2024-02-04 13:49:22

by Fedor Pchelkin

Subject: [PATCH] perf/x86/uncore: avoid null-ptr-deref on error in pmu_alloc_topology

If topology[die] array allocation fails then topology[die][idx] elements
can't be accessed on error path.

Checking this on the error path probably looks more readable than
decrementing the counter in the allocation loop.

Found by Linux Verification Center (linuxtesting.org).

Fixes: 4d13be8ab5d4 ("perf/x86/intel/uncore: Generalize IIO topology support")
Signed-off-by: Fedor Pchelkin <[email protected]>
---
arch/x86/events/intel/uncore_snbep.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
index a96496bef678..7d4deb9126be 100644
--- a/arch/x86/events/intel/uncore_snbep.c
+++ b/arch/x86/events/intel/uncore_snbep.c
@@ -3831,9 +3831,11 @@ static int pmu_alloc_topology(struct intel_uncore_type *type, int topology_type)
return 0;
clear:
for (; die >= 0; die--) {
- for (idx = 0; idx < type->num_boxes; idx++)
- kfree(topology[die][idx].untyped);
- kfree(topology[die]);
+ if (topology[die]) {
+ for (idx = 0; idx < type->num_boxes; idx++)
+ kfree(topology[die][idx].untyped);
+ kfree(topology[die]);
+ }
}
kfree(topology);
err:
--
2.39.2

2024-02-05 15:08:57

by Liang, Kan

Subject: Re: [PATCH] perf/x86/uncore: avoid null-ptr-deref on error in pmu_alloc_topology

On 2024-02-04 8:48 a.m., Fedor Pchelkin wrote:
> If topology[die] array allocation fails then topology[die][idx] elements
> can't be accessed on error path.
>
> Checking this on the error path probably looks more readable than
> decrementing the counter in the allocation loop.
>
> Found by Linux Verification Center (linuxtesting.org).
>
> Fixes: 4d13be8ab5d4 ("perf/x86/intel/uncore: Generalize IIO topology support")
> Signed-off-by: Fedor Pchelkin <[email protected]>
> ---

It seems the code just jumps to the wrong kfree on the error path.
Does the below patch work?

diff --git a/arch/x86/events/intel/uncore_snbep.c
b/arch/x86/events/intel/uncore_snbep.c
index 8250f0f59c2b..5481fd00d861 100644
--- a/arch/x86/events/intel/uncore_snbep.c
+++ b/arch/x86/events/intel/uncore_snbep.c
@@ -3808,7 +3808,7 @@ static int pmu_alloc_topology(struct
intel_uncore_type *type, int topology_type)
for (die = 0; die < uncore_max_dies(); die++) {
topology[die] = kcalloc(type->num_boxes, sizeof(**topology), GFP_KERNEL);
if (!topology[die])
- goto clear;
+ goto free_topology;
for (idx = 0; idx < type->num_boxes; idx++) {
topology[die][idx].untyped = kcalloc(type->num_boxes,
topology_size[topology_type],
@@ -3827,6 +3827,7 @@ static int pmu_alloc_topology(struct
intel_uncore_type *type, int topology_type)
kfree(topology[die][idx].untyped);
kfree(topology[die]);
}
+free_topology:
kfree(topology);
err:
return -ENOMEM;

Thanks,
Kan

> arch/x86/events/intel/uncore_snbep.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/events/intel/uncore_snbep.c b/arch/x86/events/intel/uncore_snbep.c
> index a96496bef678..7d4deb9126be 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -3831,9 +3831,11 @@ static int pmu_alloc_topology(struct intel_uncore_type *type, int topology_type)
> return 0;
> clear:
> for (; die >= 0; die--) {
> - for (idx = 0; idx < type->num_boxes; idx++)
> - kfree(topology[die][idx].untyped);
> - kfree(topology[die]);
> + if (topology[die]) {
> + for (idx = 0; idx < type->num_boxes; idx++)
> + kfree(topology[die][idx].untyped);
> + kfree(topology[die]);
> + }
> }
> kfree(topology);
> err:

2024-02-05 15:19:10

by Fedor Pchelkin

Subject: Re: Re: [PATCH] perf/x86/uncore: avoid null-ptr-deref on error in pmu_alloc_topology

