On Fri, May 15, 2020 at 04:20:02PM +0100, David Howells wrote: > Christoph Hellwig <hch@xxxxxx> wrote: > > > > The advantage on using kernel_setsockopt here is that sctp module will > > > only be loaded if dlm actually creates a SCTP socket. With this > > > change, sctp will be loaded on setups that may not be actually using > > > it. It's a quite big module and might expose the system. > > > > True. Not that the intent is to kill kernel space callers of setsockopt, > > as I plan to remove the set_fs address space override used for it. > > For getsockopt, does it make sense to have the core kernel load optval/optlen > into a buffer before calling the protocol driver? Then the driver need not > see the userspace pointer at all. > > Similar could be done for setsockopt - allocate a buffer of the size requested > by the user inside the kernel and pass it into the driver, then copy the data > back afterwards. I did look into that initially. The problem is that tons of sockopts entirely ignore optlen and just use a fixed size. So I fear that there could be tons of breakage if we suddently respect it. Otherwise that would be a pretty nice way to handle the situation.
