This is a note to let you know that I've just added the patch titled
mm: make PR_MDWE_REFUSE_EXEC_GAIN an unsigned long
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-make-pr_mdwe_refuse_exec_gain-an-unsigned-long.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 0da668333fb07805c2836d5d50e26eda915b24a1 Mon Sep 17 00:00:00 2001
From: Florent Revest <revest@xxxxxxxxxxxx>
Date: Mon, 28 Aug 2023 17:08:56 +0200
Subject: mm: make PR_MDWE_REFUSE_EXEC_GAIN an unsigned long
From: Florent Revest <revest@xxxxxxxxxxxx>
commit 0da668333fb07805c2836d5d50e26eda915b24a1 upstream.
Defining a prctl flag as an int is a footgun because on a 64 bit machine
and with a variadic implementation of prctl (like in musl and glibc), when
used directly as a prctl argument, it can get casted to long with garbage
upper bits which would result in unexpected behaviors.
This patch changes the constant to an unsigned long to eliminate that
possibilities. This does not break UAPI.
I think that a stable backport would be "nice to have": to reduce the
chances that users build binaries that could end up with garbage bits in
their MDWE prctl arguments. We are not aware of anyone having yet
encountered this corner case with MDWE prctls but a backport would reduce
the likelihood it happens, since this sort of issues has happened with
other prctls. But If this is perceived as a backporting burden, I suppose
we could also live without a stable backport.
Link: https://lkml.kernel.org/r/20230828150858.393570-5-revest@xxxxxxxxxxxx
Fixes: b507808ebce2 ("mm: implement memory-deny-write-execute as a prctl")
Signed-off-by: Florent Revest <revest@xxxxxxxxxxxx>
Suggested-by: Alexey Izbyshev <izbyshev@xxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Ayush Jain <ayush.jain3@xxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Cc: Joey Gouly <joey.gouly@xxxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Szabolcs Nagy <Szabolcs.Nagy@xxxxxxx>
Cc: Topi Miettinen <toiwoton@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/prctl.h | 2 +-
tools/include/uapi/linux/prctl.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -283,7 +283,7 @@ struct prctl_mm_map {
/* Memory deny write / execute */
#define PR_SET_MDWE 65
-# define PR_MDWE_REFUSE_EXEC_GAIN 1
+# define PR_MDWE_REFUSE_EXEC_GAIN (1UL << 0)
#define PR_GET_MDWE 66
--- a/tools/include/uapi/linux/prctl.h
+++ b/tools/include/uapi/linux/prctl.h
@@ -283,7 +283,7 @@ struct prctl_mm_map {
/* Memory deny write / execute */
#define PR_SET_MDWE 65
-# define PR_MDWE_REFUSE_EXEC_GAIN 1
+# define PR_MDWE_REFUSE_EXEC_GAIN (1UL << 0)
#define PR_GET_MDWE 66
Patches currently in stable-queue which might be from revest@xxxxxxxxxxxx are
queue-6.6/mm-make-pr_mdwe_refuse_exec_gain-an-unsigned-long.patch
