fs/userfaultfd.c: disable irqs for fault_pending and event locks
When IOCB_CMD_POLL is used on a userfaultfd, aio_poll() disables IRQs and takes kioctx::ctx_lock, then userfaultfd_ctx::fd_wqh.lock. This may have to wait for userfaultfd_ctx::fd_wqh.lock to be released by userfaultfd_ctx_read(), which in turn can be waiting for userfaultfd_ctx::fault_pending_wqh.lock or userfaultfd_ctx::event_wqh.lock. But elsewhere the fault_pending_wqh and event_wqh locks are taken with IRQs enabled. Since the IRQ handler may take kioctx::ctx_lock, lockdep reports that a deadlock is possible. Fix it by always disabling IRQs when taking the fault_pending_wqh and event_wqh locks. Commit ae62c16e ("userfaultfd: disable irqs when taking the waitqueue lock") didn't fix this because it only accounted for the fd_wqh lock, not the other locks nested inside it. Link: http://lkml.kernel.org/r/20190627075004.21259-1-ebiggers@kernel.org Fixes: bfe4037e ("aio: implement IOCB_CMD_POLL") Signed-off-by: Eric Biggers <ebiggers@google.com> Reported-by: syzbot+fab6de82892b6b9c6191@syzkaller.appspotmail.com Reported-by: syzbot+53c0b767f7ca0dc0c451@syzkaller.appspotmail.com Reported-by: syzbot+a3accb352f9c22041cfa@syzkaller.appspotmail.com Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Christoph Hellwig <hch@lst.de> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: <stable@vger.kernel.org> [4.19+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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