linux-kernel - Re: [syzbot] [mm?] WARNING in __gup_longterm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAHk-=wjvVRv7yfsAYyRigSWxKyeMb42yzB3hj2U9J1u59MyvUg@mail.gmail.com>
Date:   Tue, 4 Jul 2023 10:13:17 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        syzbot <syzbot+6cf44e127903fdf9d929@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] WARNING in __gup_longterm_locked

On Tue, 4 Jul 2023 at 10:01, Eric Biggers <ebiggers@...nel.org> wrote:
>
> syzkaller just makes system calls.
>
> Unless you want to do the crazy thing of checking if current->comm begins with
> "syz", I don't think there is a way to distinguish.

Yeah, that's what I thought.

> In the past there's been some discussion of adding a kconfig option like
> CONFIG_FUZZ_TESTING that would be expected to be enabled in order to run a
> kernel fuzzer, and changing behavior in certain cases based on that.  Changing
> behavior in production vs. test is problematic, though...

Agreed. The whole point of a fuzzer is to check the real thing. This
test for GUP expansion really is a pretty specialized thing.

Maybe the WARN_ON_ONCE() could have been just a "pr_warn_once()", but
at the same time, *if* that condition ever happens in some real
situation, I'd really want to know just exactly *what* the app in
question is doing.

                 Linus