IB/rdmavt: add lock to call to rvt_error_qp to prevent a race condition

The documentation of the function rvt_error_qp says both r_lock and s_lock
need to be held when calling that function.  It also asserts using lockdep
that both of those locks are held.  However, the commit I referenced in
Fixes accidentally makes the call to rvt_error_qp in rvt_ruc_loopback no
longer covered by r_lock.  This results in the lockdep assertion failing
and also possibly in a race condition.

Fixes: d757c60eca9b ("IB/rdmavt: Fix concurrency panics in QP post_send and modify to error")
Link: https://lore.kernel.org/r/20220228165330.41546-1-dossche.niels@gmail.com
Signed-off-by: Niels Dossche <dossche.niels@gmail.com>
Acked-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
index ae50b56..8ef112f 100644 (file)
--- a/drivers/infiniband/sw/rdmavt/qp.c
+++ b/drivers/infiniband/sw/rdmavt/qp.c
@@ -3190,7 +3190,11 @@ serr_no_r_lock:
        spin_lock_irqsave(&sqp->s_lock, flags);
        rvt_send_complete(sqp, wqe, send_status);
        if (sqp->ibqp.qp_type == IB_QPT_RC) {
-               int lastwqe = rvt_error_qp(sqp, IB_WC_WR_FLUSH_ERR);
+               int lastwqe;
+
+               spin_lock(&sqp->r_lock);
+               lastwqe = rvt_error_qp(sqp, IB_WC_WR_FLUSH_ERR);
+               spin_unlock(&sqp->r_lock);
 
                sqp->s_flags &= ~RVT_S_BUSY;
                spin_unlock_irqrestore(&sqp->s_lock, flags);