From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Laight Date: Sat, 16 May 2020 15:11:40 +0000 Subject: [Ocfs2-devel] [PATCH 27/33] sctp: export sctp_setsockopt_bindx In-Reply-To: <129070.1589556002@warthog.procyon.org.uk> References: <20200514062820.GC8564@lst.de> <20200513062649.2100053-1-hch@lst.de> <20200513062649.2100053-28-hch@lst.de> <20200513180058.GB2491@localhost.localdomain> <129070.1589556002@warthog.procyon.org.uk> Message-ID: <05d946ae948946158dbfcbc07939b799@AcuMS.aculab.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: 'David Howells' , Christoph Hellwig Cc: Marcelo Ricardo Leitner , Eric Dumazet , "linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-sctp-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-afs-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "drbd-dev-cunTk1MwBs8qoQakbn7OcQ@public.gmane.org" , "linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "rds-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org" , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "cluster-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org" , Alexey Kuznetsov , "linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Jakub Kicinski , ceph-devel-u79uwXL29TY@public.gmane.org From: David Howells > Sent: 15 May 2020 16:20 > Christoph Hellwig 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. Yes, it also simplifies all the compat code. And there is a BPF test in setsockopt that also wants to pass on a kernel buffer. I'm willing to sit and write the patch. Quoting from a post I made later on Friday. Basically: This patch sequence (to be written) does the following: Patch 1: Change __sys_setsockopt() to allocate a kernel buffer, copy the data into it then call set_fs(KERNEL_DS). An on-stack buffer (say 64 bytes) will be used for small transfers. Patch 2: The same for __sys_getsockopt(). Patch 3: Compat setsockopt. Patch 4: Compat getsockopt. Patch 5: Remove the user copies from the global socket options code. Patches 6 to n-1; Remove the user copies from the per-protocol code. Patch n: Remove the set_fs(KERNEL_DS) from the entry points. This should be bisectable. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)