Re: [PATCH] nbd: fix crash when the blksize is zero

[Xiubo Li]

On 2019/5/30 2:55, Mike Christie wrote:
> On 05/27/2019 12:44 AM, xiubli@xxxxxxxxxx wrote:
> > From: Xiubo Li <xiubli@xxxxxxxxxx>
> >
> > This will allow the blksize to be set zero and then use 1024 as
> > default.
> >
> > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
> > ---
> >   drivers/block/nbd.c | 21 ++++++++++++++++++---
> >   1 file changed, 18 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> > index 053958a..4c1de1c 100644
> > --- a/drivers/block/nbd.c
> > +++ b/drivers/block/nbd.c
> > @@ -135,6 +135,8 @@ struct nbd_cmd {
> >   
> >   #define NBD_MAGIC 0x68797548
> >   
> > +#define NBD_DEF_BLKSIZE 1024
> > +
> >   static unsigned int nbds_max = 16;
> >   static int max_part = 16;
> >   static struct workqueue_struct *recv_workqueue;
> > @@ -1237,6 +1239,14 @@ static void nbd_clear_sock_ioctl(struct nbd_device *nbd,
> >   		nbd_config_put(nbd);
> >   }
> >   
> > +static bool nbd_is_valid_blksize(unsigned long blksize)
> > +{
> > +	if (!blksize || !is_power_of_2(blksize) || blksize < 512 ||
> > +		blksize > PAGE_SIZE)
> > +		return false;
> > +	return true;
> > +}
> > +
> >   /* Must be called with config_lock held */
> >   static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
> >   		       unsigned int cmd, unsigned long arg)
> > @@ -1252,8 +1262,9 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
> >   	case NBD_SET_SOCK:
> >   		return nbd_add_socket(nbd, arg, false);
> >   	case NBD_SET_BLKSIZE:
> > -		if (!arg || !is_power_of_2(arg) || arg < 512 ||
> > -		    arg > PAGE_SIZE)
> > +		if (!arg)
> > +			arg = NBD_DEF_BLKSIZE;
> > +		if (!nbd_is_valid_blksize(arg))
> >   			return -EINVAL;
> >   		nbd_size_set(nbd, arg,
> >   			     div_s64(config->bytesize, arg));
> > @@ -1333,7 +1344,7 @@ static struct nbd_config *nbd_alloc_config(void)
> >   	atomic_set(&config->recv_threads, 0);
> >   	init_waitqueue_head(&config->recv_wq);
> >   	init_waitqueue_head(&config->conn_wait);
> > -	config->blksize = 1024;
> > +	config->blksize = NBD_DEF_BLKSIZE;
> >   	atomic_set(&config->live_connections, 0);
> >   	try_module_get(THIS_MODULE);
> >   	return config;
> > @@ -1769,6 +1780,10 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
> >   	if (info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]) {
> >   		u64 bsize =
> >   			nla_get_u64(info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]);
> > +		if (!bsize)
> > +			bsize = NBD_DEF_BLKSIZE;
> > +		if (!nbd_is_valid_blksize(bsize))
> > +			return -EINVAL;
> You can't only return here. You need to also drop the mutex, do
> nbd_put, and drop config_refs reference.
>
> Maybe you want to move this check to the beginning of the function with
> the NBD_ATTR_SIZE_BYTES sanity check since the error handling is easier
> there.

Yeah, right.

I saw your resend patch of this and that looks good to me.

Thanks
BRs
Xiubo


> >   		nbd_size_set(nbd, bsize, div64_u64(config->bytesize, bsize));
> >   	}
> >   	if (info->attrs[NBD_ATTR_TIMEOUT]) {