[PATCH 5.15 178/277] IB/rdmavt: add lock to call to rvt_error_qp to prevent a race condition

[Greg Kroah-Hartman]

From: Niels Dossche <dossche.niels@xxxxxxxxx>

[ Upstream commit 4d809f69695d4e7d1378b3a072fa9aef23123018 ]

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@xxxxxxxxx
Signed-off-by: Niels Dossche <dossche.niels@xxxxxxxxx>
Acked-by: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/infiniband/sw/rdmavt/qp.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
index ae50b56e8913..8ef112f883a7 100644
--- a/drivers/infiniband/sw/rdmavt/qp.c
+++ b/drivers/infiniband/sw/rdmavt/qp.c
@@ -3190,7 +3190,11 @@ void rvt_ruc_loopback(struct rvt_qp *sqp)
 	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);
-- 
2.35.1