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Commit 65603144 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds
Browse files

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: default avatarAndrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9cd75c3c

fs/userfaultfd.c

+7 −4
Original line number Diff line number Diff line
@@ -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;