romfs: reject directory entry chains that do not move forward

[Palla Raghunath]

On Tue, Sep 22, 2026 at 11:58:35AM +0200, Jan Kara wrote:
> I doubt these bugs have any practical relevance so I wouldn't CC stable.
> But I guess that's for Christian.

Fair enough. I'll drop the stable tag if there is a v2.

> The patch looks good, I'm just not sure we are guaranteed ROMFS directories
> are indeed following monotonically increasing disk offset (although that's
> the most logical thing to do) - added Dave to CC for that.

Thanks for the review, Jan.

Documentation/filesystems/romfs.rst doesn't state it, but genromfs
always lays directories out that way. processdir() hands each entry the
current offset, which only ever grows, and it places a subdirectory's
contents straight after the subdirectory's own header, before the next
sibling. Entries are added to the directory list in that same order,
and dumpnode() writes each next pointer from that list, so within one
directory every next pointer points forward. I don't know of any other
tool that builds romfs images.

If you'd rather not rely on that, I can bound the walk by the number of
16-byte header slots in the image instead. That stops a cycle without
assuming any particular order. Happy to send a v2 either way.

Thanks,
Palla