[PATCH 5/5] net: atlantic: verify hw_head_ is reasonable

[Grant Grundler]

Bounds check hw_head index to verify it lies within the TX buffer ring.

Unexpected values of hw_head may cause aq_ring_tx_clean to double
dev_kfree_skb_any already cleaned parts of the ring.

Reported-by: Aashay Shringarpure <aashay@xxxxxxxxxx>
Reported-by: Yi Chou <yich@xxxxxxxxxx>
Reported-by: Shervin Oloumi <enlightened@xxxxxxxxxx>
Signed-off-by: Grant Grundler <grundler@xxxxxxxxxxxx>
---
 .../aquantia/atlantic/hw_atl/hw_atl_b0.c      | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c b/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c
index e72b9d86f6ad..9b6b93bb3e86 100644
--- a/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c
+++ b/drivers/net/ethernet/aquantia/atlantic/hw_atl/hw_atl_b0.c
@@ -889,6 +889,27 @@ int hw_atl_b0_hw_ring_tx_head_update(struct aq_hw_s *self,
 		err = -ENXIO;
 		goto err_exit;
 	}
+
+	/* Validate that the new hw_head_ is reasonable. */
+	if (hw_head_ >= ring->size) {
+		err = -ENXIO;
+		goto err_exit;
+	}
+
+	if (ring->sw_head >= ring->sw_tail) {
+		/* Head index hasn't wrapped around to below tail index. */
+		if (hw_head_ < ring->sw_head && hw_head_ >= ring->sw_tail) {
+			err = -ENXIO;
+			goto err_exit;
+		}
+	} else {
+		/* Head index has wrapped around and is below tail index. */
+		if (hw_head_ < ring->sw_head || hw_head_ >= ring->sw_tail) {
+			err = -ENXIO;
+			goto err_exit;
+		}
+	}
+
 	ring->hw_head = hw_head_;
 	err = aq_hw_err_from_flags(self);
 
-- 
2.36.0.rc0.470.gd361397f0d-goog