Subject: Re: [PATCH v2 1/1] drivers: net: cpsw: Prevent NUll pointer dereference with two PHYs

From: Grygorii Strashko <[email-masked]>
Date: Tue, 19 Apr 2016 17:41:07 +0300

Hi,

On 04/19/2016 04:56 PM, Andrew Goodbody wrote:
> Adding a 2nd PHY to cpsw results in a NULL pointer dereference
> as below. Fix by maintaining a reference to each PHY node in slave
> struct instead of a single reference in the priv struct which was
> overwritten by the 2nd PHY.

David, Is it possible to drop prev version of this patch from linux-next
- it breaks boot on many TI boards with -next.

> 
> [   17.870933] Unable to handle kernel NULL pointer dereference at virtual address 00000180
> [   17.879557] pgd = dc8bc000
> [   17.882514] [00000180] *pgd=9c882831, *pte=00000000, *ppte=00000000
> [   17.889213] Internal error: Oops: 17 [#1] ARM
> [   17.893838] Modules linked in:
> [   17.897102] CPU: 0 PID: 1657 Comm: connmand Not tainted 4.5.0-ge463dfb-dirty #11
> [   17.904947] Hardware name: Cambrionix whippet
> [   17.909576] task: dc859240 ti: dc968000 task.ti: dc968000
> [   17.915339] PC is at phy_attached_print+0x18/0x8c
> [   17.920339] LR is at phy_attached_info+0x14/0x18
> [   17.925247] pc : [<c042baec>]    lr : [<c042bb74>]    psr: 600f0113
> [   17.925247] sp : dc969cf8  ip : dc969d28  fp : dc969d18
> [   17.937425] r10: dda7a400  r9 : 00000000  r8 : 00000000
> [   17.942971] r7 : 00000001  r6 : ddb00480  r5 : ddb8cb34  r4 : 00000000
> [   17.949898] r3 : c0954cc0  r2 : c09562b0  r1 : 00000000  r0 : 00000000
> [   17.956829] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> [   17.964401] Control: 10c5387d  Table: 9c8bc019  DAC: 00000051
> [   17.970500] Process connmand (pid: 1657, stack limit = 0xdc968210)
> [   17.977059] Stack: (0xdc969cf8 to 0xdc96a000)

[...]

> [   18.323956] [<c05e4cb8>] (inet_ioctl) from [<c055f5ac>] (sock_ioctl+0x15c/0x2d8)
> [   18.331829] [<c055f450>] (sock_ioctl) from [<c010b388>] (do_vfs_ioctl+0x98/0x8d0)
> [   18.339765]  r7:00008914 r6:dc8ab4c0 r5:dd257ae0 r4:beaeda20
> [   18.345822] [<c010b2f0>] (do_vfs_ioctl) from [<c010bc34>] (SyS_ioctl+0x74/0x84)
> [   18.353573]  r10:00000000 r9:00000011 r8:beaeda20 r7:00008914 r6:dc8ab4c0 r5:dc8ab4c0
> [   18.361924]  r4:00000000
> [   18.364653] [<c010bbc0>] (SyS_ioctl) from [<c00163e0>] (ret_fast_syscall+0x0/0x3c)
> [   18.372682]  r9:dc968000 r8:c00165e8 r7:00000036 r6:00000002 r5:00000011 r4:00000000
> [   18.380960] Code: e92dd810 e24cb010 e24dd010 e59b4004 (e5902180)
> [   18.387580] ---[ end trace c80529466223f3f3 ]---

^ Could you make it shorter and drop timestamps, pls?

