[PATCH v6 00/11] arm64: untag user pointers passed to the kernel

Andrey Konovalov
2018-08-30T11:41:05Z

arm64 has a feature called Top Byte Ignore, which allows to embed pointer
tags into the top byte of each pointer. Userspace programs (such as
HWASan, a memory debugging tool [1]) might use this feature and pass
tagged user pointers to the kernel through syscalls or other interfaces.

This patch makes a few of the kernel interfaces accept tagged user
pointers. The kernel is already able to handle user faults with tagged
pointers and has the untagged_addr macro, which this patchset reuses.

Thanks!

[1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html

Changes in v6:
- Added annotations for user pointer casts found by sparse.
- Rebased onto 050cdc6c (4.19-rc1+).

Changes in v5:
- Added 3 new patches that add untagging to places found with static
analysis.
- Rebased onto 44c929e1 (4.18-rc8).

Changes in v4:
- Added a selftest for checking that passing tagged pointers to the
kernel succeeds.
- Rebased onto 81e97f013 (4.18-rc1+).

Changes in v3:
- Rebased onto e5c51f30 (4.17-rc6+).
- Added linux-arch@ to the list of recipients.

Changes in v2:
- Rebased onto 2d618bdf (4.17-rc3+).
- Removed excessive untagging in gup.c.
- Removed untagging pointers returned from __uaccess_mask_ptr.

Changes in v1:
- Rebased onto 4.17-rc1.

Changes in RFC v2:
- Added "#ifndef untagged_addr..." fallback in linux/uaccess.h instead of
defining it for each arch individually.
- Updated Documentation/arm64/tagged-pointers.txt.
- Dropped "mm, arm64: untag user addresses in memory syscalls".
- Rebased onto 3eb2ce82 (4.16-rc7).

Andrey Konovalov (11):
arm64: add type casts to untagged_addr macro
uaccess: add untagged_addr definition for other arches
arm64: untag user addresses in access_ok and __uaccess_mask_ptr
mm, arm64: untag user addresses in mm/gup.c
lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user
arm64: untag user address in __do_user_fault
fs, arm64: untag user address in copy_mount_options
usb, arm64: untag user addresses in devio
arm64: update Documentation/arm64/tagged-pointers.txt
selftests, arm64: add a selftest for passing tagged pointers to kernel
arm64: annotate user pointers casts detected by sparse

Documentation/arm64/tagged-pointers.txt | 5 +--
arch/arm64/include/asm/compat.h | 2 +-
arch/arm64/include/asm/uaccess.h | 16 ++++++----
arch/arm64/kernel/perf_callchain.c | 4 +--
arch/arm64/kernel/signal.c | 16 +++++-----
arch/arm64/kernel/signal32.c | 6 ++--
arch/arm64/mm/fault.c | 4 +--
block/compat_ioctl.c | 15 +++++----
drivers/ata/libata-scsi.c | 2 +-
drivers/block/loop.c | 2 +-
drivers/gpio/gpiolib.c | 8 +++--
drivers/input/evdev.c | 2 +-
drivers/media/dvb-core/dvb_frontend.c | 3 +-
drivers/media/v4l2-core/v4l2-compat-ioctl32.c | 9 +++---
drivers/mmc/core/block.c | 6 ++--
drivers/mtd/mtdchar.c | 2 +-
drivers/net/tap.c | 2 +-
drivers/net/tun.c | 2 +-
drivers/spi/spidev.c | 6 ++--
drivers/tty/tty_ioctl.c | 3 +-
drivers/tty/vt/vt_ioctl.c | 5 +--
drivers/usb/core/devio.c | 10 ++++--
drivers/vfio/vfio.c | 6 ++--
drivers/video/fbdev/core/fbmem.c | 4 +--
drivers/xen/gntdev.c | 6 ++--
drivers/xen/privcmd.c | 4 +--
fs/aio.c | 2 +-
fs/autofs/dev-ioctl.c | 3 +-
fs/autofs/root.c | 2 +-
fs/binfmt_elf.c | 10 +++---
fs/btrfs/ioctl.c | 2 +-
fs/compat_ioctl.c | 32 ++++++++++---------
fs/ext2/ioctl.c | 2 +-
fs/ext4/ioctl.c | 2 +-
fs/fat/file.c | 3 +-
fs/fuse/file.c | 2 +-
fs/namespace.c | 2 +-
fs/readdir.c | 4 +--
fs/signalfd.c | 10 +++---
include/linux/mm.h | 2 +-
include/linux/pagemap.h | 8 ++---
include/linux/socket.h | 2 +-
include/linux/uaccess.h | 4 +++
ipc/shm.c | 4 +--
kernel/futex.c | 6 ++--
kernel/futex_compat.c | 2 +-
kernel/power/user.c | 2 +-
kernel/signal.c | 2 +-
lib/iov_iter.c | 16 +++++-----
lib/strncpy_from_user.c | 4 ++-
lib/strnlen_user.c | 6 ++--
lib/test_kasan.c | 2 +-
mm/gup.c | 4 +++
mm/memory.c | 2 +-
mm/migrate.c | 4 +--
mm/process_vm_access.c | 13 ++++----
net/bluetooth/hidp/sock.c | 2 +-
net/compat.c | 12 ++++---
sound/core/control_compat.c | 5 +--
sound/core/pcm_native.c | 5 +--
sound/core/timer_compat.c | 3 +-
tools/testing/selftests/arm64/.gitignore | 1 +
tools/testing/selftests/arm64/Makefile | 11 +++++++
.../testing/selftests/arm64/run_tags_test.sh | 12 +++++++
tools/testing/selftests/arm64/tags_test.c | 19 +++++++++++
65 files changed, 232 insertions(+), 147 deletions(-)
create mode 100644 tools/testing/selftests/arm64/.gitignore
create mode 100644 tools/testing/selftests/arm64/Makefile
create mode 100755 tools/testing/selftests/arm64/run_tags_test.sh
create mode 100644 tools/testing/selftests/arm64/tags_test.c

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2.19.0.rc0.228.g281dcd1b4d0-goog