[PATCH v3] ALSA: ymfpci: Handle return NULL error from ioremap_nocache

[PATCH v3] ALSA: ymfpci: Handle return NULL error from ioremap_nocache

[Arvind Yadav]

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@gmail.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);
+		return -ENOMEM;
+	}
 	pci_set_master(pci);
 	chip->src441_used = -1;
 
-- 
1.9.1

Re: [PATCH v3] ALSA: ymfpci: Handle return NULL error from ioremap_nocache

[Takashi Iwai]

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@gmail.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