[PATCH] net: sparx5: Fix return type of sparx5_port_xmit_impl

[PATCH] net: sparx5: Fix return type of sparx5_port_xmit_impl

[Nathan Huckleberry]

The ndo_start_xmit field in net_device_ops is expected to be of type
netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).

The mismatched return type breaks forward edge kCFI since the underlying
function definition does not match the function hook definition.

The return type of sparx5_port_xmit_impl should be changed from int to
netdev_tx_t.

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1703
Cc: llvm@lists.linux.dev
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
---
 drivers/net/ethernet/microchip/sparx5/sparx5_packet.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
index 21844beba72d..83c16ca5b30f 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
@@ -222,13 +222,13 @@ static int sparx5_inject(struct sparx5 *sparx5,
 	return NETDEV_TX_OK;
 }
 
-int sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
+netdev_tx_t sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
 {
 	struct net_device_stats *stats = &dev->stats;
 	struct sparx5_port *port = netdev_priv(dev);
 	struct sparx5 *sparx5 = port->sparx5;
 	u32 ifh[IFH_LEN];
-	int ret;
+	netdev_tx_t ret;
 
 	memset(ifh, 0, IFH_LEN * 4);
 	sparx5_set_port_ifh(ifh, port->portno);
-- 
2.37.2.789.g6183377224-goog


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Re: [PATCH] net: sparx5: Fix return type of sparx5_port_xmit_impl

[Casper Andersson]

Hi,

On 2022-09-12 14:44, Nathan Huckleberry wrote:
> The ndo_start_xmit field in net_device_ops is expected to be of type
> netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).
> 
> The mismatched return type breaks forward edge kCFI since the underlying
> function definition does not match the function hook definition.
> 
> The return type of sparx5_port_xmit_impl should be changed from int to
> netdev_tx_t.

I noticed that the functions that assign the return value inside
sparx5_port_xmit_impl also have return type int, which would ideally
also be changed. But a bigger issue might be that
sparx5_ptp_txtstamp_request and sparx5_inject (called inside
sparx5_port_xmit_impl) returns -EBUSY (-16), when they should return
NETDEV_TX_BUSY (16). If this is an issue then it also needs to be fixed.

sparx5_fdma_xmit also has int return type, but always returns
NETDEV_TX_OK right now.

Best Regards,
Casper


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Re: [PATCH] net: sparx5: Fix return type of sparx5_port_xmit_impl

[Nathan Huckleberry]

Hey Casper,

On Tue, Sep 13, 2022 at 1:15 AM Casper Andersson <casper.casan@gmail.com> wrote:
>
> Hi,
>
> On 2022-09-12 14:44, Nathan Huckleberry wrote:
> > The ndo_start_xmit field in net_device_ops is expected to be of type
> > netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).
> >
> > The mismatched return type breaks forward edge kCFI since the underlying
> > function definition does not match the function hook definition.
> >
> > The return type of sparx5_port_xmit_impl should be changed from int to
> > netdev_tx_t.
>
> I noticed that the functions that assign the return value inside
> sparx5_port_xmit_impl also have return type int, which would ideally
> also be changed. But a bigger issue might be that
> sparx5_ptp_txtstamp_request and sparx5_inject (called inside
> sparx5_port_xmit_impl) returns -EBUSY (-16), when they should return
> NETDEV_TX_BUSY (16). If this is an issue then it also needs to be fixed.

It's not clear to me what happens when returning an error vs
NETDEV_TX_BUSY. The netdev_tx_t enum allows negative values, so
returning an error might be valid. If anyone more familiar with this
code has insight into why it's done like this, that'd be useful.

The important bit here for me is changing the return type on the
hooked function since the current code will cause panics.

>
> sparx5_fdma_xmit also has int return type, but always returns
> NETDEV_TX_OK right now.
>
> Best Regards,
> Casper
>

Thanks,
Huck

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Re: [PATCH] net: sparx5: Fix return type of sparx5_port_xmit_impl

[Jakub Kicinski]

On Tue, 13 Sep 2022 10:15:48 +0200 Casper Andersson wrote:
> I noticed that the functions that assign the return value inside
> sparx5_port_xmit_impl also have return type int, which would ideally
> also be changed. But a bigger issue might be that
> sparx5_ptp_txtstamp_request and sparx5_inject (called inside
> sparx5_port_xmit_impl) returns -EBUSY (-16),

Yes, that seems off. IIUC error codes are treated as drops, 
but the driver doesn't free the frame. So it's likely a leak.

> when they should return NETDEV_TX_BUSY (16). If this is an issue then
> it also needs to be fixed.

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Re: [PATCH] net: sparx5: Fix return type of sparx5_port_xmit_impl

[Jakub Kicinski]

On Mon, 12 Sep 2022 14:44:29 -0700 Nathan Huckleberry wrote:
> -int sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
> +netdev_tx_t sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)

Similarly to mana this has a prototype.

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[PATCH v2] net: sparx5: Fix return type of sparx5_port_xmit_impl

[Nathan Huckleberry]

The ndo_start_xmit field in net_device_ops is expected to be of type
netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).

The mismatched return type breaks forward edge kCFI since the underlying
function definition does not match the function hook definition.

The return type of sparx5_port_xmit_impl should be changed from int to
netdev_tx_t.

Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://github.com/ClangBuiltLinux/linux/issues/1703
Cc: llvm@lists.linux.dev
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
---

Changes v1 -> v2
- Updated header file

 drivers/net/ethernet/microchip/sparx5/sparx5_main.h   | 2 +-
 drivers/net/ethernet/microchip/sparx5/sparx5_packet.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_main.h b/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
index 8b42cad0e49c..7a83222caa73 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_main.h
@@ -305,7 +305,7 @@ struct frame_info {
 void sparx5_xtr_flush(struct sparx5 *sparx5, u8 grp);
 void sparx5_ifh_parse(u32 *ifh, struct frame_info *info);
 irqreturn_t sparx5_xtr_handler(int irq, void *_priv);
-int sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev);
+netdev_tx_t sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev);
 int sparx5_manual_injection_mode(struct sparx5 *sparx5);
 void sparx5_port_inj_timer_setup(struct sparx5_port *port);
 
diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
index 21844beba72d..83c16ca5b30f 100644
--- a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
+++ b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
@@ -222,13 +222,13 @@ static int sparx5_inject(struct sparx5 *sparx5,
 	return NETDEV_TX_OK;
 }
 
-int sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
+netdev_tx_t sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
 {
 	struct net_device_stats *stats = &dev->stats;
 	struct sparx5_port *port = netdev_priv(dev);
 	struct sparx5 *sparx5 = port->sparx5;
 	u32 ifh[IFH_LEN];
-	int ret;
+	netdev_tx_t ret;
 
 	memset(ifh, 0, IFH_LEN * 4);
 	sparx5_set_port_ifh(ifh, port->portno);
-- 
2.38.0.rc1.362.ged0d419d3c-goog


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Re: [PATCH v2] net: sparx5: Fix return type of sparx5_port_xmit_impl

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Thu, 29 Sep 2022 11:19:47 -0700 you wrote:
> The ndo_start_xmit field in net_device_ops is expected to be of type
> netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb, struct net_device *dev).
> 
> The mismatched return type breaks forward edge kCFI since the underlying
> function definition does not match the function hook definition.
> 
> The return type of sparx5_port_xmit_impl should be changed from int to
> netdev_tx_t.
> 
> [...]

Here is the summary with links:
  - [v2] net: sparx5: Fix return type of sparx5_port_xmit_impl
    https://git.kernel.org/netdev/net/c/73ea73507359

You are awesome, thank you!
-- 
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