libfs: set SB_I_NOEXEC and SB_I_NODEV in init_pseudo()

[PATCH v3 0/2] libfs: set SB_I_NOEXEC and SB_I_NODEV in init_pseudo()
Posted by John Hubbard 4 days, 5 hours ago
This began as a one-line dma-buf fix for a path_noexec() warning added
by commit 1e7ab6f67824 ("anon_inode: rework assertions"). Christoph
pointed out that the fix belongs higher up: a pseudo filesystem has no
reason not to set SB_I_NOEXEC by default. This series does that.

  * Patch 1 sets both flags in init_pseudo(), so every pseudo
    filesystem gets them. This is the only patch that changes a flag,
    and the only one with Fixes:/Cc: stable.

  * Patch 2 drops the assignments that are now redundant in the callers
    that set them by hand.

Most callers already set one or both flags. I audited every
init_pseudo() caller. Here is what patch 1 actually changes for each.
The only visible effect is on dma-buf, where SB_I_NOEXEC silences the
warning. SB_I_NODEV is never consulted on these SB_NOUSER mounts, and
none of the callers that gain SB_I_NOEXEC are executed from.

  caller                       had        patch 1 adds
  ---------------------------  --------   --------------
  fs/anon_inodes.c             both       nothing new
  mm/secretmem.c               both       nothing new
  virt/kvm/guest_memfd.c       both       nothing new
  fs/nsfs.c                    both       nothing new
  fs/pidfs.c                   both       nothing new
  fs/aio.c                     NOEXEC     NODEV
  drivers/dma-buf/dma-buf.c    neither    NOEXEC + NODEV
  net/socket.c                 neither    NOEXEC + NODEV
  fs/pipe.c                    neither    NOEXEC + NODEV
  kernel/resource.c            neither    NOEXEC + NODEV
  fs/erofs/super.c             neither    NOEXEC + NODEV
  fs/btrfs/tests/...           neither    NOEXEC + NODEV
  drivers/vfio/vfio_main.c     neither    NOEXEC + NODEV
  drivers/gpu/drm/drm_drv.c    neither    NOEXEC + NODEV
  drivers/dax/super.c          neither    NOEXEC + NODEV
  block/bdev.c                 neither    NOEXEC + NODEV

John Hubbard (2):
  libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
  libfs: drop redundant SB_I_NOEXEC/SB_I_NODEV in init_pseudo() callers

 fs/aio.c               | 1 -
 fs/anon_inodes.c       | 2 --
 fs/libfs.c             | 1 +
 fs/nsfs.c              | 1 -
 fs/pidfs.c             | 2 --
 mm/secretmem.c         | 2 --
 virt/kvm/guest_memfd.c | 2 --
 7 files changed, 1 insertion(+), 10 deletions(-)


base-commit: ba3e43a9e601636f5edb54e259a74f96ca3b8fd8
-- 
2.54.0