linux-kernel - Re: [PATCH] usb: storage: add error handling for kcalloc

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Date:   Tue, 12 Jun 2018 10:31:20 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Zhouyang Jia <jiazhouyang09@...il.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>,
        <usb-storage@...ts.one-eyed-alien.net>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: storage: add error handling for kcalloc

On Mon, 11 Jun 2018, Zhouyang Jia wrote:

> When kcalloc fails, the lack of error-handling code may
> cause unexpected results.
> 
> This patch adds error-handling code after calling kcalloc.
> 
> Signed-off-by: Zhouyang Jia <jiazhouyang09@...il.com>
> ---
>  drivers/usb/storage/alauda.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/usb/storage/alauda.c b/drivers/usb/storage/alauda.c
> index 900591d..c56355c 100644
> --- a/drivers/usb/storage/alauda.c
> +++ b/drivers/usb/storage/alauda.c
> @@ -437,6 +437,11 @@ static int alauda_init_media(struct us_data *us)
>  		+ MEDIA_INFO(us).blockshift + MEDIA_INFO(us).pageshift);
>  	MEDIA_INFO(us).pba_to_lba = kcalloc(num_zones, sizeof(u16*), GFP_NOIO);
>  	MEDIA_INFO(us).lba_to_pba = kcalloc(num_zones, sizeof(u16*), GFP_NOIO);
> +	if ((MEDIA_INFO(us).pba_to_lba == NULL)
> +		|| (MEDIA_INFO(us).lba_to_pba == NULL)) {
> +		pr_warn("alauda_init_media: memory allocation failed\n");
> +		return USB_STOR_TRANSPORT_ERROR;
> +	}

pr_info() isn't a good routine to use here, because it doesn't print 
the device or driver name.

In any case, a log message isn't necessary.  kcalloc() will already 
put a message in the log if either of the allocations fails.

Alan Stern

>  
>  	if (alauda_reset_media(us) != USB_STOR_XFER_GOOD)
>  		return USB_STOR_TRANSPORT_ERROR;
>