[PATCH net 6/6] pds_core: make wait_context part of q_info

[Shannon Nelson]

Make the wait_context a full part of the q_info struct rather
than a stack variable that goes away after pdsc_adminq_post()
is done so that the context is still available after the wait
loop has given up.

There was a case where a slow development firmware caused
the adminq request to time out, but then later the FW finally
finished the request and sent the interrupt.  The handler tried
to complete_all() the completion context that had been created
on the stack in pdsc_adminq_post() but no longer existed.
This caused bad pointer usage, kernel crashes, and much wailing
and gnashing of teeth.

Fixes: 01ba61b55b20 ("pds_core: Add adminq processing and commands")
Signed-off-by: Shannon Nelson <shannon.nelson@xxxxxxx>
---
 drivers/net/ethernet/amd/pds_core/adminq.c | 23 +++++++---------------
 drivers/net/ethernet/amd/pds_core/core.h   |  7 ++++++-
 2 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/drivers/net/ethernet/amd/pds_core/adminq.c b/drivers/net/ethernet/amd/pds_core/adminq.c
index 2e840112efea..86a6371e5821 100644
--- a/drivers/net/ethernet/amd/pds_core/adminq.c
+++ b/drivers/net/ethernet/amd/pds_core/adminq.c
@@ -5,11 +5,6 @@
 
 #include "core.h"
 
-struct pdsc_wait_context {
-	struct pdsc_qcq *qcq;
-	struct completion wait_completion;
-};
-
 static int pdsc_process_notifyq(struct pdsc_qcq *qcq)
 {
 	union pds_core_notifyq_comp *comp;
@@ -112,7 +107,7 @@ void pdsc_process_adminq(struct pdsc_qcq *qcq)
 		/* Copy out the completion data */
 		memcpy(q_info->dest, comp, sizeof(*comp));
 
-		complete_all(&q_info->wc->wait_completion);
+		complete_all(&q_info->wc.wait_completion);
 
 		if (cq->tail_idx == cq->num_descs - 1)
 			cq->done_color = !cq->done_color;
@@ -162,8 +157,7 @@ irqreturn_t pdsc_adminq_isr(int irq, void *data)
 static int __pdsc_adminq_post(struct pdsc *pdsc,
 			      struct pdsc_qcq *qcq,
 			      union pds_core_adminq_cmd *cmd,
-			      union pds_core_adminq_comp *comp,
-			      struct pdsc_wait_context *wc)
+			      union pds_core_adminq_comp *comp)
 {
 	struct pdsc_queue *q = &qcq->q;
 	struct pdsc_q_info *q_info;
@@ -205,7 +199,6 @@ static int __pdsc_adminq_post(struct pdsc *pdsc,
 	/* Post the request */
 	index = q->head_idx;
 	q_info = &q->info[index];
-	q_info->wc = wc;
 	q_info->dest = comp;
 	memcpy(q_info->desc, cmd, sizeof(*cmd));
 
@@ -231,11 +224,8 @@ int pdsc_adminq_post(struct pdsc *pdsc,
 		     union pds_core_adminq_comp *comp,
 		     bool fast_poll)
 {
-	struct pdsc_wait_context wc = {
-		.wait_completion =
-			COMPLETION_INITIALIZER_ONSTACK(wc.wait_completion),
-	};
 	unsigned long poll_interval = 200;
+	struct pdsc_wait_context *wc;
 	unsigned long poll_jiffies;
 	unsigned long time_limit;
 	unsigned long time_start;
@@ -250,19 +240,20 @@ int pdsc_adminq_post(struct pdsc *pdsc,
 		return -ENXIO;
 	}
 
-	wc.qcq = &pdsc->adminqcq;
-	index = __pdsc_adminq_post(pdsc, &pdsc->adminqcq, cmd, comp, &wc);
+	index = __pdsc_adminq_post(pdsc, &pdsc->adminqcq, cmd, comp);
 	if (index < 0) {
 		err = index;
 		goto err_out;
 	}
 
+	wc = &pdsc->adminqcq.q.info[index].wc;
+	wc->wait_completion = COMPLETION_INITIALIZER_ONSTACK(wc->wait_completion);
 	time_start = jiffies;
 	time_limit = time_start + HZ * pdsc->devcmd_timeout;
 	do {
 		/* Timeslice the actual wait to catch IO errors etc early */
 		poll_jiffies = usecs_to_jiffies(poll_interval);
-		remaining = wait_for_completion_timeout(&wc.wait_completion,
+		remaining = wait_for_completion_timeout(&wc->wait_completion,
 							poll_jiffies);
 		if (remaining)
 			break;
diff --git a/drivers/net/ethernet/amd/pds_core/core.h b/drivers/net/ethernet/amd/pds_core/core.h
index 199473112c29..84fd814d7904 100644
--- a/drivers/net/ethernet/amd/pds_core/core.h
+++ b/drivers/net/ethernet/amd/pds_core/core.h
@@ -88,6 +88,11 @@ struct pdsc_buf_info {
 	u32 len;
 };
 
+struct pdsc_wait_context {
+	struct pdsc_qcq *qcq;
+	struct completion wait_completion;
+};
+
 struct pdsc_q_info {
 	union {
 		void *desc;
@@ -96,7 +101,7 @@ struct pdsc_q_info {
 	unsigned int bytes;
 	unsigned int nbufs;
 	struct pdsc_buf_info bufs[PDS_CORE_MAX_FRAGS];
-	struct pdsc_wait_context *wc;
+	struct pdsc_wait_context wc;
 	void *dest;
 };
 
-- 
2.17.1