[V7,0/7] fixes for virtual address update

Message

Steven Sistare Dec. 20, 2022, 8:39 p.m. UTC

Fix bugs in the interfaces that allow the underlying memory object of an
iova range to be mapped in a new address space.  They allow userland to
indefinitely block vfio mediated device kernel threads, and do not
propagate the locked_vm count to a new mm.  Also fix a pre-existing bug
that allows locked_vm underflow.

The fixes impose restrictions that eliminate waiting conditions, so
revert the dead code:
  commit 898b9eaeb3fe ("vfio/type1: block on invalid vaddr")
  commit 487ace134053 ("vfio/type1: implement notify callback")
  commit ec5e32940cc9 ("vfio: iommu driver notify callback")

Changes in V2 (thanks Alex):
  * do not allow group attach while vaddrs are invalid
  * add patches to delete dead code
  * add WARN_ON for never-should-happen conditions
  * check for changed mm in unmap.
  * check for vfio_lock_acct failure in remap

Changes in V3 (ditto!):
  * return errno at WARN_ON sites, and make it unique
  * correctly check for dma task mm change
  * change dma owner to current when vaddr is updated
  * add Fixes to commit messages
  * refactored new code in vfio_dma_do_map

Changes in V4:
  * misc cosmetic changes

Changes in V5 (thanks Jason and Kevin):
  * grab mm and use it for locked_vm accounting
  * separate patches for underflow and restoring locked_vm
  * account for reserved pages
  * improve error messages

Changes in V6:
  * drop "count reserved pages" patch
  * add "track locked_vm" patch
  * grab current->mm not group_leader->mm
  * simplify vfio_change_dma_owner
  * fix commit messages

Changes in v7:
  * compare current->mm not group_leader->mm (missed one)
  * misc cosmetic changes

Steve Sistare (7):
  vfio/type1: exclude mdevs from VFIO_UPDATE_VADDR
  vfio/type1: prevent underflow of locked_vm via exec()
  vfio/type1: track locked_vm per dma
  vfio/type1: restore locked_vm
  vfio/type1: revert "block on invalid vaddr"
  vfio/type1: revert "implement notify callback"
  vfio: revert "iommu driver notify callback"

 drivers/vfio/container.c        |   5 -
 drivers/vfio/vfio.h             |   7 --
 drivers/vfio/vfio_iommu_type1.c | 226 ++++++++++++++++++----------------------
 include/uapi/linux/vfio.h       |  15 +--
 4 files changed, 111 insertions(+), 142 deletions(-)