> 
> Signed-off-by: Andrew Goodbody <[email-masked]>
> ---
> 
> v2 - Move allocation of memory for priv->slaves to inside cpsw_probe_dt so it
>       has data->slaves initialised first which is needed to calculate size
> 
>   drivers/net/ethernet/ti/cpsw.c | 30 +++++++++++++++---------------
>   1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/cpsw.c b/drivers/net/ethernet/ti/cpsw.c
> index 42fdfd4..e62909c 100644
> --- a/drivers/net/ethernet/ti/cpsw.c
> +++ b/drivers/net/ethernet/ti/cpsw.c
> @@ -349,6 +349,7 @@ struct cpsw_slave {
>   	struct cpsw_slave_data		*data;
>   	struct phy_device		*phy;
>   	struct net_device		*ndev;
> +	struct device_node		*phy_node;
>   	u32				port_vlan;
>   	u32				open_stat;
>   };
> @@ -367,7 +368,6 @@ struct cpsw_priv {
>   	spinlock_t			lock;
>   	struct platform_device		*pdev;
>   	struct net_device		*ndev;
> -	struct device_node		*phy_node;
>   	struct napi_struct		napi_rx;
>   	struct napi_struct		napi_tx;
>   	struct device			*dev;
> @@ -1148,8 +1148,8 @@ static void cpsw_slave_open(struct cpsw_slave *slave, struct cpsw_priv *priv)
>   		cpsw_ale_add_mcast(priv->ale, priv->ndev->broadcast,
>   				   1 << slave_port, 0, 0, ALE_MCAST_FWD_2);
>   
> -	if (priv->phy_node)
> -		slave->phy = of_phy_connect(priv->ndev, priv->phy_node,
> +	if (slave->phy_node)
> +		slave->phy = of_phy_connect(priv->ndev, slave->phy_node,
>   				 &cpsw_adjust_link, 0, slave->data->phy_if);
>   	else
>   		slave->phy = phy_connect(priv->ndev, slave->data->phy_id,
> @@ -1946,7 +1946,7 @@ static int cpsw_probe_dt(struct cpsw_priv *priv,
>   	struct device_node *node = pdev->dev.of_node;
>   	struct device_node *slave_node;
>   	struct cpsw_platform_data *data = &priv->data;
> -	int i = 0, ret;
> +	int i, ret;
>   	u32 prop;
>   
>   	if (!node)
> @@ -1958,6 +1958,14 @@ static int cpsw_probe_dt(struct cpsw_priv *priv,
>   	}
>   	data->slaves = prop;
>   
> +	priv->slaves = devm_kzalloc(&pdev->dev,
> +				    sizeof(struct cpsw_slave) * data->slaves,
> +				    GFP_KERNEL);
> +	if (!priv->slaves)
> +		return -ENOMEM;
> +	for (i = 0; i < data->slaves; i++)
> +		priv->slaves[i].slave_num = i;
> +
>   	if (of_property_read_u32(node, "active_slave", &prop)) {
>   		dev_err(&pdev->dev, "Missing active_slave property in the DT.\n");
>   		return -EINVAL;
> @@ -2023,6 +2031,7 @@ static int cpsw_probe_dt(struct cpsw_priv *priv,
>   	if (ret)
>   		dev_warn(&pdev->dev, "Doesn't have any child node\n");
>   
> +	i = 0;
>   	for_each_child_of_node(node, slave_node) {
>   		struct cpsw_slave_data *slave_data = data->slave_data + i;
>   		const void *mac_addr = NULL;
> @@ -2033,7 +2042,8 @@ static int cpsw_probe_dt(struct cpsw_priv *priv,
>   		if (strcmp(slave_node->name, "slave"))
>   			continue;
>   
> -		priv->phy_node = of_parse_phandle(slave_node, "phy-handle", 0);
> +		priv->slaves[i].phy_node =
> +			of_parse_phandle(slave_node, "phy-handle", 0);

i++?

Ideally, the simplest way is to save phy_node in slave_data, but ...
(see comment below).

>   		parp = of_get_property(slave_node, "phy_id", &lenp);
>   		if (of_phy_is_fixed_link(slave_node)) {
>   			struct device_node *phy_node;
> @@ -2292,16 +2302,6 @@ static int cpsw_probe(struct platform_device *pdev)
>   
>   	memcpy(ndev->dev_addr, priv->mac_addr, ETH_ALEN);
>   
> -	priv->slaves = devm_kzalloc(&pdev->dev,
> -				    sizeof(struct cpsw_slave) * data->slaves,
> -				    GFP_KERNEL);
> -	if (!priv->slaves) {
> -		ret = -ENOMEM;
> -		goto clean_runtime_disable_ret;
> -	}
I don't think you can move this out from here - it will break legacy boot :(

> -	for (i = 0; i < data->slaves; i++)
> -		priv->slaves[i].slave_num = i;

Personally, I see only one safe way to do it without big rework -
do second pass of DT parsing here to fill phy_node field.

> -
>   	priv->slaves[0].ndev = ndev;
>   	priv->emac_port = 0;
>   
> 

-- 
regards,
-grygorii