[PATCH] mcb: fix error handling in mcb_alloc_bus()

[PATCH] mcb: fix error handling in mcb_alloc_bus()

[Dan Carpenter]

There are two bugs:
1) If ida_simple_get() fails then this code calls put_device(carrier)
   but we haven't yet called get_device(carrier) and probably that
   leads to a use after free.
2) After device_initialize() then we need to use put_device() to
   release the bus.  This will free the internal resources tied to the
   device and call mcb_free_bus() which will free the rest.

Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 drivers/mcb/mcb-core.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/mcb/mcb-core.c b/drivers/mcb/mcb-core.c
index 38fbb3b59873..38cc8340e817 100644
--- a/drivers/mcb/mcb-core.c
+++ b/drivers/mcb/mcb-core.c
@@ -277,8 +277,8 @@ struct mcb_bus *mcb_alloc_bus(struct device *carrier)
 
 	bus_nr = ida_simple_get(&mcb_ida, 0, 0, GFP_KERNEL);
 	if (bus_nr < 0) {
-		rc = bus_nr;
-		goto err_free;
+		kfree(bus);
+		return ERR_PTR(bus_nr);
 	}
 
 	bus->bus_nr = bus_nr;
@@ -293,12 +293,12 @@ struct mcb_bus *mcb_alloc_bus(struct device *carrier)
 	dev_set_name(&bus->dev, "mcb:%d", bus_nr);
 	rc = device_add(&bus->dev);
 	if (rc)
-		goto err_free;
+		goto err_put;
 
 	return bus;
-err_free:
-	put_device(carrier);
-	kfree(bus);
+
+err_put:
+	put_device(&bus->dev);
 	return ERR_PTR(rc);
 }
 EXPORT_SYMBOL_NS_GPL(mcb_alloc_bus, MCB);
-- 
2.30.2

Re: [PATCH] mcb: fix error handling in mcb_alloc_bus()

[Johannes Thumshirn]

Am 01.06.21 um 11:18 schrieb Dan Carpenter:
> There are two bugs:
> 1) If ida_simple_get() fails then this code calls put_device(carrier)
>    but we haven't yet called get_device(carrier) and probably that
>    leads to a use after free.
> 2) After device_initialize() then we need to use put_device() to
>    release the bus.  This will free the internal resources tied to the
>    device and call mcb_free_bus() which will free the rest.
>
> Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
> Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>

Thanks applied

Re: [PATCH] mcb: fix error handling in mcb_alloc_bus()

[Dan Carpenter]

On Tue, Jun 01, 2021 at 03:23:55PM +0200, Johannes Thumshirn wrote:
> 
> 
> Am 01.06.21 um 11:18 schrieb Dan Carpenter:
> > There are two bugs:
> > 1) If ida_simple_get() fails then this code calls put_device(carrier)
> >    but we haven't yet called get_device(carrier) and probably that
> >    leads to a use after free.
> > 2) After device_initialize() then we need to use put_device() to
> >    release the bus.  This will free the internal resources tied to the
> >    device and call mcb_free_bus() which will free the rest.
> >
> > Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
> > Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> 
> Thanks applied

I don't think this was actually applied and that's a good thing because
my patch wasn't correct.  It needs to call device_put() on both
carrier and &bus->dev.

I'm going to send a v2 fix for this.

regards,
dan carpenter

Re: [PATCH] mcb: fix error handling in mcb_alloc_bus()

[Dan Carpenter]

On Fri, Aug 06, 2021 at 04:32:40PM +0300, Dan Carpenter wrote:
> On Tue, Jun 01, 2021 at 03:23:55PM +0200, Johannes Thumshirn wrote:
> > 
> > 
> > Am 01.06.21 um 11:18 schrieb Dan Carpenter:
> > > There are two bugs:
> > > 1) If ida_simple_get() fails then this code calls put_device(carrier)
> > >    but we haven't yet called get_device(carrier) and probably that
> > >    leads to a use after free.
> > > 2) After device_initialize() then we need to use put_device() to
> > >    release the bus.  This will free the internal resources tied to the
> > >    device and call mcb_free_bus() which will free the rest.
> > >
> > > Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
> > > Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > >
> > 
> > Thanks applied
> 
> I don't think this was actually applied and that's a good thing because
> my patch wasn't correct.  It needs to call device_put() on both
> carrier and &bus->dev.
> 
> I'm going to send a v2 fix for this.

Actually, no...  My first patch was correct.  Calling put_device(&bus->dev);
will call the release function which will put the carrier.  My first
patch was correct.

:P

regards,
dan carpenter

Re: [PATCH] mcb: fix error handling in mcb_alloc_bus()

[Dan Carpenter]

On Tue, Jun 01, 2021 at 03:23:55PM +0200, Johannes Thumshirn wrote:
> 
> 
> Am 01.06.21 um 11:18 schrieb Dan Carpenter:
> > There are two bugs:
> > 1) If ida_simple_get() fails then this code calls put_device(carrier)
> >    but we haven't yet called get_device(carrier) and probably that
> >    leads to a use after free.
> > 2) After device_initialize() then we need to use put_device() to
> >    release the bus.  This will free the internal resources tied to the
> >    device and call mcb_free_bus() which will free the rest.
> >
> > Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
> > Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> 
> Thanks applied

This is still not in linux-next.

regards,
dan carpenter

Re: [PATCH] mcb: fix error handling in mcb_alloc_bus()

[Johannes Thumshirn]

Am 30.08.21 um 16:08 schrieb Dan Carpenter:
> On Tue, Jun 01, 2021 at 03:23:55PM +0200, Johannes Thumshirn wrote:
>>
>> Am 01.06.21 um 11:18 schrieb Dan Carpenter:
>>> There are two bugs:
>>> 1) If ida_simple_get() fails then this code calls put_device(carrier)
>>>    but we haven't yet called get_device(carrier) and probably that
>>>    leads to a use after free.
>>> 2) After device_initialize() then we need to use put_device() to
>>>    release the bus.  This will free the internal resources tied to the
>>>    device and call mcb_free_bus() which will free the rest.
>>>
>>> Fixes: 5d9e2ab9fea4 ("mcb: Implement bus->dev.release callback")
>>> Fixes: 18d288198099 ("mcb: Correctly initialize the bus's device")
>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>>
>> Thanks applied
> This is still not in linux-next.
>
> regards,
> dan carpenter

Hi Dan,

Greg asked me to resend the patch with Cc stable and I totally forgot to
do that, my bad.

I'll do that ASAP once the merge window opens again or earlier if Greg
is OK with it.

Byte,
    Johannes