2023-06-10 02:17:08

by Sukrut Bellary

Subject: [PATCH] accel/qaic: Fix dereferencing freed memory

smatch warning:
drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
dereferencing freed memory 'obj->import_attach'

obj->import_attach is detached and freed using dma_buf_detach().
But used after free to decrease the dmabuf ref count using
dma_buf_put().

Fixes: ff13be830333 ("accel/qaic: Add datapath")
Signed-off-by: Sukrut Bellary <[email protected]>
---
drivers/accel/qaic/qaic_data.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
index e42c1f9ffff8..7cba4d680ea8 100644
--- a/drivers/accel/qaic/qaic_data.c
+++ b/drivers/accel/qaic/qaic_data.c
@@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struc
static void qaic_free_object(struct drm_gem_object *obj)
{
struct qaic_bo *bo = to_qaic_bo(obj);
+ struct dma_buf *dmabuf;

if (obj->import_attach) {
/* DMABUF/PRIME Path */
+ dmabuf = obj->import_attach->dmabuf;
dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach);
- dma_buf_put(obj->import_attach->dmabuf);
+ dma_buf_put(dmabuf);
} else {
/* Private buffer allocation path */
qaic_free_sgt(bo->sgt);
--
2.34.1

2023-06-12 11:55:34

by Christian König

Subject: Re: [PATCH] accel/qaic: Fix dereferencing freed memory

Am 10.06.23 um 04:12 schrieb Sukrut Bellary:
> smatch warning:
> drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
> dereferencing freed memory 'obj->import_attach'
>
> obj->import_attach is detached and freed using dma_buf_detach().
> But used after free to decrease the dmabuf ref count using
> dma_buf_put().
>
> Fixes: ff13be830333 ("accel/qaic: Add datapath")
> Signed-off-by: Sukrut Bellary <[email protected]>
> ---
> drivers/accel/qaic/qaic_data.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
> index e42c1f9ffff8..7cba4d680ea8 100644
> --- a/drivers/accel/qaic/qaic_data.c
> +++ b/drivers/accel/qaic/qaic_data.c
> @@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struc
> static void qaic_free_object(struct drm_gem_object *obj)
> {
> struct qaic_bo *bo = to_qaic_bo(obj);
> + struct dma_buf *dmabuf;

Maybe move that variable into the if.

>
> if (obj->import_attach) {
> /* DMABUF/PRIME Path */
> + dmabuf = obj->import_attach->dmabuf;
> dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach);
> - dma_buf_put(obj->import_attach->dmabuf);
> + dma_buf_put(dmabuf);

I strongly assume you are not using the GEM prime helpers for this?

Christian.

> } else {
> /* Private buffer allocation path */
> qaic_free_sgt(bo->sgt);

2023-06-12 12:59:49

by Pranjal Ramajor Asha Kanojiya

Subject: Re: [PATCH] accel/qaic: Fix dereferencing freed memory

On 6/10/2023 7:42 AM, Sukrut Bellary wrote:
> smatch warning:
> drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
> dereferencing freed memory 'obj->import_attach'
>
> obj->import_attach is detached and freed using dma_buf_detach().
> But used after free to decrease the dmabuf ref count using
> dma_buf_put().
>
> Fixes: ff13be830333 ("accel/qaic: Add datapath")
> Signed-off-by: Sukrut Bellary <[email protected]>
> ---
> drivers/accel/qaic/qaic_data.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
> index e42c1f9ffff8..7cba4d680ea8 100644
> --- a/drivers/accel/qaic/qaic_data.c
> +++ b/drivers/accel/qaic/qaic_data.c
> @@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct drm_gem_object *obj, struct vm_area_struc
> static void qaic_free_object(struct drm_gem_object *obj)
> {
> struct qaic_bo *bo = to_qaic_bo(obj);
> + struct dma_buf *dmabuf;
>
> if (obj->import_attach) {
> /* DMABUF/PRIME Path */
> + dmabuf = obj->import_attach->dmabuf;
> dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach);
> - dma_buf_put(obj->import_attach->dmabuf);
> + dma_buf_put(dmabuf);
> } else {
> /* Private buffer allocation path */
> qaic_free_sgt(bo->sgt);

