linux-kernel - Re: [PATCH v3] lkdtm/bugs: Check for the NULL pointer after calling kmalloc

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Message-ID: <YekBrYDA+/Vxxwwr@kroah.com>
Date:   Thu, 20 Jan 2022 07:31:09 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     keescook@...omium.org, dan.carpenter@...cle.com, arnd@...db.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] lkdtm/bugs: Check for the NULL pointer after calling
 kmalloc

On Thu, Jan 20, 2022 at 09:25:51AM +0800, Jiasheng Jiang wrote:
> As the possible failure of the kmalloc(), the not_checked and checked
> could be NULL pointer.
> Therefore, it should be better to check it in order to avoid the
> dereference of the NULL pointer.
> Also, we need to explicitly yell about the memory failure and then
> kfree the 'not_checked' and 'checked' to avoid the memory leak if fails.
> And since it is just a test, it may directly return without error
> number.
> 
> Fixes: ae2e1aad3e48 ("drivers/misc/lkdtm/bugs.c: add arithmetic overflow and array bounds checks")
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
> Changelog
> 
> v1 -> v2
> 
> * Change 1. Add the kfree if fails.
> 
> v2 -> v3
> 
> * Change 1. Add pr_err if fails.
> ---
>  drivers/misc/lkdtm/bugs.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
> index f4cb94a9aa9c..c64ab6f387eb 100644
> --- a/drivers/misc/lkdtm/bugs.c
> +++ b/drivers/misc/lkdtm/bugs.c
> @@ -325,6 +325,12 @@ void lkdtm_ARRAY_BOUNDS(void)
>  
>  	not_checked = kmalloc(sizeof(*not_checked) * 2, GFP_KERNEL);
>  	checked = kmalloc(sizeof(*checked) * 2, GFP_KERNEL);
> +	if (!not_checked || !checked) {
> +		pr_err("FAIL: could not allocate required buffers!\n");

As was pointed out, this is now a checkpatch failure :(