linux-kernel - Re: [PATCH v2 7/9] vdpa: solidrun: Fix potential UB bug with devres

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Message-ID: <cf9591d720c9b25dafd46b627ff8b6ed9f417745.camel@redhat.com>
Date: Wed, 21 Aug 2024 14:25:57 +0200
From: Philipp Stanner <pstanner@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: Jonathan Corbet <corbet@....net>, Jens Axboe <axboe@...nel.dk>, Wu Hao
 <hao.wu@...el.com>, Tom Rix <trix@...hat.com>, Moritz Fischer
 <mdf@...nel.org>,  Xu Yilun <yilun.xu@...el.com>, Andy Shevchenko
 <andy@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, Bartosz
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 Kleine-König <u.kleine-koenig@...gutronix.de>, Damien Le
 Moal <dlemoal@...nel.org>,  Hannes Reinecke <hare@...e.de>, Keith Busch
 <kbusch@...nel.org>, linux-doc@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-block@...r.kernel.org, 
 linux-fpga@...r.kernel.org, linux-gpio@...r.kernel.org,
 netdev@...r.kernel.org,  linux-stm32@...md-mailman.stormreply.com,
 linux-arm-kernel@...ts.infradead.org,  linux-pci@...r.kernel.org,
 virtualization@...ts.linux.dev,  stable@...r.kernel.org, Christophe JAILLET
 <christophe.jaillet@...adoo.fr>
Subject: Re: [PATCH v2 7/9] vdpa: solidrun: Fix potential UB bug with devres

On Wed, 2024-08-21 at 08:12 -0400, Michael S. Tsirkin wrote:
> On Wed, Aug 21, 2024 at 09:18:40AM +0200, Philipp Stanner wrote:
> > In psnet_open_pf_bar() a string later passed to
> > pcim_iomap_regions() is
> > placed on the stack. Neither pcim_iomap_regions() nor the functions
> > it
> > calls copy that string.
> > 
> > Should the string later ever be used, this, consequently, causes
> > undefined behavior since the stack frame will by then have
> > disappeared.
> > 
> > Fix the bug by allocating the string on the heap through
> > devm_kasprintf().
> > 
> > Cc: stable@...r.kernel.org	# v6.3
> > Fixes: 51a8f9d7f587 ("virtio: vdpa: new SolidNET DPU driver.")
> > Reported-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> > Closes:
> > https://lore.kernel.org/all/74e9109a-ac59-49e2-9b1d-d825c9c9f891@wanadoo.fr/
> > Suggested-by: Andy Shevchenko <andy@...nel.org>
> > Signed-off-by: Philipp Stanner <pstanner@...hat.com>
> 
> I don't get why is this a part of a cleanup series -
> looks like an unrelated bugfix?

It was discovered in the discussion of v1 of this series.

It indeed is an unrelated bugfix and could be merged separately. But my
patch #8 depends on it.

So it would be convenient to merge it into mainline through this
series, and have stable just pick patch #7.

Or should it be done differently, in your opinion?

P.

> 
> 
> > ---
> >  drivers/vdpa/solidrun/snet_main.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/vdpa/solidrun/snet_main.c
> > b/drivers/vdpa/solidrun/snet_main.c
> > index 99428a04068d..4d42a05d70fc 100644
> > --- a/drivers/vdpa/solidrun/snet_main.c
> > +++ b/drivers/vdpa/solidrun/snet_main.c
> > @@ -555,7 +555,7 @@ static const struct vdpa_config_ops
> > snet_config_ops = {
> >  
> >  static int psnet_open_pf_bar(struct pci_dev *pdev, struct psnet
> > *psnet)
> >  {
> > -	char name[50];
> > +	char *name;
> >  	int ret, i, mask = 0;
> >  	/* We don't know which BAR will be used to communicate..
> >  	 * We will map every bar with len > 0.
> > @@ -573,7 +573,10 @@ static int psnet_open_pf_bar(struct pci_dev
> > *pdev, struct psnet *psnet)
> >  		return -ENODEV;
> >  	}
> >  
> > -	snprintf(name, sizeof(name), "psnet[%s]-bars",
> > pci_name(pdev));
> > +	name = devm_kasprintf(&pdev->dev, GFP_KERNEL, "psnet[%s]-
> > bars", pci_name(pdev));
> > +	if (!name)
> > +		return -ENOMEM;
> > +
> >  	ret = pcim_iomap_regions(pdev, mask, name);
> >  	if (ret) {
> >  		SNET_ERR(pdev, "Failed to request and map PCI
> > BARs\n");
> > -- 
> > 2.46.0
>