linux-kernel - Re: [PATCH] mwifiex: fix possible NULL dereference

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Date:	Mon, 11 Apr 2016 11:38:34 -0700
From:	Christian Daudt <csd@...adcom.com>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	Amitkumar Karwar <akarwar@...vell.com>,
	Nishant Sarmukadam <nishants@...vell.com>,
	Kalle Valo <kvalo@...eaurora.org>,
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org,
	Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
Subject: Re: [PATCH] mwifiex: fix possible NULL dereference

On Mon, Apr 11, 2016 at 8:27 AM, Sudip Mukherjee
<sudipm.mukherjee@...il.com> wrote:
>
> From: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
>
> We have a check for card just after dereferencing it. So if it is NULL
> we have already dereferenced it before its check. Lets dereference it
> after checking card for NULL.
>
> Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
> ---
>  drivers/net/wireless/marvell/mwifiex/pcie.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/marvell/mwifiex/pcie.c b/drivers/net/wireless/marvell/mwifiex/pcie.c
> index edf8b07..84562d0 100644
> --- a/drivers/net/wireless/marvell/mwifiex/pcie.c
> +++ b/drivers/net/wireless/marvell/mwifiex/pcie.c
> @@ -2884,10 +2884,11 @@ static void mwifiex_unregister_dev(struct mwifiex_adapter *adapter)
>  {
>         struct pcie_service_card *card = adapter->card;
>         const struct mwifiex_pcie_card_reg *reg;
> -       struct pci_dev *pdev = card->dev;
> +       struct pci_dev *pdev;


you might want to move the variable declaration into the if block
below to avoid it being left undefined

>         int i;
>
>         if (card) {
> +               pdev = card->dev;


to here
  +                struct pci_dev pdev = card->dev;

>
>                 if (card->msix_enable) {
>                         for (i = 0; i < MWIFIEX_NUM_MSIX_VECTORS; i++)
>                                 synchronize_irq(card->msix_entries[i].vector);
>

cheers,
  csd