From 656031445d5a855e1c13b291dedae32579d0f3f2 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Wed, 22 Feb 2017 15:42:24 -0800 Subject: [PATCH] userfaultfd: non-cooperative: report all available features to userland This will allow userland to probe all features available in the kernel. It will however only enable the requested features in the open userfaultfd context. Link: http://lkml.kernel.org/r/20161216144821.5183-8-aarcange@redhat.com Signed-off-by: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Hillf Danton Cc: Michael Rapoport Cc: Mike Kravetz Cc: Mike Rapoport Cc: Pavel Emelyanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index b5074a344635..87d31921b66c 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1285,6 +1285,7 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, struct uffdio_api uffdio_api; void __user *buf = (void __user *)arg; int ret; + __u64 features; ret = -EINVAL; if (ctx->state != UFFD_STATE_WAIT_API) @@ -1292,21 +1293,23 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, ret = -EFAULT; if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) goto out; - if (uffdio_api.api != UFFD_API || - (uffdio_api.features & ~UFFD_API_FEATURES)) { + features = uffdio_api.features; + if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) { memset(&uffdio_api, 0, sizeof(uffdio_api)); if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) goto out; ret = -EINVAL; goto out; } - uffdio_api.features &= UFFD_API_FEATURES; + /* report all available features and ioctls to userland */ + uffdio_api.features = UFFD_API_FEATURES; uffdio_api.ioctls = UFFD_API_IOCTLS; ret = -EFAULT; if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) goto out; ctx->state = UFFD_STATE_RUNNING; - ctx->features = uffd_ctx_features(uffdio_api.features); + /* only enable the requested features for this uffd context */ + ctx->features = uffd_ctx_features(features); ret = 0; out: return ret;