From: Andrea Arcangeli <aarcange@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Michael Rapoport <RAPOPORT@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/userfaultfd.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff -puN fs/userfaultfd.c~userfaultfd-non-cooperative-report-all-available-features-to-userland fs/userfaultfd.c --- a/fs/userfaultfd.c~userfaultfd-non-cooperative-report-all-available-features-to-userland +++ a/fs/userfaultfd.c @@ -1285,6 +1285,7 @@ static int userfaultfd_api(struct userfa 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 userfa 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; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
