Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <CAPY=qRQ6gzN1BWh=ianVDBQ1C9kibWHwxs5Z0+QSwGxKymLDTQ@mail.gmail.com>
 <374485.1589637193@turing-police> <af03bee5-27b2-4e92-359a-b1cc8f500d6d@infradead.org>
 <CAPY=qRRJ6aZbbRnWfvjqojs08Z7H-+-6nzLAcpzjDcQOJ40fOQ@mail.gmail.com>
In-Reply-To: <CAPY=qRRJ6aZbbRnWfvjqojs08Z7H-+-6nzLAcpzjDcQOJ40fOQ@mail.gmail.com>
From:   Cong Wang <xiyou.wangcong@gmail.com>
Date:   Sun, 17 May 2020 13:46:39 -0700
Message-ID: <CAM_iQpXzeMjAUW0LNMpGf+bqykU8fjOJmy=CDdNEPQNpSB4raA@mail.gmail.com>
Subject: Re: general protection fault vs Oops
To:     Subhashini Rao Beerisetty <subhashbeerisetty@gmail.com>
Cc:     Randy Dunlap <rdunlap@infradead.org>,
        =?UTF-8?Q?Valdis_Kl=C4=93tnieks?= <valdis.kletnieks@vt.edu>,
        kernelnewbies <kernelnewbies@kernelnewbies.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sat, May 16, 2020 at 9:16 AM Subhashini Rao Beerisetty
<subhashbeerisetty@gmail.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.