Re: [PATCH v2 3/5] mm: Make PR_MDWE_REFUSE_EXEC_GAIN an unsigned long

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On 17.05.23 17:03, Florent Revest wrote:
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@xxxxxxxxxxxx>
Suggested-by: Alexey Izbyshev <izbyshev@xxxxxxxxx>
---
  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

Both are changing existing uapi, so you'll already have existing user space using the old values, that your kernel code has to deal with no?

--
Thanks,

David / dhildenb





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