linux-kernel - Re: general protection fault vs Oops

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Message-ID: <CAPY=qRQez4JRLGcwBq_3_AGmtH36FRrKjhCWvkhrnQxvBJEnOw@mail.gmail.com>
Date:   Mon, 18 May 2020 11:15:34 +0530
From:   Subhashini Rao Beerisetty <subhashbeerisetty@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Valdis Klētnieks <valdis.kletnieks@...edu>,
        kernelnewbies <kernelnewbies@...nelnewbies.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: general protection fault vs Oops

On Mon, May 18, 2020 at 2:16 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Sat, May 16, 2020 at 9:16 AM Subhashini Rao Beerisetty
> <subhashbeerisetty@...il.com> wrote:
> > Yes, those are out-of-tree modules. Basically, my question is, in
> > general what is the difference between 'general protection fault' and
> > 'Oops' failure in kernel mode.
>
> For your case, they are likely just different consequences of a same
> memory error. Let's assume it is a use-after-free, the behavior is UAF
> is undefined: If that memory freed by kernel is also unmapped from
> kernel address space, you would get a page fault when using it
> afterward, that is an Oops. Or if that memory freed by kernel gets
> reallocated and remapped as read-only, you would get a general
> protection error when you writing to it afterward.
Cool, thanks for the clarification.