Re: [PATCH 2/2] initramfs_test: test header fields with 0x hex prefix

[David Disseldorp <ddiss@suse.de>]

On Wed, 21 Jan 2026 00:18:31 +0200, Andy Shevchenko wrote:

> On Wed, Jan 21, 2026 at 07:32:33AM +1100, David Disseldorp wrote:
> > cpio header fields are 8-byte hex strings, but one "interesting"
> > side-effect of our historic simple_str[n]toul() use means that a "0x"
> > prefixed header field will be successfully processed when coupled
> > alongside a 6-byte hex remainder string.  
> 
> Should mention that this is against specifications.
> 
> > Test for this corner case by injecting "0x" prefixes into the uid, gid
> > and namesize cpio header fields. Confirm that init_stat() returns
> > matching uid and gid values.  
> 
> This is should be considered as an invalid case and I don't believe
> we ever had that bad header somewhere. The specification is clear
> that the number has to be filled with '0' to the most significant
> byte until all 8 positions are filled.
> 
> If any test case like this appears it should not be fatal.

Yes, the test case can easily be changed to expect an unpack_to_rootfs()
error (or dropped completely). The purpose is just to ensure that the
user visible change is a concious decision rather than an undocumented
side effect.

Cheers, David