linux-kernel - Re: [PATCH v2] vt: Fix a missing-check bug in drivers/tty/vt/vt.c

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

Message-ID: <nycvar.YSQ.7.76.1905202323290.1558@knanqh.ubzr>
Date:   Mon, 20 May 2019 23:26:20 -0400 (EDT)
From:   Nicolas Pitre <nico@...xnic.net>
To:     Gen Zhang <blackgod016574@...il.com>
cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vt: Fix a missing-check bug in drivers/tty/vt/vt.c

On Tue, 21 May 2019, Gen Zhang wrote:

> On Mon, May 20, 2019 at 10:55:40PM -0400, Nicolas Pitre wrote:
> > On Tue, 21 May 2019, Gen Zhang wrote:
> > 
> > > In function con_init(), the pointer variable vc_cons[currcons].d, vc and
> > > vc->vc_screenbuf is allocated a memory space via kzalloc(). And they are
> > > used in the following codes.
> > > However, when there is a memory allocation error, kzalloc() can fail.
> > > Thus null pointer (vc_cons[currcons].d, vc and vc->vc_screenbuf)
> > > dereference may happen. And it will cause the kernel to crash. Therefore,
> > > we should check return value and handle the error.
> > > Further,the loop condition MIN_NR_CONSOLES is defined as 1 in
> > > include/uapi/linux/vt.h. So there is no need to unwind the loop.
> > 
> > But what if someone changes that define? It won't be obvious that some 
> > code did rely on it to be defined to 1.
> I re-examine the source code. MIN_NR_CONSOLES is only defined once and
> no other changes to it.

Yes, that is true today.  But if someone changes that in the future, how 
will that person know that you relied on it to be 1 for not needing to 
unwind the loop?


Nicolas