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Message-ID: <a0afa88b-f84c-4b45-a265-2e6bcbb84b35@rowland.harvard.edu>
Date: Thu, 23 May 2024 09:58:21 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Shichao Lai <shichaorai@...il.com>
Cc: gregkh@...uxfoundation.org, oneukum@...e.com, linux-usb@...r.kernel.org,
usb-storage@...ts.one-eyed-alien.net, linux-kernel@...r.kernel.org,
xingwei lee <xrivendell7@...il.com>, yue sun <samsun1006219@...il.com>
Subject: Re: [PATCHv2] Check whether divisor is non-zero before division
On Thu, May 23, 2024 at 05:26:08PM +0800, Shichao Lai wrote:
> Since uzonesize may be zero, so judgements for non-zero are nessesary in both place.
> Previous check is moved out of loop, and one more check is added in alauda_write_lba.
>
> Reported-by: xingwei lee <xrivendell7@...il.com>
> Reported-by: yue sun <samsun1006219@...il.com>
> Signed-off-by: Shichao Lai <shichaorai@...il.com>
> ---
> drivers/usb/storage/alauda.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/usb/storage/alauda.c b/drivers/usb/storage/alauda.c
> index 115f05a6201a..a6e60ef5cb0d 100644
> --- a/drivers/usb/storage/alauda.c
> +++ b/drivers/usb/storage/alauda.c
> @@ -818,6 +818,8 @@ static int alauda_write_lba(struct us_data *us, u16 lba,
> unsigned int blocksize = MEDIA_INFO(us).blocksize;
> unsigned int lba_offset = lba % uzonesize;
> unsigned int new_pba_offset;
> + if (!uzonesize)
> + return USB_STOR_TRANSPORT_ERROR;
> unsigned int zone = lba / uzonesize;
>
> alauda_ensure_map_for_zone(us, zone);
> @@ -923,6 +925,8 @@ static int alauda_read_data(struct us_data *us, unsigned long address,
> unsigned int uzonesize = MEDIA_INFO(us).uzonesize;
> struct scatterlist *sg;
> int result;
> + if (!uzonesize)
> + return USB_STOR_TRANSPORT_ERROR;
>
> /*
> * Since we only read in one block at a time, we have to create
This is definitely NOT the right way to fix the bug!
uzonesize is set once, when the device is probed, in
alauda_init_media(). That is where the check belongs; if uzonesize is 0
then the function should print a warning and return
USB_STOR_TRANSPORT_ERROR, because the device is unusable.
It's probably a good idea to check pagesize, blocksize, and zonesize at
the same time, even though none of them are used for any divisions.
Alan Stern
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