On Thu, Jun 29, 2023 at 4:34 PM jeffxu@chromium.org wrote:
From: Jeff Xu jeffxu@google.com
Please ignore this, I resent V3 with a cover letter.
Add documentation for sysctl vm.memfd_noexec
Link:https://lore.kernel.org/linux-mm/CABi2SkXUX_QqTQ10Yx9bBUGpN1wByOi_=gZU6WEy5a... Reported-by: Dominique Martinet asmadeus@codewreck.org Signed-off-by: Jeff Xu jeffxu@google.com
Documentation/admin-guide/sysctl/vm.rst | 30 +++++++++++++++++++++++++ 1 file changed, 30 insertions(+)
diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 45ba1f4dc004..621588041a9e 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -424,6 +424,36 @@ e.g., up to one or two maps per allocation.
The default value is 65530.
+memfd_noexec: +============= +This pid namespaced sysctl controls memfd_create().
+The new MFD_NOEXEC_SEAL and MFD_EXEC flags of memfd_create() allows +application to set executable bit at creation time.
+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 default value is 0.
+Once set, it can't be downgraded at runtime, i.e. 2=>1, 1=>0 +are denied.
+This is pid namespaced sysctl, child processes inherit the parent +process's memfd_noexec at the time of fork. Changes to the parent +process after fork are not automatically propagated to the child +process.
memory_failure_early_kill:
-- 2.41.0.255.g8b1d071c50-goog