Messages in this thread | | | Date | Fri, 03 Apr 2020 18:09:11 +0000 | From | René van Dorst <> | Subject | Re: [PATCH] net: dsa: mt7530: fix null pointer dereferencing in port5 setup |
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Quoting Chuanhong Guo <gch981213@gmail.com>:
Hi Chuanhong,
> The 2nd gmac of mediatek soc ethernet may not be connected to a PHY > and a phy-handle isn't always available. > Unfortunately, mt7530 dsa driver assumes that the 2nd gmac is always > connected to switch port 5 and setup mt7530 according to phy address > of 2nd gmac node, causing null pointer dereferencing when phy-handle > isn't defined in dts.
MT7530 tries to detect if 2nd GMAC is using a phy with phy-address 0 or 4. If so, switch port 5 needs to be setup so that PHY 0 or 4 is available via port 5 of the switch. Any MAC can talk to PHY 0/4 directly via port 5. This is also explained in the kernel docs mt7530.txt.
May be there are better way to detect that any node is using phy 0/4 of the switch.
Funny that I never tested this case that 2nd gmac node exits and is disabled without using port 5.
Thanks for the fix.
Tested-by: René van Dorst <opensource@vdorst.com>
Greats,
René
> This commit fix this setup code by checking return value of > of_parse_phandle before using it. > > Fixes: 38f790a80560 ("net: dsa: mt7530: Add support for port 5") > Signed-off-by: Chuanhong Guo <gch981213@gmail.com> > Cc: stable@vger.kernel.org > --- > > mt7530 is available as a standalone chip and we should not make it > tightly coupled with a specific type of ethernet dt binding in the > first place. > A proper fix is to replace this port detection logic with a dt > property under mt7530 node, but that's too much for linux-stable. > > drivers/net/dsa/mt7530.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c > index 6e91fe2f4b9a..1d53a4ebcd5a 100644 > --- a/drivers/net/dsa/mt7530.c > +++ b/drivers/net/dsa/mt7530.c > @@ -1414,6 +1414,9 @@ mt7530_setup(struct dsa_switch *ds) > continue; > > phy_node = of_parse_phandle(mac_np, "phy-handle", 0); > + if (!phy_node) > + continue; > + > if (phy_node->parent == priv->dev->of_node->parent) { > ret = of_get_phy_mode(mac_np, &interface); > if (ret && ret != -ENODEV) > -- > 2.25.1
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