We should fail uffd-wp registration immediately if the arch does not even have
CONFIG_HAVE_ARCH_USERFAULTFD_WP defined. That'll block also relevant ioctls on
e.g. UFFDIO_WRITEPROTECT because that'll check against VM_UFFD_WP, which can
only be applied with a success registration.
Remove the WP feature bit too for those archs when handling UFFDIO_API ioctl.
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
fs/userfaultfd.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 14f92285d04f8..5dd78238cc156 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1304,8 +1304,12 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
vm_flags = 0;
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
vm_flags |= VM_UFFD_MISSING;
- if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP)
+ if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
+#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+ goto out;
+#endif
vm_flags |= VM_UFFD_WP;
+ }
if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
goto out;
@@ -1942,6 +1946,9 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
uffdio_api.features = UFFD_API_FEATURES;
#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
uffdio_api.features &= ~UFFD_FEATURE_MINOR_HUGETLBFS;
+#endif
+#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+ uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
#endif
uffdio_api.ioctls = UFFD_API_IOCTLS;
ret = -EFAULT;
--
2.26.2
