linux-kernel - Re: [PATCH 2/3] staging: ion: Fix possible null pointer dereference

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Message-ID: <CAMbhsRTczY7zwCAYtrXm9EsfT+BLnJy_rnbf35cFOQ_303ODCA@mail.gmail.com>
Date:	Mon, 16 Dec 2013 23:26:02 -0800
From:	Colin Cross <ccross@...roid.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	kbuild test robot <fengguang.wu@...el.com>
Subject: Re: [PATCH 2/3] staging: ion: Fix possible null pointer dereference

On Mon, Dec 16, 2013 at 9:07 PM, John Stultz <john.stultz@...aro.org> wrote:
> The kbuild test robot reported:
>
> drivers/staging/android/ion/ion_system_heap.c:122 alloc_largest_available() error: potential null dereference 'info'.  (kmalloc returns null)
>
> Where the pointer returned from kmalloc goes unchecked for failure.
>
> This patch checks the return for NULL, and reworks the logic, as
> suggested by Colin, so we allocate the page_info structure first.
>
> Cc: Colin Cross <ccross@...roid.com>
> Cc: Greg KH <gregkh@...uxfoundation.org>
> Cc: Android Kernel Team <kernel-team@...roid.com>
> Cc: kbuild test robot <fengguang.wu@...el.com>
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
>  drivers/staging/android/ion/ion_system_heap.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> index 144b2272..7f07291 100644
> --- a/drivers/staging/android/ion/ion_system_heap.c
> +++ b/drivers/staging/android/ion/ion_system_heap.c
> @@ -108,6 +108,10 @@ static struct page_info *alloc_largest_available(struct ion_system_heap *heap,
>         struct page_info *info;
>         int i;
>
> +       info = kmalloc(sizeof(struct page_info), GFP_KERNEL);
> +       if (!info)
> +               return NULL;
> +
>         for (i = 0; i < num_orders; i++) {
>                 if (size < order_to_size(orders[i]))
>                         continue;
> @@ -118,11 +122,12 @@ static struct page_info *alloc_largest_available(struct ion_system_heap *heap,
>                 if (!page)
>                         continue;
>
> -               info = kmalloc(sizeof(struct page_info), GFP_KERNEL);
>                 info->page = page;
>                 info->order = orders[i];
>                 return info;
>         }
> +       kfree(info);
> +
>         return NULL;
>  }
>

Acked-by: Colin Cross <ccross@...roid.com>
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