From: Linus Torvalds <email@example.com>
To: Andy Lutomirski <firstname.lastname@example.org>
Cc: Peter Zijlstra <email@example.com>,
Andrew Morton <firstname.lastname@example.org>,
Linux Kernel Mailing List <email@example.com>,
Jens Axboe <firstname.lastname@example.org>, Kees Cook <email@example.com>,
Jann Horn <firstname.lastname@example.org>, Will Deacon <email@example.com>
Subject: Re: [PATCH] mm/tlb: Fix use_mm() vs TLB invalidate
Date: Fri, 21 Feb 2020 11:26:29 -0800 [thread overview]
Message-ID: <CAHk-=whDHsbK3HTOpTF=ue_o04onRwTEaK_ZoJp_fjbqq4+=Jw@mail.gmail.com> (raw)
On Fri, Feb 21, 2020 at 11:22 AM Andy Lutomirski <firstname.lastname@example.org> wrote:
> In this particular case, if we actually flub this, we are very likely to cause data corruption — we’re about to do user access with the wrong mm.
IF this ever triggers, it has presumably been around for decades.
Adding a WARN_ON_ONCE() means that somebody will now notice. Good.
Adding a BUG_ON() will now possibly mean that the machine is dead, and
is not sending the bug-report to anybody.
It's not going to hit, of course. But if you are 100% sure of that,
then it shouldn't exist at all.
And if you're not 100% sure of it, then it's going to be in some very
unusual circumstances (possibly some odd driver subsystem that does
something completely wrong - wouldn't be the first time), and the last
thing you want to do is lose the information about it.
So BUG_ON() is basically ALWAYS 100% the wrong thing to do. The
argument that "there could be memory corruption" is complete and utter
garbage. See above why.
Stop it. Seriously.
next prev parent reply other threads:[~2020-02-21 19:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-21 11:11 [PATCH] mm/tlb: Fix use_mm() vs TLB invalidate Peter Zijlstra
2020-02-21 19:19 ` Linus Torvalds
2020-02-21 19:22 ` Andy Lutomirski
2020-02-21 19:26 ` Linus Torvalds [this message]
2020-02-21 23:10 ` Kees Cook
2020-02-21 23:57 ` Linus Torvalds
2020-02-22 0:29 ` Kees Cook
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