From 9a69a829f9b656c2a220d65a94ecf7b5887c5da1 Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@redhat.com>
Date: Thu, 9 Mar 2017 16:16:52 -0800
Subject: [PATCH] userfaultfd: non-cooperative: robustness check
Similar to the handle_userfault() case, also make sure to never attempt
to send any event past the PF_EXITING point of no return.
This is purely a robustness check.
Link: http://lkml.kernel.org/r/20170224181957.19736-3-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/userfaultfd.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 16d0cc600fa9..668bbbd2e04d 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -530,8 +530,13 @@ int handle_userfault(struct vm_fault *vmf, unsigned long reason)
static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
struct userfaultfd_wait_queue *ewq)
{
- int ret = 0;
+ int ret;
+
+ ret = -1;
+ if (WARN_ON_ONCE(current->flags & PF_EXITING))
+ goto out;
+ ret = 0;
ewq->ctx = ctx;
init_waitqueue_entry(&ewq->wq, current);
@@ -566,7 +571,7 @@ static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
* ctx may go away after this if the userfault pseudo fd is
* already released.
*/
-
+out:
userfaultfd_ctx_put(ctx);
return ret;
}
--
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