From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f196.google.com ([209.85.216.196]:45082 "EHLO mail-qt0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726792AbeILB2J (ORCPT ); Tue, 11 Sep 2018 21:28:09 -0400 MIME-Version: 1.0 References: <20180908142837.2819693-1-arnd@arndb.de> <20180908142837.2819693-6-arnd@arndb.de> <20180909041114.GD19965@ZenIV.linux.org.uk> In-Reply-To: <20180909041114.GD19965@ZenIV.linux.org.uk> From: Arnd Bergmann Date: Tue, 11 Sep 2018 22:26:54 +0200 Message-ID: Subject: Re: [PATCH 06/11] compat_ioctl: remove /dev/random commands To: Al Viro Cc: "Theodore Ts'o" , gregkh , Linux Kernel Mailing List , Linux FS-devel Mailing List , linux-s390 , Martin Schwidefsky , Heiko Carstens Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Sun, Sep 9, 2018 at 6:12 AM Al Viro 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(). 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. 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. Arnd