[net PATCH v3 0/4] ravb Ethernet driver bugfixes

[net PATCH v3 0/4] ravb Ethernet driver bugfixes

[Paul Barker]

These patches fix bugs found during recent work on the ravb driver.

Patches 1 & 2 affect the R-Car code paths so have been tested on an
R-Car M3N Salvator-XS board - this is the only R-Car board I currently
have access to.

Patches 2, 3 & 4 affect the GbEth code paths so have been tested on
RZ/G2L and RZ/G2UL SMARC EVK boards.

Changes v2->v3:
  * Incorporate feedback from Niklas and add Reviewed-by tag to patch
    "net: ravb: Count packets instead of descriptors in R-Car RX path".
Changes v1->v2:
  * Fixed typos in commit message of patch
    "net: ravb: Allow RX loop to move past DMA mapping errors".
  * Added Sergey's Reviewed-by tags.
  * Expanded Cc list as Patchwork complained that I had missed people.
  * Trimmed the call trace in accordance with the docs [1] in patch
    "net: ravb: Fix GbEth jumbo packet RX checksum handling".

[1]: https://docs.kernel.org/process/submitting-patches.html#backtraces-in-commit-messages

Paul Barker (4):
  net: ravb: Count packets instead of descriptors in R-Car RX path
  net: ravb: Allow RX loop to move past DMA mapping errors
  net: ravb: Fix GbEth jumbo packet RX checksum handling
  net: ravb: Fix RX byte accounting for jumbo packets

 drivers/net/ethernet/renesas/ravb_main.c | 68 +++++++++++-------------
 1 file changed, 32 insertions(+), 36 deletions(-)


base-commit: 75ce9506ee3dc66648a7d74ab3b0acfa364d6d43
-- 
2.39.2

[net PATCH v3 1/4] net: ravb: Count packets instead of descriptors in R-Car RX path

[Paul Barker]

The units of "work done" in the RX path should be packets instead of
descriptors.

Descriptors which are used by the hardware to record error conditions or
are empty in the case of a DMA mapping error should not count towards
our RX work budget.

Also make the limit variable unsigned as it can never be negative.

Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
---
Changes v2->v3:
  * Use unsigned int for `limit` and `i` variables.
  * Add Niklas' Reviewed-by tag.
Changes v1->v2:
  * Add Sergey's Reviewed-by tag.

 drivers/net/ethernet/renesas/ravb_main.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index ba01c8cc3c90..7d231d011bff 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -892,29 +892,24 @@ static bool ravb_rx_rcar(struct net_device *ndev, int *quota, int q)
 	struct ravb_private *priv = netdev_priv(ndev);
 	const struct ravb_hw_info *info = priv->info;
 	int entry = priv->cur_rx[q] % priv->num_rx_ring[q];
-	int boguscnt = (priv->dirty_rx[q] + priv->num_rx_ring[q]) -
-			priv->cur_rx[q];
 	struct net_device_stats *stats = &priv->stats[q];
 	struct ravb_ex_rx_desc *desc;
+	unsigned int limit, i;
 	struct sk_buff *skb;
 	dma_addr_t dma_addr;
 	struct timespec64 ts;
+	int rx_packets = 0;
 	u8  desc_status;
 	u16 pkt_len;
-	int limit;
 
-	boguscnt = min(boguscnt, *quota);
-	limit = boguscnt;
+	limit = priv->dirty_rx[q] + priv->num_rx_ring[q] - priv->cur_rx[q];
 	desc = &priv->rx_ring[q].ex_desc[entry];
-	while (desc->die_dt != DT_FEMPTY) {
+	for (i = 0; i < limit && rx_packets < *quota && desc->die_dt != DT_FEMPTY; i++) {
 		/* Descriptor type must be checked before all other reads */
 		dma_rmb();
 		desc_status = desc->msc;
 		pkt_len = le16_to_cpu(desc->ds_cc) & RX_DS;
 
