[PATCH 4.19 087/168] RDMA/rxe: Prevent access to wr->next ptr afrer wr is posted to send queue

[Greg Kroah-Hartman]

From: Mikhail Malygin <m.malygin@xxxxxxxxx>

[ Upstream commit 5f0b2a6093a4d9aab093964c65083fe801ef1e58 ]

rxe_post_send_kernel() iterates over linked list of wr's, until the
wr->next ptr is NULL.  However if we've got an interrupt after last wr is
posted, control may be returned to the code after send completion callback
is executed and wr memory is freed.

As a result, wr->next pointer may contain incorrect value leading to
panic. Store the wr->next on the stack before posting it.

Fixes: 8700e3e7c485 ("Soft RoCE driver")
Link: https://lore.kernel.org/r/20200716190340.23453-1-m.malygin@xxxxxxxxx
Signed-off-by: Mikhail Malygin <m.malygin@xxxxxxxxx>
Signed-off-by: Sergey Kojushev <s.kojushev@xxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/infiniband/sw/rxe/rxe_verbs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/sw/rxe/rxe_verbs.c b/drivers/infiniband/sw/rxe/rxe_verbs.c
index f5b1e0ad61420..3a94eb5edcf90 100644
--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -733,6 +733,7 @@ static int rxe_post_send_kernel(struct rxe_qp *qp, const struct ib_send_wr *wr,
 	unsigned int mask;
 	unsigned int length = 0;
 	int i;
+	struct ib_send_wr *next;
 
 	while (wr) {
 		mask = wr_opcode_mask(wr->opcode, qp);
@@ -749,6 +750,8 @@ static int rxe_post_send_kernel(struct rxe_qp *qp, const struct ib_send_wr *wr,
 			break;
 		}
 
+		next = wr->next;
+
 		length = 0;
 		for (i = 0; i < wr->num_sge; i++)
 			length += wr->sg_list[i].length;
@@ -759,7 +762,7 @@ static int rxe_post_send_kernel(struct rxe_qp *qp, const struct ib_send_wr *wr,
 			*bad_wr = wr;
 			break;
 		}
-		wr = wr->next;
+		wr = next;
 	}
 
 	rxe_run_task(&qp->req.task, 1);
-- 
2.25.1