Hello,

On 24/02/05 10:08AM, Liang, Kan wrote:
>
>
> On 2024-02-04 8:48 a.m., Fedor Pchelkin wrote:
> > If topology[die] array allocation fails then topology[die][idx] elements
> > can't be accessed on error path.
> >
> > Checking this on the error path probably looks more readable than
> > decrementing the counter in the allocation loop.
> >
> > Found by Linux Verification Center (linuxtesting.org).
> >
> > Fixes: 4d13be8ab5d4 ("perf/x86/intel/uncore: Generalize IIO topology support")
> > Signed-off-by: Fedor Pchelkin <[email protected]>
> > ---
>
> It seems the code just jumps to the wrong kfree on the error path.
> Does the below patch work?
>
> diff --git a/arch/x86/events/intel/uncore_snbep.c
> b/arch/x86/events/intel/uncore_snbep.c
> index 8250f0f59c2b..5481fd00d861 100644
> --- a/arch/x86/events/intel/uncore_snbep.c
> +++ b/arch/x86/events/intel/uncore_snbep.c
> @@ -3808,7 +3808,7 @@ static int pmu_alloc_topology(struct
> intel_uncore_type *type, int topology_type)
> for (die = 0; die < uncore_max_dies(); die++) {
> topology[die] = kcalloc(type->num_boxes, sizeof(**topology), GFP_KERNEL);
> if (!topology[die])
> - goto clear;
> + goto free_topology;
> for (idx = 0; idx < type->num_boxes; idx++) {
> topology[die][idx].untyped = kcalloc(type->num_boxes,
> topology_size[topology_type],
> @@ -3827,6 +3827,7 @@ static int pmu_alloc_topology(struct
> intel_uncore_type *type, int topology_type)
> kfree(topology[die][idx].untyped);
> kfree(topology[die]);
> }
> +free_topology:
> kfree(topology);
> err:
> return -ENOMEM;
>
> Thanks,
> Kan
>

In this way the already allocated topology[die] elements won't be freed.

--
Fedor

2024-02-05 15:32:53

by Liang, Kan

Subject: Re: [PATCH] perf/x86/uncore: avoid null-ptr-deref on error in pmu_alloc_topology

On 2024-02-05 10:18 a.m., Fedor Pchelkin wrote:
> Hello,
>
> On 24/02/05 10:08AM, Liang, Kan wrote:
>>
>>
>> On 2024-02-04 8:48 a.m., Fedor Pchelkin wrote:
>>> If topology[die] array allocation fails then topology[die][idx] elements
>>> can't be accessed on error path.
>>>
>>> Checking this on the error path probably looks more readable than
>>> decrementing the counter in the allocation loop.
>>>
>>> Found by Linux Verification Center (linuxtesting.org).
>>>
>>> Fixes: 4d13be8ab5d4 ("perf/x86/intel/uncore: Generalize IIO topology support")
>>> Signed-off-by: Fedor Pchelkin <[email protected]>
>>> ---
>>
>> It seems the code just jumps to the wrong kfree on the error path.
>> Does the below patch work?
>>
>> diff --git a/arch/x86/events/intel/uncore_snbep.c
>> b/arch/x86/events/intel/uncore_snbep.c
>> index 8250f0f59c2b..5481fd00d861 100644
>> --- a/arch/x86/events/intel/uncore_snbep.c
>> +++ b/arch/x86/events/intel/uncore_snbep.c
>> @@ -3808,7 +3808,7 @@ static int pmu_alloc_topology(struct
>> intel_uncore_type *type, int topology_type)
>> for (die = 0; die < uncore_max_dies(); die++) {
>> topology[die] = kcalloc(type->num_boxes, sizeof(**topology), GFP_KERNEL);
>> if (!topology[die])
>> - goto clear;
>> + goto free_topology;
>> for (idx = 0; idx < type->num_boxes; idx++) {
>> topology[die][idx].untyped = kcalloc(type->num_boxes,
>> topology_size[topology_type],
>> @@ -3827,6 +3827,7 @@ static int pmu_alloc_topology(struct
>> intel_uncore_type *type, int topology_type)
>> kfree(topology[die][idx].untyped);
>> kfree(topology[die]);
>> }
>> +free_topology:
>> kfree(topology);
>> err:
>> return -ENOMEM;
>>
>> Thanks,
>> Kan
>>
>
> In this way the already allocated topology[die] elements won't be freed.
>

Ah, right. The patch looks good to me.

Reviewed-by: Kan Liang <[email protected]>

Thanks,
Kan
> --
> Fedor
>