Re: [PATCH v2 1/2] Add UFFD_USER_MODE_ONLY

2020-08-25 Thread Lokesh Gidra
On Mon, Aug 24, 2020 at 5:32 AM Sebastian Andrzej Siewior wrote: > > On 2020-08-21 18:40:17 [-0700], Lokesh Gidra wrote: > > --- a/fs/userfaultfd.c > > +++ b/fs/userfaultfd.c > > @@ -1966,6 +1969,7 @@ static void init_once_userfaultfd_ctx(void *mem) > > > > SYSCALL_DEFINE1(userfaultfd, int, flags

Re: [PATCH v2 1/2] Add UFFD_USER_MODE_ONLY

2020-08-24 Thread Sebastian Andrzej Siewior
On 2020-08-21 18:40:17 [-0700], Lokesh Gidra wrote: > --- a/fs/userfaultfd.c > +++ b/fs/userfaultfd.c > @@ -1966,6 +1969,7 @@ static void init_once_userfaultfd_ctx(void *mem) > > SYSCALL_DEFINE1(userfaultfd, int, flags) > { > + static const int uffd_flags = UFFD_USER_MODE_ONLY; > stru

[PATCH v2 1/2] Add UFFD_USER_MODE_ONLY

2020-08-21 Thread Lokesh Gidra
userfaultfd handles page faults from both user and kernel code. Add a new UFFD_USER_MODE_ONLY flag for userfaultfd(2) that makes the resulting userfaultfd object refuse to handle faults from kernel mode, treating these faults as if SIGBUS were always raised, causing the kernel code to fail with EFA