4.19-stable review patch. If anyone has any objections, please let me know.
------------------ From: Christoph Hellwig <[email protected]> commit ae62c16e105a869524afcf8a07ee85c5ae5d0479 upstream. userfaultfd contains howe-grown locking of the waitqueue lock, and does not disable interrupts. This relies on the fact that no one else takes it from interrupt context and violates an invariat of the normal waitqueue locking scheme. With aio poll it is easy to trigger other locks that disable interrupts (or are called from interrupt context). Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Christoph Hellwig <[email protected]> Reviewed-by: Andrea Arcangeli <[email protected]> Reviewed-by: Andrew Morton <[email protected]> Cc: <[email protected]> [4.19.x] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/userfaultfd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1026,7 +1026,7 @@ static ssize_t userfaultfd_ctx_read(stru struct userfaultfd_ctx *fork_nctx = NULL; /* always take the fd_wqh lock before the fault_pending_wqh lock */ - spin_lock(&ctx->fd_wqh.lock); + spin_lock_irq(&ctx->fd_wqh.lock); __add_wait_queue(&ctx->fd_wqh, &wait); for (;;) { set_current_state(TASK_INTERRUPTIBLE); @@ -1112,13 +1112,13 @@ static ssize_t userfaultfd_ctx_read(stru ret = -EAGAIN; break; } - spin_unlock(&ctx->fd_wqh.lock); + spin_unlock_irq(&ctx->fd_wqh.lock); schedule(); - spin_lock(&ctx->fd_wqh.lock); + spin_lock_irq(&ctx->fd_wqh.lock); } __remove_wait_queue(&ctx->fd_wqh, &wait); __set_current_state(TASK_RUNNING); - spin_unlock(&ctx->fd_wqh.lock); + spin_unlock_irq(&ctx->fd_wqh.lock); if (!ret && msg->event == UFFD_EVENT_FORK) { ret = resolve_userfault_fork(ctx, fork_nctx, msg);
