mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC

The new MFD_NOEXEC_SEAL and MFD_EXEC flags allows application to set
executable bit at creation time (memfd_create).

When MFD_NOEXEC_SEAL is set, memfd is created without executable bit
(mode:0666), and sealed with F_SEAL_EXEC, so it can't be chmod to be
executable (mode: 0777) after creation.

when MFD_EXEC flag is set, memfd is created with executable bit
(mode:0777), this is the same as the old behavior of memfd_create.

The new pid namespaced sysctl vm.memfd_noexec has 3 values:
0: memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL acts like
        MFD_EXEC was set.
1: memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL acts like
        MFD_NOEXEC_SEAL was set.
2: memfd_create() without MFD_NOEXEC_SEAL will be rejected.

The sysctl allows finer control of memfd_create for old-software that
doesn't set the executable bit, for example, a container with
vm.memfd_noexec=1 means the old-software will create non-executable memfd
by default.  Also, the value of memfd_noexec is passed to child namespace
at creation time.  For example, if the init namespace has
vm.memfd_noexec=2, all its children namespaces will be created with 2.

[[email protected]: add stub functions to fix build]
[[email protected]: remove unneeded register_pid_ns_ctl_table_vm() stub, per Jeff]
[[email protected]: s/pr_warn_ratelimited/pr_warn_once/, per review]
[[email protected]: fix CONFIG_SYSCTL=n warning]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jeff Xu <[email protected]>
Co-developed-by: Daniel Verkamp <[email protected]>
Signed-off-by: Daniel Verkamp <[email protected]>
Reported-by: kernel test robot <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Cc: David Herrmann <[email protected]>
Cc: Dmitry Torokhov <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Jorge Lucangeli Obes <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions