linux-kernel - Re: [Linux Kernel Bug][mm/gup] 3 Warning Crashes: kmalloc bug in gup_test_ioctl, is_valid_gup_args, pin_user_pages

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Date: Fri, 26 Jan 2024 18:34:54 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Chenyuan Yang <chenyuan0y@...il.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, syzkaller@...glegroups.com,
	Zijie Zhao <zzjas98@...il.com>, John Hubbard <jhubbard@...dia.com>
Subject: Re: [Linux Kernel Bug][mm/gup] 3 Warning Crashes: kmalloc bug in
 gup_test_ioctl, is_valid_gup_args, pin_user_pages_fast

On Fri, Jan 26, 2024 at 11:31:26AM -0600, Chenyuan Yang wrote:
> In this context, I would like to seek your valued opinion. Do you
> believe it would be more prudent to avoid fuzz testing the
> `gup_test_ioctl`, or are the warnings in `gup_test_ioctl` an
> anticipated outcome?

It seems like a waste of time.  Debian certainly disables it, so
unless you can find a distro who enables it, I wouldn't bother.

> It seems that `gup_test_ioctl` can indeed be exposed in the kernel by
> accessing /sys/kernel/debug/gup_test.

If someone wants to fix these things, they can, but it just doesn't
seem worth doing.  Part of the art of fuzz testing is finding things
that are worth testing.