On Tue, 11 Sep 2018 22:26:54 +0200 Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Sun, Sep 9, 2018 at 6:12 AM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > On Sat, Sep 08, 2018 at 04:28:12PM +0200, Arnd Bergmann wrote: > > > These are all handled by the random driver, so instead of listing > > > each ioctl, we can just use the same function to deal with both > > > native and compat commands. > > > > Umm... I don't think it's right - > > > > > .unlocked_ioctl = random_ioctl, > > > + .compat_ioctl = random_ioctl, > > > > > > ->compat_ioctl() gets called in > > error = f.file->f_op->compat_ioctl(f.file, cmd, arg); > > so you do *NOT* get compat_ptr() for those - they have to do it on their > > own. It's not hard to provide a proper compat_ioctl() instance for that > > one, but this is not it. What you need in drivers/char/random.c part of > > that one is something like > > Looping in some s390 folks. > > As you suggested in another reply, I had a look at what other drivers > do the same thing and have only pointer arguments. I created a > patch to move them all over to using a new helper function that > adds the compat_ptr(), and arrived at > > drivers/android/binder.c | 2 +- > drivers/crypto/qat/qat_common/adf_ctl_drv.c | 2 +- > drivers/dma-buf/dma-buf.c | 4 +--- > drivers/dma-buf/sw_sync.c | 2 +- > drivers/dma-buf/sync_file.c | 2 +- > drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 2 +- > drivers/hid/hidraw.c | 4 +--- > drivers/iio/industrialio-core.c | 2 +- > drivers/infiniband/core/uverbs_main.c | 4 ++-- > drivers/media/rc/lirc_dev.c | 4 +--- > drivers/mfd/cros_ec_dev.c | 4 +--- > drivers/misc/vmw_vmci/vmci_host.c | 2 +- > drivers/nvdimm/bus.c | 4 ++-- > drivers/nvme/host/core.c | 6 +++--- > drivers/pci/switch/switchtec.c | 2 +- > drivers/platform/x86/wmi.c | 2 +- > drivers/rpmsg/rpmsg_char.c | 4 ++-- > drivers/s390/char/sclp_ctl.c | 8 ++------ > drivers/s390/char/vmcp.c | 2 ++---- > drivers/s390/cio/chsc_sch.c | 8 ++------ > drivers/sbus/char/display7seg.c | 2 +- > drivers/sbus/char/envctrl.c | 4 +--- > drivers/scsi/3w-xxxx.c | 4 +--- > drivers/scsi/cxlflash/main.c | 2 +- > drivers/scsi/esas2r/esas2r_main.c | 2 +- > drivers/scsi/pmcraid.c | 4 +--- > drivers/staging/android/ion/ion.c | 4 +--- > drivers/staging/vme/devices/vme_user.c | 2 +- > drivers/tee/tee_core.c | 2 +- > drivers/usb/class/cdc-wdm.c | 2 +- > drivers/usb/class/usbtmc.c | 4 +--- > drivers/video/fbdev/ps3fb.c | 2 +- > drivers/video/fbdev/sis/sis_main.c | 4 +--- > drivers/virt/fsl_hypervisor.c | 2 +- > fs/btrfs/super.c | 2 +- > fs/ceph/dir.c | 2 +- > fs/ceph/file.c | 2 +- > fs/fuse/dev.c | 2 +- > fs/notify/fanotify/fanotify_user.c | 2 +- > fs/userfaultfd.c | 2 +- > net/rfkill/core.c | 2 +- > 41 files changed, 48 insertions(+), 76 deletions(-) > > Out of those, there are only a few that may get used on s390, > in particular at most infiniband/uverbs, nvme, nvdimm, > btrfs, ceph, fuse, fanotify and userfaultfd. > [Note: there are three s390 drivers in the list, which use > a different method: they check in_compat_syscall() from > a shared handler to decide whether to do compat_ptr(). Using in_compat_syscall() seems to be a good solution, no? > According to my memory from when I last worked on this, > the compat_ptr() is mainly a safeguard for legacy binaries > that got created with ancient C compilers (or compilers for > something other than C) and might leave the high bit set > in a pointer, but modern C compilers (gcc-3+) won't ever > do that. And compat_ptr clears the upper 32-bit of the register. If the register is loaded to e.g. "lr" or "l" there will be junk in the 4 upper bytes. > You are probably right about /dev/random, which could be > used in lots of weird code, but I wonder to what degree we > need to worry about it for the rest. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.
