net: atlantic: Avoid out-of-bounds indexing

UBSAN warnings are observed on atlantic driver:
[ 294.432996] UBSAN: array-index-out-of-bounds in /build/linux-Qow4fL/linux-5.15.0/drivers/net/ethernet/aquantia/atlantic/aq_nic.c:484:48
[ 294.433695] index 8 is out of range for type 'aq_vec_s *[8]'

The ring is dereferenced right before breaking out the loop, to prevent
that from happening, only use the index in the loop to fix the issue.

BugLink: https://bugs.launchpad.net/bugs/1958770Tested-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Reviewed-by: Igor Russkikh <irusskikh@marvell.com>
Link: https://lore.kernel.org/r/20220408022204.16815-1-kai.heng.feng@canonical.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/aquantia/atlantic/aq_nic.c

@@ -486,8 +486,8 @@ int aq_nic_start(struct aq_nic_s *self)
 	if (err < 0)
 		goto err_exit;
 
-	for (i = 0U, aq_vec = self->aq_vec[0];
-		self->aq_vecs > i; ++i, aq_vec = self->aq_vec[i]) {
+	for (i = 0U; self->aq_vecs > i; ++i) {
+		aq_vec = self->aq_vec[i];
 		err = aq_vec_start(aq_vec);
 		if (err < 0)
 			goto err_exit;
@@ -517,8 +517,8 @@ int aq_nic_start(struct aq_nic_s *self)
 		mod_timer(&self->polling_timer, jiffies +
 			  AQ_CFG_POLLING_TIMER_INTERVAL);
 	} else {
-		for (i = 0U, aq_vec = self->aq_vec[0];
-			self->aq_vecs > i; ++i, aq_vec = self->aq_vec[i]) {
+		for (i = 0U; self->aq_vecs > i; ++i) {
+			aq_vec = self->aq_vec[i];
 			err = aq_pci_func_alloc_irq(self, i, self->ndev->name,
 						    aq_vec_isr, aq_vec,
 						    aq_vec_get_affinity_mask(aq_vec));

drivers/net/ethernet/aquantia/atlantic/aq_vec.c

@@ -43,8 +43,8 @@ static int aq_vec_poll(struct napi_struct *napi, int budget)
 	if (!self) {
 		err = -EINVAL;
 	} else {
-		for (i = 0U, ring = self->ring[0];
-			self->tx_rings > i; ++i, ring = self->ring[i]) {
+		for (i = 0U; self->tx_rings > i; ++i) {
+			ring = self->ring[i];
 			u64_stats_update_begin(&ring[AQ_VEC_RX_ID].stats.rx.syncp);
 			ring[AQ_VEC_RX_ID].stats.rx.polls++;
 			u64_stats_update_end(&ring[AQ_VEC_RX_ID].stats.rx.syncp);
@@ -182,8 +182,8 @@ int aq_vec_init(struct aq_vec_s *self, const struct aq_hw_ops *aq_hw_ops,
 	self->aq_hw_ops = aq_hw_ops;
 	self->aq_hw = aq_hw;
 
-	for (i = 0U, ring = self->ring[0];
-		self->tx_rings > i; ++i, ring = self->ring[i]) {
+	for (i = 0U; self->tx_rings > i; ++i) {
+		ring = self->ring[i];
 		err = aq_ring_init(&ring[AQ_VEC_TX_ID], ATL_RING_TX);
 		if (err < 0)
 			goto err_exit;
@@ -224,8 +224,8 @@ int aq_vec_start(struct aq_vec_s *self)
 	unsigned int i = 0U;
 	int err = 0;
 
-	for (i = 0U, ring = self->ring[0];
-		self->tx_rings > i; ++i, ring = self->ring[i]) {
+	for (i = 0U; self->tx_rings > i; ++i) {
+		ring = self->ring[i];
 		err = self->aq_hw_ops->hw_ring_tx_start(self->aq_hw,
 							&ring[AQ_VEC_TX_ID]);
 		if (err < 0)
@@ -248,8 +248,8 @@ void aq_vec_stop(struct aq_vec_s *self)
 	struct aq_ring_s *ring = NULL;
 	unsigned int i = 0U;
 
-	for (i = 0U, ring = self->ring[0];
-		self->tx_rings > i; ++i, ring = self->ring[i]) {
+	for (i = 0U; self->tx_rings > i; ++i) {
+		ring = self->ring[i];
 		self->aq_hw_ops->hw_ring_tx_stop(self->aq_hw,
 						 &ring[AQ_VEC_TX_ID]);
 
@@ -268,8 +268,8 @@ void aq_vec_deinit(struct aq_vec_s *self)
 	if (!self)
 		goto err_exit;
 
-	for (i = 0U, ring = self->ring[0];
-		self->tx_rings > i; ++i, ring = self->ring[i]) {
+	for (i = 0U; self->tx_rings > i; ++i) {
+		ring = self->ring[i];
 		aq_ring_tx_clean(&ring[AQ_VEC_TX_ID]);
 		aq_ring_rx_deinit(&ring[AQ_VEC_RX_ID]);
 	}
@@ -297,8 +297,8 @@ void aq_vec_ring_free(struct aq_vec_s *self)
 	if (!self)
 		goto err_exit;
 
-	for (i = 0U, ring = self->ring[0];
-		self->tx_rings > i; ++i, ring = self->ring[i]) {
+	for (i = 0U; self->tx_rings > i; ++i) {
+		ring = self->ring[i];
 		aq_ring_free(&ring[AQ_VEC_TX_ID]);
 		if (i < self->rx_rings)
 			aq_ring_free(&ring[AQ_VEC_RX_ID]);