linux-kernel - Re: [PATCH v3] ALSA: ymfpci: Handle return NULL error from ioremap

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Date:   Wed, 25 Jan 2017 22:31:07 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     "Arvind Yadav" <arvind.yadav.cs@...il.com>
Cc:     <perex@...ex.cz>, <alsa-devel@...a-project.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] ALSA: ymfpci:  Handle return NULL error from ioremap_nocache

On Tue, 24 Jan 2017 06:31:26 +0100,
Arvind Yadav wrote:
> 
> Here, If ioremap_nocache will fail. It will return NULL.
> Kernel can run into a NULL-pointer dereference.
> This error check will avoid NULL pointer dereference.
> 
> Signed-off-by: Arvind Yadav <arvind.yadav.cs@...il.com>
> ---
>  sound/pci/ymfpci/ymfpci_main.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/sound/pci/ymfpci/ymfpci_main.c b/sound/pci/ymfpci/ymfpci_main.c
> index ffee284..8be1f07 100644
> --- a/sound/pci/ymfpci/ymfpci_main.c
> +++ b/sound/pci/ymfpci/ymfpci_main.c
> @@ -2392,6 +2392,10 @@ int snd_ymfpci_create(struct snd_card *card,
>  	chip->rev = pci->revision;
>  	chip->reg_area_phys = pci_resource_start(pci, 0);
>  	chip->reg_area_virt = ioremap_nocache(chip->reg_area_phys, 0x8000);
> +	if (!chip->reg_area_virt) {
> +		snd_ymfpci_free(chip);

The function calls iounmap() unconditionally, so it's not appropriate
to call as is.  You need to fix snd_ymfpci_free() as well to check
NULL before iounmap().  Or, call here kfree() and pci_disable_device()
explicitly instead of a full destructor.


thanks,

Takashi