2022-05-30 08:13:18

by Muchun Song

Subject: [PATCH] mm: memory_hotplug: fix memory error handling

The device_unregister() is supposed to be used to unregister devices if
device_register() has succeed. And device_unregister() will put device.
The caller should not do it again, otherwise, the first call of
put_device() will drop the last reference count, then the next call
of device_unregister() will UAF on device.

Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
Signed-off-by: Muchun Song <[email protected]>
Cc: <[email protected]>
---
drivers/base/memory.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 7222ff9b5e05..084d67fd55cc 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -636,10 +636,9 @@ static int __add_memory_block(struct memory_block *memory)
}
ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
GFP_KERNEL));
- if (ret) {
- put_device(&memory->dev);
+ if (ret)
device_unregister(&memory->dev);
- }
+
return ret;
}

--
2.11.0

2022-05-30 11:41:46

by David Hildenbrand

Subject: Re: [PATCH] mm: memory_hotplug: fix memory error handling

On 30.05.22 07:33, Muchun Song wrote:
> The device_unregister() is supposed to be used to unregister devices if
> device_register() has succeed. And device_unregister() will put device.
> The caller should not do it again, otherwise, the first call of
> put_device() will drop the last reference count, then the next call
> of device_unregister() will UAF on device.
>
> Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
> Signed-off-by: Muchun Song <[email protected]>
> Cc: <[email protected]>
> ---
> drivers/base/memory.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 7222ff9b5e05..084d67fd55cc 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -636,10 +636,9 @@ static int __add_memory_block(struct memory_block *memory)
> }
> ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
> GFP_KERNEL));
> - if (ret) {
> - put_device(&memory->dev);
> + if (ret)
> device_unregister(&memory->dev);
> - }
> +
> return ret;
> }
>

See

https://lkml.kernel.org/r/d44c63d78affe844f020dc02ad6af29abc448fc4.1650611702.git.christophe.jaillet@wanadoo.fr

--
Thanks,

David / dhildenb

2022-05-30 14:12:59

by Muchun Song

Subject: Re: [PATCH] mm: memory_hotplug: fix memory error handling

On Mon, May 30, 2022 at 2:56 PM David Hildenbrand <[email protected]> wrote:
>
> On 30.05.22 07:33, Muchun Song wrote:
> > The device_unregister() is supposed to be used to unregister devices if
> > device_register() has succeed. And device_unregister() will put device.
> > The caller should not do it again, otherwise, the first call of
> > put_device() will drop the last reference count, then the next call
> > of device_unregister() will UAF on device.
> >
> > Fixes: 4fb6eabf1037 ("drivers/base/memory.c: cache memory blocks in xarray to accelerate lookup")
> > Signed-off-by: Muchun Song <[email protected]>
> > Cc: <[email protected]>
> > ---
> > drivers/base/memory.c | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> > index 7222ff9b5e05..084d67fd55cc 100644
> > --- a/drivers/base/memory.c
> > +++ b/drivers/base/memory.c
> > @@ -636,10 +636,9 @@ static int __add_memory_block(struct memory_block *memory)
> > }
> > ret = xa_err(xa_store(&memory_blocks, memory->dev.id, memory,
> > GFP_KERNEL));
> > - if (ret) {
> > - put_device(&memory->dev);
> > + if (ret)
> > device_unregister(&memory->dev);
> > - }
> > +
> > return ret;
> > }
> >
>
> See
>
> https://lkml.kernel.org/r/d44c63d78affe844f020dc02ad6af29abc448fc4.1650611702.git.christophe.jaillet@wanadoo.fr
>

I see. Good job by Christophe. Thanks David.