On Thu, Nov 07, 2019 at 05:00:23PM -0800, Andrew Morton wrote: > On Thu, 7 Nov 2019 14:53:54 -0500 "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx> wrote: > > > F_SEAL_FUTURE_WRITE has unexpected behavior when used with MAP_PRIVATE: > > A private mapping created after the memfd file that gets sealed with > > F_SEAL_FUTURE_WRITE loses the copy-on-write at fork behavior, meaning > > children and parent share the same memory, even though the mapping is > > private. > > That sounds fairly serious. Should this be backported into -stable kernels? Yes, it should be. The F_SEAL_FUTURE_WRITE feature was introduced in v5.1 so v5.3.x stable kernels would need a backport. I can submit a backport tomorrow unless we are Ok with stable automatically picking it up (I believe the stable folks "auto select" fixes which should detect this is a fix since I have said it is a fix in the subject line). thanks, - Joel
