[RFC PATCH 01/13] fs/userfaultfd: fix wrong error code on WP & !VM_MAYWRITE

[Nadav Amit <nadav.amit@gmail.com>]

From: Nadav Amit <namit@vmware.com>

It is possible to get an EINVAL error instead of EPERM if the following
test vm_flags have VM_UFFD_WP but do not have VM_MAYWRITE, as "ret" is
overwritten since commit cab350afcbc9 ("userfaultfd: hugetlbfs: allow
registration of ranges containing huge pages").

Fix it.

Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: io-uring@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Fixes: cab350afcbc9 ("userfaultfd: hugetlbfs: allow registration of ranges containing huge pages")
Signed-off-by: Nadav Amit <namit@vmware.com>
---
 fs/userfaultfd.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 000b457ad087..c8ed4320370e 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1364,6 +1364,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 			if (end & (vma_hpagesize - 1))
 				goto out_unlock;
 		}
+		ret = -EPERM;
 		if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE))
 			goto out_unlock;
 
-- 
2.25.1