[PATCH for-rc] RDMA/efa: Fix race between admin command timeout and completion

[Yonatan Nachum <ynachum@amazon.com>]

When an admin command times out, there is a potential race between the
interrupt handler processing the completion and the timeout path
releasing the completion context. The interrupt handler may observe the
command as still submitted and attempt to complete it while the timeout
path is concurrently freeing the context.

Fix this by introducing a timed-out state in the completion context. On
timeout, both the polling and interrupt wait paths set the status to
timed-out under the CQ lock before returning. The completion handler
only process commands in submitted state, eliminating the race.

Fixes: 0420e542569b ("RDMA/efa: Implement functions that submit and complete admin commands")
Reviewed-by: Tom Sela <tomsela@amazon.com>
Signed-off-by: Yonatan Nachum <ynachum@amazon.com>
---
 drivers/infiniband/hw/efa/efa_com.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/hw/efa/efa_com.c b/drivers/infiniband/hw/efa/efa_com.c
index 583b1cf0d721..a91de9283b6b 100644
--- a/drivers/infiniband/hw/efa/efa_com.c
+++ b/drivers/infiniband/hw/efa/efa_com.c
@@ -41,6 +41,7 @@ enum efa_cmd_status {
 	EFA_CMD_ALLOCATED,
 	EFA_CMD_SUBMITTED,
 	EFA_CMD_COMPLETED,
+	EFA_CMD_TIMED_OUT,
 };
 
 struct efa_comp_ctx {
@@ -605,6 +606,10 @@ static int efa_com_wait_and_process_admin_cq_polling(struct efa_comp_ctx *comp_c
 			break;
 
 		if (time_is_before_jiffies(timeout)) {
+			spin_lock_irqsave(&aq->cq.lock, flags);
+			comp_ctx->status = EFA_CMD_TIMED_OUT;
+			spin_unlock_irqrestore(&aq->cq.lock, flags);
+
 			ibdev_err_ratelimited(
 				aq->efa_dev,
 				"Wait for completion (polling) timeout\n");
@@ -639,7 +644,6 @@ static int efa_com_wait_and_process_admin_cq_interrupts(struct efa_comp_ctx *com
 	if (comp_ctx->status == EFA_CMD_SUBMITTED) {
 		spin_lock_irqsave(&aq->cq.lock, flags);
 		efa_com_handle_admin_completion(aq);
-		spin_unlock_irqrestore(&aq->cq.lock, flags);
 
 		atomic64_inc(&aq->stats.no_completion);
 
@@ -660,6 +664,9 @@ static int efa_com_wait_and_process_admin_cq_interrupts(struct efa_comp_ctx *com
 				comp_ctx->cmd_id, aq->sq.pc, aq->sq.cc,
 				aq->cq.cc);
 
+		comp_ctx->status = EFA_CMD_TIMED_OUT;
+		spin_unlock_irqrestore(&aq->cq.lock, flags);
+
 		clear_bit(EFA_AQ_STATE_RUNNING_BIT, &aq->state);
 		return -ETIME;
 	}
-- 
2.50.1