Re: bin/56300: gpt useless on gpt labels extending beyond disk size (also affects sysinst)

[jnemeth%CornerstoneService.ca@localhost (John Nemeth)]

On Aug 6, 14:20, David Brownlee wrote:
} The following reply was made to PR bin/56300; it has been noted by GNATS.
} 
} From: David Brownlee <abs%absd.org@localhost>
} To: gnats-bugs%netbsd.org@localhost
} Subject: Re: bin/56300: gpt useless on gpt labels extending beyond disk size
}  (also affects sysinst)
} Date: Sun, 6 Aug 2023 15:15:05 +0100
} 
}  Just hit this when trying to adjust some gpt-in-ccd settings
}  
}  Also - easy case to reproduce (without the 'gpt add' step it does not
}  trigger)
}  
}  dd if=/dev/zero bs=1m count=10 > test.img
}  gpt create test.img
}  gpt add -t ffs test.img
}  dd if=test.img of=smaller.img bs=1m count=9
}  gpt destroy smaller.img
}  
}  One thought, there could be some kind of force option to bypass the size
}  check - possibly by truncating or ignoring oversized entries, which could
}  be useful for recovering damaged disk images

     The problem is that gpt(8) looks like a first year comp-sci
assignment in linked list manipulation.  The program is all about
manipulating the list, where the nodes just happen to represent
disk objects.  It's not very good at handling situations where the
linked list could get "corrupted".

     I've been thinking about ideas for a new data structure.  My
first idea involved using bitmasks, but I realized that with the
size of modern disks that was a no go.  I'm open to ideas.

}-- End of excerpt from David Brownlee