linux-kernel - [RFC PATCH 01/13] fs/userfaultfd: fix wrong error code on WP & !VM

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Date:   Sat, 28 Nov 2020 16:45:36 -0800
From:   Nadav Amit <nadav.amit@...il.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     Nadav Amit <namit@...are.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Jens Axboe <axboe@...nel.dk>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [RFC PATCH 01/13] fs/userfaultfd: fix wrong error code on WP & !VM_MAYWRITE

From: Nadav Amit <namit@...are.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@...cle.com>
Cc: Jens Axboe <axboe@...nel.dk>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>
Cc: io-uring@...r.kernel.org
Cc: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org
Fixes: cab350afcbc9 ("userfaultfd: hugetlbfs: allow registration of ranges containing huge pages")
Signed-off-by: Nadav Amit <namit@...are.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