-		if (--boguscnt < 0)
-			break;
-
 		/* We use 0-byte descriptors to mark the DMA mapping errors */
 		if (!pkt_len)
 			continue;
@@ -960,7 +955,7 @@ static bool ravb_rx_rcar(struct net_device *ndev, int *quota, int q)
 			if (ndev->features & NETIF_F_RXCSUM)
 				ravb_rx_csum(skb);
 			napi_gro_receive(&priv->napi[q], skb);
-			stats->rx_packets++;
+			rx_packets++;
 			stats->rx_bytes += pkt_len;
 		}
 
@@ -995,9 +990,9 @@ static bool ravb_rx_rcar(struct net_device *ndev, int *quota, int q)
 		desc->die_dt = DT_FEMPTY;
 	}
 
-	*quota -= limit - (++boguscnt);
-
-	return boguscnt <= 0;
+	stats->rx_packets += rx_packets;
+	*quota -= rx_packets;
+	return *quota == 0;
 }
 
 /* Packet receive function for Ethernet AVB */
-- 
2.39.2

[net PATCH v3 2/4] net: ravb: Allow RX loop to move past DMA mapping errors

[Paul Barker]

The RX loops in ravb_rx_gbeth() and ravb_rx_rcar() skip to the next loop
iteration if a zero-length descriptor is seen (indicating a DMA mapping
error). However, the current RX descriptor index `priv->cur_rx[q]` was
incremented at the end of the loop and so would not be incremented when
we skip to the next loop iteration. This would cause the loop to keep
seeing the same zero-length descriptor instead of moving on to the next
descriptor.

As the loop counter `i` still increments, the loop would eventually
terminate so there is no risk of being stuck here forever - but we
should still fix this to avoid wasting cycles.

To fix this, the RX descriptor index is incremented at the top of the
loop, in the for statement itself. The assignments of `entry` and `desc`
are brought into the loop to avoid the need for duplication.

Fixes: d8b48911fd24 ("ravb: fix ring memory allocation")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
---
Changes v2->v3:
  * Move comparison of `rx_packets` against `*quota` inside the loop.
Changes v1->v2:
  * Fix typos in commit message.
  * Add Sergey's Reviewed-by tag.

 drivers/net/ethernet/renesas/ravb_main.c | 25 ++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 7d231d011bff..3b870926af14 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -775,12 +775,15 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 	int limit;
 	int i;
 
-	entry = priv->cur_rx[q] % priv->num_rx_ring[q];
 	limit = priv->dirty_rx[q] + priv->num_rx_ring[q] - priv->cur_rx[q];
 	stats = &priv->stats[q];
 
-	desc = &priv->rx_ring[q].desc[entry];
-	for (i = 0; i < limit && rx_packets < *quota && desc->die_dt != DT_FEMPTY; i++) {
+	for (i = 0; i < limit; i++, priv->cur_rx[q]++) {
+		entry = priv->cur_rx[q] % priv->num_rx_ring[q];
+		desc = &priv->rx_ring[q].desc[entry];
+		if (rx_packets == *quota || desc->die_dt == DT_FEMPTY)
+			break;
+
 		/* Descriptor type must be checked before all other reads */
 		dma_rmb();
 		desc_status = desc->msc;
@@ -848,9 +851,6 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 				break;
 			}
 		}
-
-		entry = (++priv->cur_rx[q]) % priv->num_rx_ring[q];
-		desc = &priv->rx_ring[q].desc[entry];
 	}
 
 	/* Refill the RX ring buffers. */
@@ -891,7 +891,6 @@ static bool ravb_rx_rcar(struct net_device *ndev, int *quota, int q)
 {
 	struct ravb_private *priv = netdev_priv(ndev);
 	const struct ravb_hw_info *info = priv->info;
-	int entry = priv->cur_rx[q] % priv->num_rx_ring[q];
 	struct net_device_stats *stats = &priv->stats[q];
 	struct ravb_ex_rx_desc *desc;
 	unsigned int limit, i;
@@ -901,10 +900,15 @@ static bool ravb_rx_rcar(struct net_device *ndev, int *quota, int q)
 	int rx_packets = 0;
 	u8  desc_status;
 	u16 pkt_len;
+	int entry;
 
