Syzbot reported memory leak in MDIO bus interface, the problem was in
wrong state logic.
MDIOBUS_ALLOCATED indicates 2 states:
1. Bus is only allocated
2. Bus allocated and __mdiobus_register() fails, but
device_register() was called
In case of device_register() has been called we should call put_device()
to correctly free the memory allocated for this device, but mdiobus_free()
was just calling kfree(dev) in case of MDIOBUS_ALLOCATED state
To avoid this behaviour we can add new intermediate state, which means,
that we have called device_regiter(), but failed on any of the next steps.
Clean up process for this state is the same as for MDIOBUS_UNREGISTERED,
but MDIOBUS_UNREGISTERED name does not fit to the logic described above.
Fixes: 46abc02175b3 ("phylib: give mdio buses a device tree presence")
Reported-and-tested-by: [email protected]
Signed-off-by: Pavel Skripkin <[email protected]>
---
drivers/net/phy/mdio_bus.c | 4 +++-
include/linux/phy.h | 1 +
2 files changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 53f034fc2ef7..ed764638b449 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -540,6 +540,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
return -EINVAL;
}
+ bus->state = MDIOBUS_DEV_REGISTERED;
+
mutex_init(&bus->mdio_lock);
mutex_init(&bus->shared_lock);
@@ -647,7 +649,7 @@ void mdiobus_free(struct mii_bus *bus)
return;
}
- BUG_ON(bus->state != MDIOBUS_UNREGISTERED);
+ BUG_ON(bus->state != MDIOBUS_UNREGISTERED && bus->state != MDIOBUS_DEV_REGISTERED);
bus->state = MDIOBUS_RELEASED;
put_device(&bus->dev);
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 736e1d1a47c4..41d2ccdacd5e 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -343,6 +343,7 @@ struct mii_bus {
MDIOBUS_REGISTERED,
MDIOBUS_UNREGISTERED,
MDIOBUS_RELEASED,
+ MDIOBUS_DEV_REGISTERED,
} state;
/** @dev: Kernel device representation */
--
2.33.0
On 9/27/21 14:20, Pavel Skripkin wrote:
> Syzbot reported memory leak in MDIO bus interface, the problem was in
> wrong state logic.
>
> MDIOBUS_ALLOCATED indicates 2 states:
> 1. Bus is only allocated
> 2. Bus allocated and __mdiobus_register() fails, but
> device_register() was called
>
> In case of device_register() has been called we should call put_device()
> to correctly free the memory allocated for this device, but mdiobus_free()
> was just calling kfree(dev) in case of MDIOBUS_ALLOCATED state
>
> To avoid this behaviour we can add new intermediate state, which means,
> that we have called device_regiter(), but failed on any of the next steps.
> Clean up process for this state is the same as for MDIOBUS_UNREGISTERED,
> but MDIOBUS_UNREGISTERED name does not fit to the logic described above.
>
> Fixes: 46abc02175b3 ("phylib: give mdio buses a device tree presence")
> Reported-and-tested-by: [email protected]
> Signed-off-by: Pavel Skripkin <[email protected]>
I've just found, that this syzkaller bug has been closed by Yanfei's
patch [1], but Yanfei's Reported-by: is wrong, IMO.
Yanfei's patch fixed other memory leak and it's not related to bug
reported by syzkaller. If you take a look at log [2] you won't find
error message about mii_bus registration failure, i.e the error happened
a bit latter (more precisely in mdiobus_scan()).
Since, Yanfei's patch is already applied, we cannot remove this tag, so
I am informing you about this situation to break possible confusions
about 2 different patches with same Reported-by: tag :)
Thanks
[1]
https://lore.kernel.org/netdev/[email protected]/
[2] https://syzkaller.appspot.com/text?tag=CrashLog&x=131c754b300000
With regards,
Pavel Skripkin
This reverts commit ab609f25d19858513919369ff3d9a63c02cd9e2e.
This patch is correct in the sense that we _should_ call device_put() in
case of device_register() failure, but the problem in this code is more
vast.
We need to set bus->state to UNMDIOBUS_REGISTERED before calling
device_register() to correctly release the device in mdiobus_free().
This patch prevents us from doing it, since in case of device_register()
failure put_device() will be called 2 times and it will cause UAF or
something else.
Also, Reported-by: tag in revered commit was wrong, since syzbot
reported different leak in same function.
Link: https://lore.kernel.org/netdev/20210928092657.GI2048@kadam/
Cc: Yanfei Xu <[email protected]>
Signed-off-by: Pavel Skripkin <[email protected]>
---
Changes in v2:
Added this revert
---
drivers/net/phy/mdio_bus.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 6f4b4e5df639..53f034fc2ef7 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -537,7 +537,6 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
err = device_register(&bus->dev);
if (err) {
pr_err("mii_bus %s failed to register\n", bus->id);
- put_device(&bus->dev);
return -EINVAL;
}
--
2.33.0
Syzbot reported memory leak in MDIO bus interface, the problem was in
wrong state logic.
