drivers/net/ethernet/arc/emac_mdio.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
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 bus->name in a local variable and then use
the name in the error message without referring to bus to avoid the uaf.
Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
---
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..33fd63d227ef 100644
--- a/drivers/net/ethernet/arc/emac_mdio.c
+++ b/drivers/net/ethernet/arc/emac_mdio.c
@@ -134,6 +134,7 @@ int arc_mdio_probe(struct arc_emac_priv *priv)
struct device_node *np = priv->dev->of_node;
struct mii_bus *bus;
int error;
+ const char *name = "Synopsys MII Bus";
bus = mdiobus_alloc();
if (!bus)
@@ -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;
--
2.25.1On Tue, Mar 08, 2022 at 07:10:05PM +0800, Jianglei Nie 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 bus->name in a local variable and then use
> the name in the error message without referring to bus to avoid the uaf.
>
> Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
> ---
> 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..33fd63d227ef 100644
> --- a/drivers/net/ethernet/arc/emac_mdio.c
> +++ b/drivers/net/ethernet/arc/emac_mdio.c
> @@ -134,6 +134,7 @@ int arc_mdio_probe(struct arc_emac_priv *priv)
> struct device_node *np = priv->dev->of_node;
> struct mii_bus *bus;
> int error;
> + const char *name = "Synopsys MII Bus";
Netdev uses reverse christmass tree, meaning you need to sort
variables longest to shortest.
I'm also wondering about the lifetime of name. name itself is a stack
variable, so it will disappear as soon as the function exits. The
string itself is in the rodata section. But is a copy made onto the
stack, or does bus->name point to the rodata?
Andrew
> bus = mdiobus_alloc();
> if (!bus)
> @@ -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
>
Hello,
> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: 2022年3月8日 21:43
> To: Jianglei Nie
> Cc: davem@davemloft.net; kuba@kernel.org; Cai,Huoqing;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH] net: arc_emac: Fix use after free in arc_mdio_probe()
If resend a patch, you can use prefix "[PATCH v2]" in subject.
e.g. git format-patch -1 -v2
>
> On Tue, Mar 08, 2022 at 07:10:05PM +0800, Jianglei Nie 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 bus->name in a local variable and then use
> > the name in the error message without referring to bus to avoid the uaf.
> >
> > Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
> > ---
> > 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..33fd63d227ef 100644
> > --- a/drivers/net/ethernet/arc/emac_mdio.c
> > +++ b/drivers/net/ethernet/arc/emac_mdio.c
> > @@ -134,6 +134,7 @@ int arc_mdio_probe(struct arc_emac_priv *priv)
> > struct device_node *np = priv->dev->of_node;
> > struct mii_bus *bus;
> > int error;
> > + const char *name = "Synopsys MII Bus";
>
> Netdev uses reverse christmass tree, meaning you need to sort
> variables longest to shortest.
>
> I'm also wondering about the lifetime of name. name itself is a stack
> variable, so it will disappear as soon as the function exits. The
> string itself is in the rodata section. But is a copy made onto the
> stack, or does bus->name point to the rodata?
>
> Andrew
>
> > bus = mdiobus_alloc();
> > if (!bus)
> > @@ -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
> >
> If resend a patch, you can use prefix "[PATCH v2]" in subject. > e.g. git format-patch -1 -v2 Yes. But please also read the netdev FAQ: https://docs.kernel.org/networking/netdev-FAQ.html Andrew
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