Re: [PATCH rdma-rc] IB/mlx5: Fix use-after-free error while accessing ev_file pointer

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On Thu, 2019-08-08 at 15:34 +0000, Jason Gunthorpe wrote:
> On Thu, Aug 08, 2019 at 06:32:00PM +0300, Yishai Hadas wrote:
> > > > diff --git a/drivers/infiniband/hw/mlx5/devx.c
> > > > b/drivers/infiniband/hw/mlx5/devx.c
> > > > index 2d1b3d9609d9..af5bbb35c058 100644
> > > > +++ b/drivers/infiniband/hw/mlx5/devx.c
> > > > @@ -2644,12 +2644,13 @@ static int devx_async_event_close(struct
> > > > inode *inode, struct file *filp)
> > > >   	struct devx_async_event_file *ev_file = filp-
> > > > >private_data;
> > > 
> > > This line is wrong, it should be
> > > 
> > >    	struct devx_async_event_file *ev_file =
> > > container_of(struct
> > >   	                   devx_async_event_file, filp-
> > > >private_data, uobj);
> > 
> > You suggested the below 2 lines instead of the above one line,
> > correct ? as
> > struct devx_async_event_file wraps uobj as its first field this is
> > logically
> > equal, agree ?
> 
> Yes, it is wrong only in the use of the type system, the private_data
> void * should only ever be cast to a ib_uobject.
> 
> > struct ib_uobject *uobj = filp->private_data;
> 
> This could be done with a cast
> 
> > > It is also a bit redundant to store the mlx5_ib_dev in the
> > > devx_async_event_file as uobj->ucontext->dev is the same pointer.
> > >  
> > Post hot unplug uobj->ucontext might not be accessible, isn't it ?
> > Current code should be fine for that.
> 
> That is the other kind of weird thing, all this destruction could be
> done on unplug..
> 
> > Are we fine to take this patch ?
> 
> Yes

Thanks, applied to for-rc.

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Doug Ledford <dledford@xxxxxxxxxx>
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