From: Niels Dossche <dossche.niels@gmail.com>
Date: Mon, 28 Feb 2022 17:53:30 +0100
Subject: IB/rdmavt: add lock to call to rvt_error_qp to prevent a race
 condition
Patch-mainline: v5.18-rc2
Git-commit: 4d809f69695d4e7d1378b3a072fa9aef23123018
References: git-fixes

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>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/infiniband/sw/rdmavt/qp.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- 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);