From 9d95aa4bada24be35bb94827a55e1d6e243d866e Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Wed, 2 Aug 2017 13:32:15 -0700 Subject: userfaultfd_zeropage: return -ENOSPC in case mm has gone In the non-cooperative userfaultfd case, the process exit may race with outstanding mcopy_atomic called by the uffd monitor. Returning -ENOSPC instead of -EINVAL when mm is already gone will allow uffd monitor to distinguish this case from other error conditions. Unfortunately I overlooked userfaultfd_zeropage when updating userfaultd_copy(). Link: http://lkml.kernel.org/r/1501136819-21857-1-git-send-email-rppt@linux.vnet.ibm.com Fixes: 96333187ab162 ("userfaultfd_copy: return -ENOSPC in case mm has gone") Signed-off-by: Mike Rapoport Cc: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Pavel Emelyanov Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index cadcd12a3d35..2d8c2d848668 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1643,6 +1643,8 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, uffdio_zeropage.range.len); mmput(ctx->mm); + } else { + return -ENOSPC; } if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) return -EFAULT; -- cgit v1.2.3-59-g8ed1b From 5a18b64e3f02125be1c0ef777501ae38aafe2a24 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Wed, 2 Aug 2017 13:32:24 -0700 Subject: userfaultfd: non-cooperative: flush event_wqh at release time There may still be threads waiting on event_wqh at the time the userfault file descriptor is closed. Flush the events wait-queue to prevent waiting threads from hanging. Link: http://lkml.kernel.org/r/1501398127-30419-1-git-send-email-rppt@linux.vnet.ibm.com Fixes: 9cd75c3cd4c3d ("userfaultfd: non-cooperative: add ability to report non-PF events from uffd descriptor") Signed-off-by: Mike Rapoport Cc: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Pavel Emelyanov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 2d8c2d848668..06ea26b8c996 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -854,6 +854,9 @@ wakeup: __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range); spin_unlock(&ctx->fault_pending_wqh.lock); + /* Flush pending events that may still wait on event_wqh */ + wake_up_all(&ctx->event_wqh); + wake_up_poll(&ctx->fd_wqh, POLLHUP); userfaultfd_ctx_put(ctx); return 0; -- cgit v1.2.3-59-g8ed1b From e86b298bebf7e799e4b7232e9135799f1947552e Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Thu, 10 Aug 2017 15:24:32 -0700 Subject: userfaultfd: replace ENOSPC with ESRCH in case mm has gone during copy/zeropage When the process exit races with outstanding mcopy_atomic, it would be better to return ESRCH error. When such race occurs the process and it's mm are going away and returning "no such process" to the uffd monitor seems better fit than ENOSPC. Link: http://lkml.kernel.org/r/1502111545-32305-1-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport Suggested-by: Michal Hocko Acked-by: Michal Hocko Cc: Andrea Arcangeli Cc: "Dr. David Alan Gilbert" Cc: Pavel Emelyanov Cc: Mike Kravetz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/userfaultfd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/userfaultfd.c') diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 06ea26b8c996..b0d5897bc4e6 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1600,7 +1600,7 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx, uffdio_copy.len); mmput(ctx->mm); } else { - return -ENOSPC; + return -ESRCH; } if (unlikely(put_user(ret, &user_uffdio_copy->copy))) return -EFAULT; @@ -1647,7 +1647,7 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, uffdio_zeropage.range.len); mmput(ctx->mm); } else { - return -ENOSPC; + return -ESRCH; } if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) return -EFAULT; -- cgit v1.2.3-59-g8ed1b