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userfaultfd: non-cooperative: report all available features to userland

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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 <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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrea Arcangeli 2017-02-22 15:42:24 -08:00 committed by Linus Torvalds
parent 9cd75c3cd4
commit 656031445d
1 changed files with 7 additions and 4 deletions
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11
fs/userfaultfd.c
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@ -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;