Re: [PATCH for-next V8 6/6] IB/ucma: HW Device hot-removal support

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Wed, Aug 19, 2015 at 04:59:11PM +0300, Yishai Hadas wrote:
> On 8/18/2015 8:50 PM, Jason Gunthorpe wrote:
> >On Thu, Aug 13, 2015 at 06:32:07PM +0300, Yishai Hadas wrote:
> >>@@ -501,10 +586,24 @@ static ssize_t ucma_destroy_id(struct ucma_file *file, const char __user *inbuf,
> >>+	if (!ctx->closing) {
> >>+		mutex_unlock(&mut);
> >>+		ucma_put_ctx(ctx);
> >>+		wait_for_completion(&ctx->comp);
> >>+		rdma_destroy_id(ctx->cm_id);
> >
> >Suggest nulling cm_id after it is destroyed in all places, this code
> >is very complicated, I'd rather see a nice clean risk of
> >null-pointer-deref than an undetected use-after free if it gets messed
> >up.
> 
> It can be helpful for debugging but usually nulling is not done when it's
> not really needed, because it is considered redundant.
> Currently it's not the usage in this module and in cma.c when calling
> rdma_destroy_id.

Well, 'not really needed' should be something simple to prove, and
this is not at all simple.

> >Isn't the list_for_each_safe version needed if list_del/kfree is called
> >within the body?
> No need for a safe version here.

Okay

Jason
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