linux-kernel - Re: [PATCH] sunvdc: Remove VLA usage

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Message-ID: <CAGXu5jKV3eLJJsemxNEjZuANRd8-TnRkMSmiztVyY5mgC2ySHw@mail.gmail.com>
Date:   Sun, 7 Oct 2018 23:16:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Jens Axboe <axboe@...nel.dk>,
        linux-block <linux-block@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sunvdc: Remove VLA usage

On Mon, Sep 24, 2018 at 8:19 PM, Kees Cook <keescook@...omium.org> wrote:
> On Wed, Sep 5, 2018 at 5:09 PM, Kees Cook <keescook@...omium.org> wrote:
>> In the quest to remove all stack VLA usage from the kernel[1], this
>> moves the math for cookie calculation into macros and allocates a fixed
>> size array for the maximum number of cookies and adds a runtime sanity check.
>> (Note that the size was always fixed, but just hidden from the compiler.)
>>
>> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>
> Friendly ping. Jens, can you take this?

Dave, should this go via you instead? I'll take it via my tree if no
one else wants it...

Thanks,

-Kees

>
> Thanks!
>
> -Kees
>
>> ---
>>  drivers/block/sunvdc.c | 14 ++++++++++----
>>  1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/block/sunvdc.c b/drivers/block/sunvdc.c
>> index 5ca56bfae63c..f68e9baffad7 100644
>> --- a/drivers/block/sunvdc.c
>> +++ b/drivers/block/sunvdc.c
>> @@ -36,6 +36,10 @@ MODULE_VERSION(DRV_MODULE_VERSION);
>>  #define VDC_TX_RING_SIZE       512
>>  #define VDC_DEFAULT_BLK_SIZE   512
>>
>> +#define MAX_XFER_BLKS          (128 * 1024)
>> +#define MAX_XFER_SIZE          (MAX_XFER_BLKS / VDC_DEFAULT_BLK_SIZE)
>> +#define MAX_RING_COOKIES       ((MAX_XFER_BLKS / PAGE_SIZE) + 2)
>> +
>>  #define WAITING_FOR_LINK_UP    0x01
>>  #define WAITING_FOR_TX_SPACE   0x02
>>  #define WAITING_FOR_GEN_CMD    0x04
>> @@ -450,7 +454,7 @@ static int __send_request(struct request *req)
>>  {
>>         struct vdc_port *port = req->rq_disk->private_data;
>>         struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
>> -       struct scatterlist sg[port->ring_cookies];
>> +       struct scatterlist sg[MAX_RING_COOKIES];
>>         struct vdc_req_entry *rqe;
>>         struct vio_disk_desc *desc;
>>         unsigned int map_perm;
>> @@ -458,6 +462,9 @@ static int __send_request(struct request *req)
>>         u64 len;
>>         u8 op;
>>
>> +       if (WARN_ON(port->ring_cookies > MAX_RING_COOKIES))
>> +               return -EINVAL;
>> +
>>         map_perm = LDC_MAP_SHADOW | LDC_MAP_DIRECT | LDC_MAP_IO;
>>
>>         if (rq_data_dir(req) == READ) {
>> @@ -984,9 +991,8 @@ static int vdc_port_probe(struct vio_dev *vdev, const struct vio_device_id *id)
>>                 goto err_out_free_port;
>>
>>         port->vdisk_block_size = VDC_DEFAULT_BLK_SIZE;
>> -       port->max_xfer_size = ((128 * 1024) / port->vdisk_block_size);
>> -       port->ring_cookies = ((port->max_xfer_size *
>> -                              port->vdisk_block_size) / PAGE_SIZE) + 2;
>> +       port->max_xfer_size = MAX_XFER_SIZE;
>> +       port->ring_cookies = MAX_RING_COOKIES;
>>
>>         err = vio_ldc_alloc(&port->vio, &vdc_ldc_cfg, port);
>>         if (err)
>> --
>> 2.17.1
>>
>>
>> --
>> Kees Cook
>> Pixel Security
>
>
>
> --
> Kees Cook
> Pixel Security



-- 
Kees Cook
Pixel Security