[PATCH 0/1] userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK

Hi,

A while ago Andy noticed [1] that UFFD_FEATURE_EVENT_FORK used by an
unprivileged user may have security implications.

As the first step of the solution the following patch limits the
availably of UFFD_FEATURE_EVENT_FORK only for those having CAP_SYS_PTRACE.

The usage of CAP_SYS_PTRACE ensures compatibility with CRIU.

Yet, if there are other users of non-cooperative userfaultfd that run
without CAP_SYS_PTRACE, they would be broken :(

[1] https://lore.kernel.org/lkml/CALCETrWY+5ynDct7eU_nDUqx=okQvjm=Y5wJvA4ahBja=CQXGw@mail.gmail.com (local)

Mike Rapoport (1):
  userfaultfd: require CAP_SYS_PTRACE for UFFD_FEATURE_EVENT_FORK

 fs/userfaultfd.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

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2.7.4