MDIOBUS_ALLOCATED indicates 2 states:
1. Bus is only allocated
2. Bus allocated and __mdiobus_register() fails, but
device_register() was called
In case of device_register() has been called we should call put_device()
to correctly free the memory allocated for this device, but mdiobus_free()
calls just kfree(dev) in case of MDIOBUS_ALLOCATED state
To avoid this behaviour we need to set bus->state to MDIOBUS_UNREGISTERED
_before_ calling device_register(), because put_device() should be
called even in case of device_register() failure.
Link: https://lore.kernel.org/netdev/[email protected]/
Fixes: 46abc02175b3 ("phylib: give mdio buses a device tree presence")
Reported-and-tested-by: [email protected]
Signed-off-by: Pavel Skripkin <[email protected]>
---
Changes in v2:
Removed new state, since MDIOBUS_UNREGISTERED can be used. Also, moved
bus->state initialization _before_ device_register() call, because
Yanfei's patch is reverted in [v2 1/2]
---
drivers/net/phy/mdio_bus.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 53f034fc2ef7..2d16a93af1ae 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -534,6 +534,13 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner)
bus->dev.groups = NULL;
dev_set_name(&bus->dev, "%s", bus->id);
+ /* We need to set state to MDIOBUS_UNREGISTERED to correctly realese
+ * the device in mdiobus_free()
+ *
+ * State will be updated later in this function in case of success
+ */
+ bus->state == MDIOBUS_UNREGISTERED;
+
err = device_register(&bus->dev);
if (err) {
pr_err("mii_bus %s failed to register\n", bus->id);
--
2.33.0
On Tue, Sep 28, 2021 at 11:40:15PM +0300, Pavel Skripkin wrote:
> Syzbot reported memory leak in MDIO bus interface, the problem was in
> wrong state logic.
>
> MDIOBUS_ALLOCATED indicates 2 states:
> 1. Bus is only allocated
> 2. Bus allocated and __mdiobus_register() fails, but
> device_register() was called
>
> In case of device_register() has been called we should call put_device()
> to correctly free the memory allocated for this device, but mdiobus_free()
> calls just kfree(dev) in case of MDIOBUS_ALLOCATED state
>
> To avoid this behaviour we need to set bus->state to MDIOBUS_UNREGISTERED
> _before_ calling device_register(), because put_device() should be
> called even in case of device_register() failure.
>
> Link: https://lore.kernel.org/netdev/[email protected]/
> Fixes: 46abc02175b3 ("phylib: give mdio buses a device tree presence")
> Reported-and-tested-by: [email protected]
> Signed-off-by: Pavel Skripkin <[email protected]>
Thanks!
Reviewed-by: Dan Carpenter <[email protected]>
regards,
dan carpenter
On 9/29/21 4:39 AM, Pavel Skripkin wrote:
> This reverts commit ab609f25d19858513919369ff3d9a63c02cd9e2e.
>
> This patch is correct in the sense that we_should_ call device_put() in
> case of device_register() failure, but the problem in this code is more
> vast.
>
> We need to set bus->state to UNMDIOBUS_REGISTERED before calling
> device_register() to correctly release the device in mdiobus_free().
> This patch prevents us from doing it, since in case of device_register()
> failure put_device() will be called 2 times and it will cause UAF or
> something else.
>
> Also, Reported-by: tag in revered commit was wrong, since syzbot
> reported different leak in same function.
>
> Link:https://lore.kernel.org/netdev/20210928092657.GI2048@kadam/
> Cc: Yanfei Xu<[email protected]>
> Signed-off-by: Pavel Skripkin<[email protected]>
> ---
>
> Changes in v2:
> Added this revert
Acked-by: Yanfei Xu<[email protected]>
Thanks,
Yanfei
On Tue, 28 Sep 2021 23:40:15 +0300 Pavel Skripkin wrote:
> + /* We need to set state to MDIOBUS_UNREGISTERED to correctly realese
> + * the device in mdiobus_free()
> + *
> + * State will be updated later in this function in case of success
> + */
> + bus->state == MDIOBUS_UNREGISTERED;
IDK how syzbot has tested it but clearly we should blindly
depend on that.
s/==/=/
Compiler would have told you this.
On 9/30/21 02:48, Jakub Kicinski wrote:
> On Tue, 28 Sep 2021 23:40:15 +0300 Pavel Skripkin wrote:
>> + /* We need to set state to MDIOBUS_UNREGISTERED to correctly realese
>> + * the device in mdiobus_free()
>> + *
>> + * State will be updated later in this function in case of success
>> + */
>> + bus->state == MDIOBUS_UNREGISTERED;
>
> IDK how syzbot has tested it but clearly we should blindly
> depend on that.
>
> s/==/=/
>
> Compiler would have told you this.
>
whooops... sorry about that. syzbot has tested v1. v2 is same, but
without new state (so, the logic in v1 and v2 is the same).
I guess, it's copy-paste error on my side :). Will send v3 this evening
With regards,
Pavel Skripkin