From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Date: Sat, 16 May 2020 08:36:52 -0700 Subject: [Ocfs2-devel] [PATCH 27/33] sctp: export sctp_setsockopt_bindx In-Reply-To: <05d946ae948946158dbfcbc07939b799@AcuMS.aculab.com> 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> <05d946ae948946158dbfcbc07939b799@AcuMS.aculab.com> Message-ID: <20200516153652.GM16070@bombadil.infradead.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Laight Cc: 'David Howells' , Christoph Hellwig , Marcelo Ricardo Leitner , "linux-nvme@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-sctp@vger.kernel.org" , "target-devel@vger.kernel.org" , "linux-afs@lists.infradead.org" , "drbd-dev@lists.linbit.com" , "linux-cifs@vger.kernel.org" , "rds-devel@oss.oracle.com" , "linux-rdma@vger.kernel.org" , "cluster-devel@redhat.com" , Jakub Kicinski , linux-block@vger.kernel On Sat, May 16, 2020 at 03:11:40PM +0000, David Laight wrote: > 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. I appreciate your dedication to not publishing the source code to your kernel module, but Christoph's patch series is actually better. It's typesafe rather than passing void pointers around.