Re: fsck segfaults on rpi3 running 13-stable (and on 14-CURRENT analyzing the same file system that resulted from the 13-STABLE crash)

On Tue, Feb 14, 2023 at 10:38:27AM -0800, John-Mark Gurney wrote:
> bob prohaska wrote this message on Tue, Feb 14, 2023 at 08:14 -0800:
> > 
> > Is this a demonstration that the fsck segfault can be reproduced 
> > independtly of my particular corrupt filesystem? AFL is new to me. 
> 
> Yes, it is.  It turns out that the FS to produce this failure is a LOT
> smaller than I expected when compresed, I have included it later in the
> email.  The constant above was taken directly from the failing FS.
> 
> AFL is a very useful tool, and found this crash and apparently 50+
> other crashes in only 5-10 minutes of running... I'll be investigating
> a few of the other crashes as well, as fsck does ocassionally deal w/
> untrusted fs's.
> 

Would trying to run fsck on the corrupt filesystem from an 8GB Pi4
(also running -current) make any difference? I.e., might more physical
RAM cover up the bug and allow fsck to complete successfully? 

Is there a plain-English description of how AFL works? I gather it
manipulates input read by a program to discover improperly handled
cases, but even that is far from certain. There's no hope of me doing 
anything useful with AFL. I'm merely curious.  

Thanks very much for writing!

bob  prohaska