linux-kernel - Re: [PATCH] USB: storage: Fix potential NULL pointer derefernce

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Message-ID: <Pine.LNX.4.44L0.1903131355570.1405-100000@iolanthe.rowland.org>
Date:   Wed, 13 Mar 2019 14:01:08 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Aditya Pakki <pakki001@....edu>
cc:     kjlu@....edu, 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: Fix potential NULL pointer derefernce

On Wed, 13 Mar 2019, Aditya Pakki wrote:

> Allocating memory via kcalloc for pba_to_lba and lba_to_pba can
> fail. The fix avoids a potential NULL pointer dereference.
> 
> Signed-off-by: Aditya Pakki <pakki001@....edu>
> ---
>  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 6b8edf6178df..41d979e70784 100644
> --- a/drivers/usb/storage/alauda.c
> +++ b/drivers/usb/storage/alauda.c
> @@ -438,6 +438,11 @@ static int alauda_init_media(struct us_data *us)
>  	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 || !MEDIA_INFO(us).lba_to_pba) {
> +		pr_warn("%s: Failed to allocate memory\n", __func__);
> +		return USB_STOR_TRANSPORT_ERROR;
> +	}
> +
>  	if (alauda_reset_media(us) != USB_STOR_XFER_GOOD)
>  		return USB_STOR_TRANSPORT_ERROR;

In fact this won't accomplish anything, because the return value from 
alauda_init_media() isn't used.  The driver appears to need more than 
a single change.

Alan Stern