On Wed, 14 Aug 2019 18:09:36 +0300 Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> wrote: > On Mon, Aug 12, 2019 at 02:19:24PM -0700, Andrew Morton wrote: > > Hi, Andrew > > >On Mon, 12 Aug 2019 15:43:26 +0300 Ivan Khoronzhuk <ivan.khoronzhuk@xxxxxxxxxx> wrote: > > > >> The AF_XDP sockets umem mapping interface uses XDP_UMEM_PGOFF_FILL_RING > >> and XDP_UMEM_PGOFF_COMPLETION_RING offsets. The offsets seems like are > >> established already and are part of configuration interface. > >> > >> But for 32-bit systems, while AF_XDP socket configuration, the values > >> are to large to pass maximum allowed file size verification. > >> The offsets can be tuned ofc, but instead of changing existent > >> interface - extend max allowed file size for sockets. > > > > > >What are the implications of this? That all code in the kernel which > >handles mapped sockets needs to be audited (and tested) for correctly > >handling mappings larger than 4G on 32-bit machines? Has that been > > That's to allow only offset to be passed, mapping length is less than 4Gb. > I have verified all list of mmap for sockets and all of them contain dummy > cb sock_no_mmap() except the following: > > xsk_mmap() > tcp_mmap() > packet_mmap() > > xsk_mmap() - it's what this fix is needed for. > tcp_mmap() - doesn't have obvious issues with pgoff - no any references on it. > packet_mmap() - return -EINVAL if it's even set. Great, thanks. > > >done? Are we confident that we aren't introducing user-visible buggy > >behaviour into unsuspecting legacy code? > > > >Also... what are the user-visible runtime effects of this change? > >Please send along a paragraph which explains this, for the changelog. > >Does this patch fix some user-visible problem? If so, should be code > >be backported into -stable kernels? > It should go to linux-next, no one has been using it till this patch > with 32 bits as w/o this fix af_xdp sockets can't be used at all. > It unblocks af_xdp socket usage for 32bit systems. > > > That's example of potential next commit message: > Subject: mm: mmap: increase sockets maximum memory size pgoff for 32bits > > The AF_XDP sockets umem mapping interface uses XDP_UMEM_PGOFF_FILL_RING > and XDP_UMEM_PGOFF_COMPLETION_RING offsets. These offsets are established > already and are part of the configuration interface. > > But for 32-bit systems, using AF_XDP socket configuration, these values > are too large to pass the maximum allowed file size verification. The > offsets can be tuned off, but instead of changing the existing interface, > let's extend the max allowed file size for sockets. > > No one has been using it till this patch with 32 bits as w/o this fix > af_xdp sockets can't be used at all, so it unblocks af_xdp socket usage > for 32bit systems. > > All list of mmap cbs for sockets were verified on side effects and > all of them contain dummy cb - sock_no_mmap() at this moment, except the > following: > > xsk_mmap() - it's what this fix is needed for. > tcp_mmap() - doesn't have obvious issues with pgoff - no any references on it. > packet_mmap() - return -EINVAL if it's even set. > > ... > > Is it ok to be replicated in PATCH v2 or this explanation is enough here > to use v1? I have replaced the changlog in my tree with the above, thanks.
