linux-kernel - [PATCH v2 3/5] mm: Make PR_MDWE_REFUSE_EXEC

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Date:   Wed, 17 May 2023 17:03:19 +0200
From:   Florent Revest <revest@...omium.org>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     akpm@...ux-foundation.org, catalin.marinas@....com,
        anshuman.khandual@....com, joey.gouly@....com, mhocko@...e.com,
        keescook@...omium.org, david@...hat.com, peterx@...hat.com,
        izbyshev@...ras.ru, broonie@...nel.org, szabolcs.nagy@....com,
        kpsingh@...nel.org, gthelen@...gle.com, toiwoton@...il.com,
        Florent Revest <revest@...omium.org>
Subject: [PATCH v2 3/5] mm: Make PR_MDWE_REFUSE_EXEC_GAIN an unsigned long

Alexey pointed out that defining a prctl flag as an int is a footgun
because, under some circumstances, when used as a flag to prctl, it can
be casted to long with garbage upper bits which would result in
unexpected behaviors.

This patch changes the constant to a UL to eliminate these
possibilities.

Signed-off-by: Florent Revest <revest@...omium.org>
Suggested-by: Alexey Izbyshev <izbyshev@...ras.ru>
---
 include/uapi/linux/prctl.h       | 2 +-
 tools/include/uapi/linux/prctl.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index f23d9a16507f..6e9af6cbc950 100644
--- 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
 
diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h
index 759b3f53e53f..6e6563e97fef 100644
--- 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
 
-- 
2.40.1.606.ga4b1b128d6-goog