2022-03-09 16:14:24

by Jianglei Nie

Subject: [PATCH v2] net: arc_emac: Fix use after free in arc_mdio_probe()

If bus->state is equal to MDIOBUS_ALLOCATED, mdiobus_free(bus) will free
the "bus". But bus->name is still used in the next line, which will lead
to a use after free.

We can fix it by putting the name in a local variable and make the
bus->name point to the rodata section "name",then use the name in the
error message without referring to bus to avoid the uaf.

Signed-off-by: Jianglei Nie <[email protected]>
---
drivers/net/ethernet/arc/emac_mdio.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/arc/emac_mdio.c b/drivers/net/ethernet/arc/emac_mdio.c
index 9acf589b1178..87f40c2ba904 100644
--- a/drivers/net/ethernet/arc/emac_mdio.c
+++ b/drivers/net/ethernet/arc/emac_mdio.c
@@ -132,6 +132,7 @@ int arc_mdio_probe(struct arc_emac_priv *priv)
{
struct arc_emac_mdio_bus_data *data = &priv->bus_data;
struct device_node *np = priv->dev->of_node;
+ const char *name = "Synopsys MII Bus";
struct mii_bus *bus;
int error;

@@ -142,7 +143,7 @@ int arc_mdio_probe(struct arc_emac_priv *priv)
priv->bus = bus;
bus->priv = priv;
bus->parent = priv->dev;
- bus->name = "Synopsys MII Bus";
+ bus->name = name;
bus->read = &arc_mdio_read;
bus->write = &arc_mdio_write;
bus->reset = &arc_mdio_reset;
@@ -167,7 +168,7 @@ int arc_mdio_probe(struct arc_emac_priv *priv)
if (error) {
mdiobus_free(bus);
return dev_err_probe(priv->dev, error,
- "cannot register MDIO bus %s\n", bus->name);
+ "cannot register MDIO bus %s\n", name);
}

return 0;
--
2.25.1

2022-03-11 22:05:28

by patchwork-bot+netdevbpf

Subject: Re: [PATCH v2] net: arc_emac: Fix use after free in arc_mdio_probe()

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <[email protected]>:

On Wed, 9 Mar 2022 20:18:24 +0800 you wrote:
> If bus->state is equal to MDIOBUS_ALLOCATED, mdiobus_free(bus) will free
> the "bus". But bus->name is still used in the next line, which will lead
> to a use after free.
>
> We can fix it by putting the name in a local variable and make the
> bus->name point to the rodata section "name",then use the name in the
> error message without referring to bus to avoid the uaf.
>
> [...]

Here is the summary with links:
- [v2] net: arc_emac: Fix use after free in arc_mdio_probe()
https://git.kernel.org/netdev/net/c/bc0e610a6eb0

You are awesome, thank you!
--
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