linux-kernel - Re: [syzbot] [xfs?] INFO: task hung in __fdget

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Message-ID: <20230904032658.GA701295@mit.edu>
Date:   Sun, 3 Sep 2023 23:26:58 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Dave Chinner <david@...morbit.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Mateusz Guzik <mjguzik@...il.com>,
        syzbot <syzbot+e245f0516ee625aaa412@...kaller.appspotmail.com>,
        brauner@...nel.org, djwong@...nel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-xfs@...r.kernel.org, llvm@...ts.linux.dev, nathan@...nel.org,
        ndesaulniers@...gle.com, syzkaller-bugs@...glegroups.com,
        trix@...hat.com
Subject: Re: [syzbot] [xfs?] INFO: task hung in __fdget_pos (4)

On Mon, Sep 04, 2023 at 11:45:03AM +1000, Dave Chinner wrote:
> Entirely possible - this is syzbot we are talking about here.
> Especially if reiser or ntfs has been tested back before the logs we
> have start, as both are known to corrupt memory and/or leak locks
> when trying to parse corrupt filesystem images that syzbot feeds
> them.  That's why we largely ignore syzbot reports that involve
> those filesystems...
> 
> Unfortunately, the logs from what was being done around when the
> tasks actually hung are long gone (seems like only the last 20-30s
> of log activity is reported) so when the hung task timer goes off
> at 143s, there is nothing left to tell us what might have caused it.
> 
> IOWs, it's entirely possible that it is a memory corruption that
> has resulted in a leaked lock somewhere...

... and this is why I ignore any syzbot report that doesn't have a C
reproducer.  Life is too short to waste time with what is very likely
syzbot noise....  And I'd much rather opt out of the gamification of
syzbot dashboards designed to use dark patterns to guilt developers to
work on "issues" that very likely have no real impact on real life
actual user impact, if it might cause developers and maintainers to
burn out and quit.

Basically, if syzbot won't prioritize things for us, it's encumbent on
us to prioritize things for our own mental health.  And so syzbot
issues without a real reproducer are very low on my priority list; I
have things I can work on that are much more likely to make real world
impact.  Even ones that have a real reproducer, there are certain
classes of bugs (e.g., "locking bugs" that require a badly corrupted
file system, or things that are just denial of service attacks if
you're too stupid to insert a USB thumb drive found in a parking lock
--- made worse by GNOME who has decided to default mount any random
USB thumb drive inserted into a system, even a server system that has
GNOME installed, thanks to some idiotic decision made by some random
Red Hat product manager), that I just ignore because I don't have
infinite amounts of time to coddle stupid Red Hat distro tricks.

						- Ted