1 files changed, 32 insertions, 22 deletions

diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
index f24dd5223926..5aef2be2d027 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.c
+++ b/drivers/gpu/drm/xe/xe_guc_ct.c
@@ -8,6 +8,7 @@
 #include <linux/bitfield.h>
 #include <linux/circ_buf.h>
 #include <linux/delay.h>
+#include <linux/fault-inject.h>
 
 #include <kunit/static_stub.h>
 
@@ -182,7 +183,7 @@ int xe_guc_ct_init(struct xe_guc_ct *ct)
 	spin_lock_init(&ct->fast_lock);
 	xa_init(&ct->fence_lookup);
 	INIT_WORK(&ct->g2h_worker, g2h_worker_func);
-	INIT_DELAYED_WORK(&ct->safe_mode_worker,  safe_mode_worker_func);
+	INIT_DELAYED_WORK(&ct->safe_mode_worker, safe_mode_worker_func);
 	init_waitqueue_head(&ct->wq);
 	init_waitqueue_head(&ct->g2h_fence_wq);
 
@@ -209,6 +210,7 @@ int xe_guc_ct_init(struct xe_guc_ct *ct)
 	ct->state = XE_GUC_CT_STATE_DISABLED;
 	return 0;
 }
+ALLOW_ERROR_INJECTION(xe_guc_ct_init, ERRNO); /* See xe_pci_probe() */
 
 #define desc_read(xe_, guc_ctb__, field_)			\
 	xe_map_rd_field(xe_, &guc_ctb__->desc, 0,		\
@@ -667,16 +669,12 @@ static int __guc_ct_send_locked(struct xe_guc_ct *ct, const u32 *action,
 		num_g2h = 1;
 
 		if (g2h_fence_needs_alloc(g2h_fence)) {
-			void *ptr;
-
 			g2h_fence->seqno = next_ct_seqno(ct, true);
-			ptr = xa_store(&ct->fence_lookup,
-				       g2h_fence->seqno,
-				       g2h_fence, GFP_ATOMIC);
-			if (IS_ERR(ptr)) {
-				ret = PTR_ERR(ptr);
+			ret = xa_err(xa_store(&ct->fence_lookup,
+					      g2h_fence->seqno, g2h_fence,
+					      GFP_ATOMIC));
+			if (ret)
 				goto out;
-			}
 		}
 
 		seqno = g2h_fence->seqno;
@@ -852,7 +850,7 @@ static bool retry_failure(struct xe_guc_ct *ct, int ret)
 #define ct_alive(ct)	\
 	(xe_guc_ct_enabled(ct) && !ct->ctbs.h2g.info.broken && \
 	 !ct->ctbs.g2h.info.broken)
-	if (!wait_event_interruptible_timeout(ct->wq, ct_alive(ct),  HZ * 5))
+	if (!wait_event_interruptible_timeout(ct->wq, ct_alive(ct), HZ * 5))
 		return false;
 #undef ct_alive
 
@@ -879,14 +877,11 @@ retry:
 retry_same_fence:
 	ret = guc_ct_send(ct, action, len, 0, 0, &g2h_fence);
 	if (unlikely(ret == -ENOMEM)) {
-		void *ptr;
-
 		/* Retry allocation /w GFP_KERNEL */
-		ptr = xa_store(&ct->fence_lookup,
-			       g2h_fence.seqno,
-			       &g2h_fence, GFP_KERNEL);
-		if (IS_ERR(ptr))
-			return PTR_ERR(ptr);
+		ret = xa_err(xa_store(&ct->fence_lookup, g2h_fence.seqno,
+				      &g2h_fence, GFP_KERNEL));
+		if (ret)
+			return ret;
 
 		goto retry_same_fence;
 	} else if (unlikely(ret)) {
@@ -897,22 +892,32 @@ retry_same_fence:
 			goto retry_same_fence;
 
 		if (!g2h_fence_needs_alloc(&g2h_fence))
-			xa_erase_irq(&ct->fence_lookup, g2h_fence.seqno);
+			xa_erase(&ct->fence_lookup, g2h_fence.seqno);
 
 		return ret;
 	}
 
 	ret = wait_event_timeout(ct->g2h_fence_wq, g2h_fence.done, HZ);
+
+	/*
+	 * Ensure we serialize with completion side to prevent UAF with fence going out of scope on
+	 * the stack, since we have no clue if it will fire after the timeout before we can erase
+	 * from the xa. Also we have some dependent loads and stores below for which we need the
+	 * correct ordering, and we lack the needed barriers.
+	 */
+	mutex_lock(&ct->lock);
 	if (!ret) {
-		xe_gt_err(gt, "Timed out wait for G2H, fence %u, action %04x",
-			  g2h_fence.seqno, action[0]);
-		xa_erase_irq(&ct->fence_lookup, g2h_fence.seqno);
+		xe_gt_err(gt, "Timed out wait for G2H, fence %u, action %04x, done %s",
+			  g2h_fence.seqno, action[0], str_yes_no(g2h_fence.done));
+		xa_erase(&ct->fence_lookup, g2h_fence.seqno);
+		mutex_unlock(&ct->lock);
 		return -ETIME;
 	}
 
 	if (g2h_fence.retry) {
 		xe_gt_dbg(gt, "H2G action %#x retrying: reason %#x\n",
 			  action[0], g2h_fence.reason);
+		mutex_unlock(&ct->lock);
 		goto retry;
 	}
 	if (g2h_fence.fail) {
@@ -921,7 +926,12 @@ retry_same_fence:
 		ret = -EIO;
 	}
 
-	return ret > 0 ? response_buffer ? g2h_fence.response_len : g2h_fence.response_data : ret;
+	if (ret > 0)
+		ret = response_buffer ? g2h_fence.response_len : g2h_fence.response_data;
+
+	mutex_unlock(&ct->lock);
+
+	return ret;
 }
 
 /**