 	limit = priv->dirty_rx[q] + priv->num_rx_ring[q] - priv->cur_rx[q];
-	desc = &priv->rx_ring[q].ex_desc[entry];
-	for (i = 0; i < limit && rx_packets < *quota && desc->die_dt != DT_FEMPTY; i++) {
+	for (i = 0; i < limit; i++, priv->cur_rx[q]++) {
+		entry = priv->cur_rx[q] % priv->num_rx_ring[q];
+		desc = &priv->rx_ring[q].ex_desc[entry];
+		if (rx_packets == *quota || desc->die_dt == DT_FEMPTY)
+			break;
+
 		/* Descriptor type must be checked before all other reads */
 		dma_rmb();
 		desc_status = desc->msc;
@@ -958,9 +962,6 @@ static bool ravb_rx_rcar(struct net_device *ndev, int *quota, int q)
 			rx_packets++;
 			stats->rx_bytes += pkt_len;
 		}
-
-		entry = (++priv->cur_rx[q]) % priv->num_rx_ring[q];
-		desc = &priv->rx_ring[q].ex_desc[entry];
 	}
 
 	/* Refill the RX ring buffers. */
-- 
2.39.2

[net PATCH v3 3/4] net: ravb: Fix GbEth jumbo packet RX checksum handling

[Paul Barker]

Sending a 7kB ping packet to the RZ/G2L in v6.9-rc2 causes the following
backtrace:

	WARNING: CPU: 0 PID: 0 at include/linux/skbuff.h:3127 skb_trim+0x30/0x38
	Hardware name: Renesas SMARC EVK based on r9a07g044l2 (DT)
	pc : skb_trim+0x30/0x38
	lr : ravb_rx_csum_gbeth+0x40/0x90
	Call trace:
	 skb_trim+0x30/0x38
	 ravb_rx_gbeth+0x56c/0x5cc
	 ravb_poll+0xa0/0x204
	 __napi_poll+0x38/0x17c

This is caused by ravb_rx_gbeth() calling ravb_rx_csum_gbeth() with the
wrong skb for a packet which spans multiple descriptors. To fix this,
use the correct skb.

Fixes: c2da9408579d ("ravb: Add Rx checksum offload support for GbEth")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
---
No changes v2->v3:
Changes v1->v2:
  * Trimmed the call trace in accordance with the docs [1].
  * Add Sergey's Reviewed-by tag.

[1]: https://docs.kernel.org/process/submitting-patches.html#backtraces-in-commit-messages

 drivers/net/ethernet/renesas/ravb_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 3b870926af14..6969cdeeb67a 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -843,7 +843,7 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 				priv->rx_1st_skb->protocol =
 					eth_type_trans(priv->rx_1st_skb, ndev);
 				if (ndev->features & NETIF_F_RXCSUM)
-					ravb_rx_csum_gbeth(skb);
+					ravb_rx_csum_gbeth(priv->rx_1st_skb);
 				napi_gro_receive(&priv->napi[q],
 						 priv->rx_1st_skb);
 				rx_packets++;
-- 
2.39.2

[net PATCH v3 4/4] net: ravb: Fix RX byte accounting for jumbo packets

[Paul Barker]

The RX byte accounting for jumbo packets was changed to fix a potential
use-after-free bug. However, that fix used the wrong variable and so
only accounted for the number of bytes in the final descriptor, not the
number of bytes in the whole packet.

To fix this, we can simply update our stats with the correct number of
bytes before calling napi_gro_receive().

Also rename pkt_len to desc_len in ravb_rx_gbeth() to avoid any future
confusion. The variable name pkt_len is correct in ravb_rx_rcar() as
that function does not handle packets spanning multiple descriptors.

Fixes: 5a5a3e564de6 ("ravb: Fix potential use-after-free in ravb_rx_gbeth()")
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
---
No changes v2->v3
Changes v1->v2:
  * Added Sergey's Reviewed-by tag.

 drivers/net/ethernet/renesas/ravb_main.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 6969cdeeb67a..fcb756d77681 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -769,7 +769,7 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 	dma_addr_t dma_addr;
 	int rx_packets = 0;
 	u8  desc_status;
-	u16 pkt_len;
+	u16 desc_len;
 	u8  die_dt;
 	int entry;
 	int limit;
@@ -787,10 +787,10 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 		/* Descriptor type must be checked before all other reads */
 		dma_rmb();
 		desc_status = desc->msc;
-		pkt_len = le16_to_cpu(desc->ds_cc) & RX_DS;
+		desc_len = le16_to_cpu(desc->ds_cc) & RX_DS;
 
