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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>
This commit is contained in:
Andrea Arcangeli 2017-03-09 16:16:52 -08:00 committed by Linus Torvalds
parent dd0db88d80
commit 9a69a829f9
1 changed files with 7 additions and 2 deletions
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9
fs/userfaultfd.c
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@ -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;
}