Re: [PATCH net] net: stmmac: dwmac-rk: Ensure clk_phy doesn't contain invalid address

[Simon Horman <horms@kernel.org>]

On Thu, Sep 04, 2025 at 03:12:24AM +0000, Yao Zi wrote:
> We must set the clk_phy pointer to NULL to indicating it isn't available
> if the optional phy clock couldn't be obtained. Otherwise the error code
> returned by of_clk_get() could be wrongly taken as an address, causing
> invalid pointer dereference when later clk_phy is passed to
> clk_prepare_enable().
> 
> Fixes: da114122b831 ("net: ethernet: stmmac: dwmac-rk: Make the clk_phy could be used for external phy")
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> On next-20250903, the fixed commit causes NULL pointer dereference on
> Radxa E20C during probe of dwmac-rk, a typical dmesg looks like
> 
> [    0.273324] rk_gmac-dwmac ffbe0000.ethernet: IRQ eth_lpi not found
> [    0.273888] rk_gmac-dwmac ffbe0000.ethernet: IRQ sfty not found
> [    0.274520] rk_gmac-dwmac ffbe0000.ethernet: PTP uses main clock
> [    0.275226] rk_gmac-dwmac ffbe0000.ethernet: clock input or output? (output).
> [    0.275867] rk_gmac-dwmac ffbe0000.ethernet: Can not read property: tx_delay.
> [    0.276491] rk_gmac-dwmac ffbe0000.ethernet: set tx_delay to 0x30
> [    0.277026] rk_gmac-dwmac ffbe0000.ethernet: Can not read property: rx_delay.
> [    0.278086] rk_gmac-dwmac ffbe0000.ethernet: set rx_delay to 0x10
> [    0.278658] rk_gmac-dwmac ffbe0000.ethernet: integrated PHY? (no).
> [    0.279249] Unable to handle kernel paging request at virtual address fffffffffffffffe
> [    0.279948] Mem abort info:
> [    0.280195]   ESR = 0x000000096000006
> [    0.280523]   EC = 0x25: DABT (current EL), IL = 32 bits
> [    0.280989]   SET = 0, FnV = 0
> [    0.281287]   EA = 0, S1PTW = 0
> [    0.281574]   FSC = 0x06: level 2 translation fault
> 
> where the invalid address is just -ENOENT (-2).
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
> index cf619a428664..26ec8ae662a6 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
> @@ -1414,11 +1414,17 @@ static int rk_gmac_clk_init(struct plat_stmmacenet_data *plat)
>  	if (plat->phy_node) {
>  		bsp_priv->clk_phy = of_clk_get(plat->phy_node, 0);
>  		ret = PTR_ERR_OR_ZERO(bsp_priv->clk_phy);
> -		/* If it is not integrated_phy, clk_phy is optional */
> +		/*
> +		 * If it is not integrated_phy, clk_phy is optional. But we must
> +		 * set bsp_priv->clk_phy to NULL if clk_phy isn't proivded, or
> +		 * the error code could be wrongly taken as an invalid pointer.
> +		 */
>  		if (bsp_priv->integrated_phy) {
>  			if (ret)
>  				return dev_err_probe(dev, ret, "Cannot get PHY clock\n");
>  			clk_set_rate(bsp_priv->clk_phy, 50000000);
> +		} else if (ret) {
> +			bsp_priv->clk_phy = NULL;
>  		}
>  	}

Thanks, and sorry for my early confusion about applying this patch.

I agree that the bug you point out is addressed by this patch.
Although I wonder if it is cleaner not to set bsp_priv->clk_phy
unless there is no error, rather than setting it then resetting
it if there is an error.

More importantly, I wonder if there is another bug: does clk_set_rate need
to be called in the case where there is no error and bsp_priv->integrated_phy
is false?

So I am wondering if it makes sense to go with something like this.
(Compile tested only!)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
index 266c53379236..a25816af2c37 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
@@ -1411,12 +1411,16 @@ static int rk_gmac_clk_init(struct plat_stmmacenet_data *plat)
 	}
 
 	if (plat->phy_node) {
-		bsp_priv->clk_phy = of_clk_get(plat->phy_node, 0);
-		ret = PTR_ERR_OR_ZERO(bsp_priv->clk_phy);
-		/* If it is not integrated_phy, clk_phy is optional */
-		if (bsp_priv->integrated_phy) {
-			if (ret)
+		struct clk *clk_phy;
+
+		clk_phy = of_clk_get(plat->phy_node, 0);
+		ret = PTR_ERR_OR_ZERO(clk_phy);
+		if (ret) {
+			/* If it is not integrated_phy, clk_phy is optional */
+			if (bsp_priv->integrated_phy)
 				return dev_err_probe(dev, ret, "Cannot get PHY clock\n");
+		} else {
+			bsp_priv->clk_phy = clk_phy;
 			clk_set_rate(bsp_priv->clk_phy, 50000000);
 		}
 	}

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make sure you wait 24h before the original post.

See: https://docs.kernel.org/process/maintainer-netdev.html