 		/* We use 0-byte descriptors to mark the DMA mapping errors */
-		if (!pkt_len)
+		if (!desc_len)
 			continue;
 
 		if (desc_status & MSC_MC)
@@ -811,25 +811,25 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 			switch (die_dt) {
 			case DT_FSINGLE:
 				skb = ravb_get_skb_gbeth(ndev, entry, desc);
-				skb_put(skb, pkt_len);
+				skb_put(skb, desc_len);
 				skb->protocol = eth_type_trans(skb, ndev);
 				if (ndev->features & NETIF_F_RXCSUM)
 					ravb_rx_csum_gbeth(skb);
 				napi_gro_receive(&priv->napi[q], skb);
 				rx_packets++;
-				stats->rx_bytes += pkt_len;
+				stats->rx_bytes += desc_len;
 				break;
 			case DT_FSTART:
 				priv->rx_1st_skb = ravb_get_skb_gbeth(ndev, entry, desc);
-				skb_put(priv->rx_1st_skb, pkt_len);
+				skb_put(priv->rx_1st_skb, desc_len);
 				break;
 			case DT_FMID:
 				skb = ravb_get_skb_gbeth(ndev, entry, desc);
 				skb_copy_to_linear_data_offset(priv->rx_1st_skb,
 							       priv->rx_1st_skb->len,
 							       skb->data,
-							       pkt_len);
-				skb_put(priv->rx_1st_skb, pkt_len);
+							       desc_len);
+				skb_put(priv->rx_1st_skb, desc_len);
 				dev_kfree_skb(skb);
 				break;
 			case DT_FEND:
@@ -837,17 +837,17 @@ static bool ravb_rx_gbeth(struct net_device *ndev, int *quota, int q)
 				skb_copy_to_linear_data_offset(priv->rx_1st_skb,
 							       priv->rx_1st_skb->len,
 							       skb->data,
-							       pkt_len);
-				skb_put(priv->rx_1st_skb, pkt_len);
+							       desc_len);
+				skb_put(priv->rx_1st_skb, desc_len);
 				dev_kfree_skb(skb);
 				priv->rx_1st_skb->protocol =
 					eth_type_trans(priv->rx_1st_skb, ndev);
 				if (ndev->features & NETIF_F_RXCSUM)
 					ravb_rx_csum_gbeth(priv->rx_1st_skb);
+				stats->rx_bytes += priv->rx_1st_skb->len;
 				napi_gro_receive(&priv->napi[q],
 						 priv->rx_1st_skb);
 				rx_packets++;
-				stats->rx_bytes += pkt_len;
 				break;
 			}
 		}
-- 
2.39.2

Re: [net PATCH v3 0/4] ravb Ethernet driver bugfixes

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (main)
by Paolo Abeni <pabeni@redhat.com>:

On Tue, 16 Apr 2024 13:02:50 +0100 you wrote:
> These patches fix bugs found during recent work on the ravb driver.
> 
> Patches 1 & 2 affect the R-Car code paths so have been tested on an
> R-Car M3N Salvator-XS board - this is the only R-Car board I currently
> have access to.
> 
> Patches 2, 3 & 4 affect the GbEth code paths so have been tested on
> RZ/G2L and RZ/G2UL SMARC EVK boards.
> 
> [...]

Here is the summary with links:
  - [net,v3,1/4] net: ravb: Count packets instead of descriptors in R-Car RX path
    https://git.kernel.org/netdev/net/c/def52db470df
  - [net,v3,2/4] net: ravb: Allow RX loop to move past DMA mapping errors
    https://git.kernel.org/netdev/net/c/a892493a3434
  - [net,v3,3/4] net: ravb: Fix GbEth jumbo packet RX checksum handling
    https://git.kernel.org/netdev/net/c/c7c449502b51
  - [net,v3,4/4] net: ravb: Fix RX byte accounting for jumbo packets
    https://git.kernel.org/netdev/net/c/2e36c9fbc476

You are awesome, thank you!
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