On Mon, 28 Aug 2023 17:08:56 +0200 Florent Revest <[email protected]> wrote:
> 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.
>
> Fixes: b507808ebce2 ("mm: implement memory-deny-write-execute as a prctl")
> Cc: [email protected]
> Signed-off-by: Florent Revest <[email protected]>
> Suggested-by: Alexey Izbyshev <[email protected]>
> Reviewed-by: David Hildenbrand <[email protected]>
> Reviewed-by: Kees Cook <[email protected]>
> Acked-by: Catalin Marinas <[email protected]>
Why is this being offered to -stable? Does it fix any known problem?
On Fri, Sep 22, 2023 at 3:29 AM Andrew Morton <[email protected]> wrote:
>
> On Mon, 28 Aug 2023 17:08:56 +0200 Florent Revest <[email protected]> wrote:
>
> > 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.
> >
> > Fixes: b507808ebce2 ("mm: implement memory-deny-write-execute as a prctl")
> > Cc: [email protected]
> > Signed-off-by: Florent Revest <[email protected]>
> > Suggested-by: Alexey Izbyshev <[email protected]>
> > Reviewed-by: David Hildenbrand <[email protected]>
> > Reviewed-by: Kees Cook <[email protected]>
> > Acked-by: Catalin Marinas <[email protected]>
>
> Why is this being offered to -stable? Does it fix any known problem?
The background for this was discussed in these threads:
v1: https://lore.kernel.org/all/[email protected]/
v2: https://lore.kernel.org/all/[email protected]/
Cc-ing stable was suggested by David and Alexey:
> On Mon, May 22, 2023 at 8:58 PM Alexey Izbyshev <[email protected]> wrote:
> > On 2023-05-22 19:22, David Hildenbrand wrote:
> > > Which raises the question if we want to tag this here with a "Fixes"
> > > and eventually cc stable (hmm ...)?
> >
> > Yes, IMO the faster we propagate this change, the better.
>
> Okay, will do
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.