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Message-ID: <MWHPR05MB33760A2F7ABC03DB367B09C2DAF00@MWHPR05MB3376.namprd05.prod.outlook.com>
Date: Mon, 23 Mar 2020 10:16:43 +0000
From: Jorgen Hansen <jhansen@...are.com>
To: 'Arnd Bergmann' <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: Xiyu Yang <xiyuyang19@...an.edu.cn>,
Alexios Zavras <alexios.zavras@...el.com>,
Allison Randal <allison@...utok.net>,
Adit Ranadive <aditr@...are.com>,
Thomas Gleixner <tglx@...utronix.de>,
Vishnu Dasa <vdasa@...are.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"yuanxzhang@...an.edu.cn" <yuanxzhang@...an.edu.cn>,
"kjlu@....edu" <kjlu@....edu>, Xin Tan <tanxin.ctf@...il.com>
Subject: RE: [PATCH v2] VMCI: Fix NULL pointer dereference on context ptr
> From: Arnd Bergmann [mailto:arnd@...db.de]
> Sent: Monday, March 23, 2020 10:17 AM
> On Mon, Mar 23, 2020 at 9:52 AM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > On Mon, Mar 23, 2020 at 04:22:33PM +0800, Xiyu Yang wrote:
> > > A NULL vmci_ctx object may pass to vmci_ctx_put() from its callers.
> >
> > Are you sure this can happen?
> >
> > > Add a NULL check to prevent NULL pointer dereference.
>
> It looks like this could happen if vmci_ctx_get() returns NULL, which is
> not checked for consistently. Maybe add better error handling to the
> callers that currently don't check for that, to catch problems such as
In the cases, where the return value isn't checked, the return value of
vmci_ctx_get() won't be NULL, as the code won't be reached unless the
context ID has an associated context structure. In the example below,
the caller has obtained the context_id from an active context. That said,
it wouldn't hurt to add either checks or at least a comment as to why
the context won't be NULL in the cases, where it isn't checked today.
>
> void vmci_ctx_rcv_notifications_release(...)
> {
> struct vmci_ctx *context = vmci_ctx_get(context_id); /* may be NULL */
> ...
> context->pending_doorbell_array = db_handle_array;
> ...
> vmci_ctx_put(context);
> }
>
> Checking only in vmci_ctx_put() is too late.
>
> Arnd
Thanks,
Jorgen
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