6.6-stable review patch. If anyone has any objections, please let me know.
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From: Florent Revest revest@chromium.org
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@chromium.org Fixes: b507808ebce2 ("mm: implement memory-deny-write-execute as a prctl") Signed-off-by: Florent Revest revest@chromium.org Suggested-by: Alexey Izbyshev izbyshev@ispras.ru Reviewed-by: David Hildenbrand david@redhat.com Reviewed-by: Kees Cook keescook@chromium.org Acked-by: Catalin Marinas catalin.marinas@arm.com Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: Ayush Jain ayush.jain3@amd.com Cc: Greg Thelen gthelen@google.com Cc: Joey Gouly joey.gouly@arm.com Cc: KP Singh kpsingh@kernel.org Cc: Mark Brown broonie@kernel.org Cc: Michal Hocko mhocko@suse.com Cc: Peter Xu peterx@redhat.com Cc: Ryan Roberts ryan.roberts@arm.com Cc: Szabolcs Nagy Szabolcs.Nagy@arm.com Cc: Topi Miettinen toiwoton@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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