linux-kernel - Re: [PATCH] vduse: Fix off by one in vduse_dev

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Message-ID: <81e2238e-3ed8-44dc-82fe-256155c271ba@moroto.mountain>
Date: Wed, 28 Feb 2024 20:42:52 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Cindy Lu <lulu@...hat.com>, Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Xie Yongji <xieyongji@...edance.com>,
	Maxime Coquelin <maxime.coquelin@...hat.com>,
	Christian Brauner <brauner@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] vduse: Fix off by one in vduse_dev_mmap()

On Tue, Feb 27, 2024 at 10:48:49AM -0500, Michael S. Tsirkin wrote:
> On Tue, Feb 27, 2024 at 06:21:46PM +0300, Dan Carpenter wrote:
> > The dev->vqs[] array has "dev->vq_num" elements.  It's allocated in
> > vduse_dev_init_vqs().  Thus, this > comparison needs to be >= to avoid
> > reading one element beyond the end of the array.
> > 
> > Fixes: 316ecd1346b0 ("vduse: Add file operation for mmap")
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> 
> 
> Oh wow and does this not come from userspace? If yes we
> need the speculation magic macro when using the index, do we not?
> 

Yes, it does come from userspace.

To be honest, I'm not sure about speculation.  The similar places in
this file protect against speculation so, probably?  I'll resend the
patch.

regards,
dan carpenter