[PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[Harshit Mogalapalli]

In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being freed. Fix this by reordering the kfree() post the dereference.

Fixes: 9d1d36268f3d ("platform/x86: ISST: Support partitioned systems")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
---
This is found by smatch and only compile tested.
---
 drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
index 7bac7841ff0a..7fa360073f6e 100644
--- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
+++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
@@ -1610,8 +1610,8 @@ void tpmi_sst_dev_remove(struct auxiliary_device *auxdev)
 	tpmi_sst->partition_mask_current &= ~BIT(plat_info->partition);
 	/* Free the package instance when the all partitions are removed */
 	if (!tpmi_sst->partition_mask_current) {
-		kfree(tpmi_sst);
 		isst_common.sst_inst[tpmi_sst->package_id] = NULL;
+		kfree(tpmi_sst);
 	}
 	mutex_unlock(&isst_tpmi_dev_lock);
 }
-- 
2.39.3

Re: [PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[Hans de Goede]

Hi,

On 5/14/24 11:26 AM, Harshit Mogalapalli wrote:
> In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being freed. Fix this by reordering the kfree() post the dereference.
> 
> Fixes: 9d1d36268f3d ("platform/x86: ISST: Support partitioned systems")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>

This looks obviously correct to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

Still would be nice if one of the Intel maintainers for this
can ack it.

Either way I'll merge this for the first pdx86 fixes pull-request
for 6.10 (when I get around to merging the first round of fixes).

Regards,

Hans




> ---
> This is found by smatch and only compile tested.
> ---
>  drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> index 7bac7841ff0a..7fa360073f6e 100644
> --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> @@ -1610,8 +1610,8 @@ void tpmi_sst_dev_remove(struct auxiliary_device *auxdev)
>  	tpmi_sst->partition_mask_current &= ~BIT(plat_info->partition);
>  	/* Free the package instance when the all partitions are removed */
>  	if (!tpmi_sst->partition_mask_current) {
> -		kfree(tpmi_sst);
>  		isst_common.sst_inst[tpmi_sst->package_id] = NULL;
> +		kfree(tpmi_sst);
>  	}
>  	mutex_unlock(&isst_tpmi_dev_lock);
>  }

Re: [PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[Markus Elfring]

> In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being freed. Fix this by reordering the kfree() post the dereference.

I suggest to take preferred line lengths better into account
also for such a change description.
Thus the second sentence should be put into a subsequent line.
How do you think about the following wording approach?

   Move a kfree() call behind an assignment statement in the affected if branch.

Regards,
Markus

Re: [PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[srinivas pandruvada]

On Tue, 2024-05-14 at 02:26 -0700, Harshit Mogalapalli wrote:
> In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being freed.
> Fix this by reordering the kfree() post the dereference.
> 
> Fixes: 9d1d36268f3d ("platform/x86: ISST: Support partitioned
> systems")
> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>

> ---
> This is found by smatch and only compile tested.
> ---
>  drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git
> a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> index 7bac7841ff0a..7fa360073f6e 100644
> --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> @@ -1610,8 +1610,8 @@ void tpmi_sst_dev_remove(struct
> auxiliary_device *auxdev)
>         tpmi_sst->partition_mask_current &= ~BIT(plat_info-
> >partition);
>         /* Free the package instance when the all partitions are
> removed */
>         if (!tpmi_sst->partition_mask_current) {
> -               kfree(tpmi_sst);
>                 isst_common.sst_inst[tpmi_sst->package_id] = NULL;
> +               kfree(tpmi_sst);
>         }
>         mutex_unlock(&isst_tpmi_dev_lock);
>  }

Re: [PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[srinivas pandruvada]

On Fri, 2024-05-17 at 07:31 -0700, srinivas pandruvada wrote:
> On Tue, 2024-05-14 at 02:26 -0700, Harshit Mogalapalli wrote:
> > In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being
> > freed.
> > Fix this by reordering the kfree() post the dereference.
> > 
> > Fixes: 9d1d36268f3d ("platform/x86: ISST: Support partitioned
> > systems")
> > Signed-off-by: Harshit Mogalapalli
> > <harshit.m.mogalapalli@oracle.com>
> Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> 
I realized the line length is 127 chars in commit description.
Please fix that and run checkpatch.pl before posting again.

Thanks,
Srinivas

> > ---
> > This is found by smatch and only compile tested.
> > ---
> >  drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git
> > a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > index 7bac7841ff0a..7fa360073f6e 100644
> > --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
> > @@ -1610,8 +1610,8 @@ void tpmi_sst_dev_remove(struct
> > auxiliary_device *auxdev)
> >         tpmi_sst->partition_mask_current &= ~BIT(plat_info-
> > > partition);
> >         /* Free the package instance when the all partitions are
> > removed */
> >         if (!tpmi_sst->partition_mask_current) {
> > -               kfree(tpmi_sst);
> >                 isst_common.sst_inst[tpmi_sst->package_id] = NULL;
> > +               kfree(tpmi_sst);
> >         }
> >         mutex_unlock(&isst_tpmi_dev_lock);
> >  }
> 

Re: [PATCH] platform/x86: ISST: fix use-after-free in tpmi_sst_dev_remove()

[Harshit Mogalapalli]

On 17/05/24 20:03, srinivas pandruvada wrote:
> On Fri, 2024-05-17 at 07:31 -0700, srinivas pandruvada wrote:
>> On Tue, 2024-05-14 at 02:26 -0700, Harshit Mogalapalli wrote:
>>> In tpmi_sst_dev_remove(), tpmi_sst is dereferenced after being
>>> freed.
>>> Fix this by reordering the kfree() post the dereference.
>>>
>>> Fixes: 9d1d36268f3d ("platform/x86: ISST: Support partitioned
>>> systems")
>>> Signed-off-by: Harshit Mogalapalli
>>> <harshit.m.mogalapalli@oracle.com>
>> Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
>>
> I realized the line length is 127 chars in commit description.
> Please fix that and run checkpatch.pl before posting again.
> 

Thanks for the ACK.

Sorry I usually run checkpatch.pl, but somehow missed noticing the 
error. Will send it with the commit message fixup.

Thanks,
Harshit
> Thanks,
> Srinivas
> 
>>> ---
>>> This is found by smatch and only compile tested.
>>> ---
>>>   drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git
>>> a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
>>> b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
>>> index 7bac7841ff0a..7fa360073f6e 100644
>>> --- a/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
>>> +++ b/drivers/platform/x86/intel/speed_select_if/isst_tpmi_core.c
>>> @@ -1610,8 +1610,8 @@ void tpmi_sst_dev_remove(struct
>>> auxiliary_device *auxdev)
>>>          tpmi_sst->partition_mask_current &= ~BIT(plat_info-
>>>> partition);
>>>          /* Free the package instance when the all partitions are
>>> removed */
>>>          if (!tpmi_sst->partition_mask_current) {
>>> -               kfree(tpmi_sst);
>>>                  isst_common.sst_inst[tpmi_sst->package_id] = NULL;
>>> +               kfree(tpmi_sst);
>>>          }
>>>          mutex_unlock(&isst_tpmi_dev_lock);
>>>   }
>>
>