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

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Jan 22, 2026 at 03:17:02AM +1100, David Disseldorp wrote:
> On Wed, 21 Jan 2026 15:15:54 +0200, Andy Shevchenko wrote:
> > On Wed, Jan 21, 2026 at 08:42:05PM +1100, David Disseldorp wrote:
> > > 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.
> 
> I've added this and will send as v2.

Thanks!

> > > > > 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.  
> > 
> > Can you say this clearly in the commit message? With that done I will have
> > no objections as it seems we all agree with the possible breakage of this
> > "feature" (implementation detail).
> 
> Sure, I think it'd make sense to put the v2 test patches as 1/2 in your
> series such that your subsequent hex2bin() patch modifies the test to
> expect error. E.g.

Yes! Thanks for providing a PoC. Maybe you can do it as a formal patch that
I can simply take into my next version?

-- 
With Best Regards,
Andy Shevchenko