Reviewed-by: Pranjal Ramajor Asha Kanojiya <[email protected]>

2023-06-12 13:35:36

by Pranjal Ramajor Asha Kanojiya

Subject: Re: [PATCH] accel/qaic: Fix dereferencing freed memory

On 6/12/2023 4:52 PM, Christian König wrote:
>
>
> Am 10.06.23 um 04:12 schrieb Sukrut Bellary:
>> smatch warning:
>>     drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
>>         dereferencing freed memory 'obj->import_attach'
>>
>> obj->import_attach is detached and freed using dma_buf_detach().
>> But used after free to decrease the dmabuf ref count using
>> dma_buf_put().
>>
>> Fixes: ff13be830333 ("accel/qaic: Add datapath")
>> Signed-off-by: Sukrut Bellary <[email protected]>
>> ---
>>   drivers/accel/qaic/qaic_data.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/accel/qaic/qaic_data.c
>> b/drivers/accel/qaic/qaic_data.c
>> index e42c1f9ffff8..7cba4d680ea8 100644
>> --- a/drivers/accel/qaic/qaic_data.c
>> +++ b/drivers/accel/qaic/qaic_data.c
>> @@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct
>> drm_gem_object *obj, struct vm_area_struc
>>   static void qaic_free_object(struct drm_gem_object *obj)
>>   {
>>       struct qaic_bo *bo = to_qaic_bo(obj);
>> +    struct dma_buf *dmabuf;
>
> Maybe move that variable into the if.
>
>>       if (obj->import_attach) {
>>           /* DMABUF/PRIME Path */
>> +        dmabuf = obj->import_attach->dmabuf;
>>           dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach);
>> -        dma_buf_put(obj->import_attach->dmabuf);
>> +        dma_buf_put(dmabuf);
>
> I strongly assume you are not using the GEM prime helpers for this?
>
> Christian.

Driver uses drm_gem_prime_fd_to_handle() helper function but it also
registers for ->gem_prime_import() which is internally called by
drm_gem_prime_fd_to_handle(). All the operations done in
gem_prime_import() are undone here.

>
>>       } else {
>>           /* Private buffer allocation path */
>>           qaic_free_sgt(bo->sgt);
>

2023-06-12 13:39:27

by Christian König

Subject: Re: [PATCH] accel/qaic: Fix dereferencing freed memory

Am 12.06.23 um 15:03 schrieb Pranjal Ramajor Asha Kanojiya:
>
>
> On 6/12/2023 4:52 PM, Christian König wrote:
>>
>>
>> Am 10.06.23 um 04:12 schrieb Sukrut Bellary:
>>> smatch warning:
>>>     drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
>>>         dereferencing freed memory 'obj->import_attach'
>>>
>>> obj->import_attach is detached and freed using dma_buf_detach().
>>> But used after free to decrease the dmabuf ref count using
>>> dma_buf_put().
>>>
>>> Fixes: ff13be830333 ("accel/qaic: Add datapath")
>>> Signed-off-by: Sukrut Bellary <[email protected]>
>>> ---
>>>   drivers/accel/qaic/qaic_data.c | 4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/accel/qaic/qaic_data.c
>>> b/drivers/accel/qaic/qaic_data.c
>>> index e42c1f9ffff8..7cba4d680ea8 100644
>>> --- a/drivers/accel/qaic/qaic_data.c
>>> +++ b/drivers/accel/qaic/qaic_data.c
>>> @@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct
>>> drm_gem_object *obj, struct vm_area_struc
>>>   static void qaic_free_object(struct drm_gem_object *obj)
>>>   {
>>>       struct qaic_bo *bo = to_qaic_bo(obj);
>>> +    struct dma_buf *dmabuf;
>>
>> Maybe move that variable into the if.
>>
>>>       if (obj->import_attach) {
>>>           /* DMABUF/PRIME Path */
>>> +        dmabuf = obj->import_attach->dmabuf;
>>>           dma_buf_detach(obj->import_attach->dmabuf,
>>> obj->import_attach);
>>> -        dma_buf_put(obj->import_attach->dmabuf);
>>> +        dma_buf_put(dmabuf);
>>
>> I strongly assume you are not using the GEM prime helpers for this?
>>
>> Christian.
>
> Driver uses drm_gem_prime_fd_to_handle() helper function but it also
> registers for ->gem_prime_import() which is internally called by
> drm_gem_prime_fd_to_handle(). All the operations done in
> gem_prime_import() are undone here.

Then why don't you use drm_prime_gem_destroy() which is the cleanup
helper for imports created by ->gem_prime_import() ?

That looks pretty much identical to what you do here manually.

Regards,
Christian.

>
>>
>>>       } else {
>>>           /* Private buffer allocation path */
>>>           qaic_free_sgt(bo->sgt);
>>

2023-06-12 15:45:38

by Jeffrey Hugo

Subject: Re: [PATCH] accel/qaic: Fix dereferencing freed memory

On 6/12/2023 7:21 AM, Christian König wrote:
> Am 12.06.23 um 15:03 schrieb Pranjal Ramajor Asha Kanojiya:
>>
>>
>> On 6/12/2023 4:52 PM, Christian König wrote:
>>>
>>>
>>> Am 10.06.23 um 04:12 schrieb Sukrut Bellary:
>>>> smatch warning:
>>>>     drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
>>>>         dereferencing freed memory 'obj->import_attach'
>>>>
>>>> obj->import_attach is detached and freed using dma_buf_detach().
>>>> But used after free to decrease the dmabuf ref count using
>>>> dma_buf_put().
>>>>
>>>> Fixes: ff13be830333 ("accel/qaic: Add datapath")
>>>> Signed-off-by: Sukrut Bellary <[email protected]>
>>>> ---
>>>>   drivers/accel/qaic/qaic_data.c | 4 +++-
>>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/accel/qaic/qaic_data.c
>>>> b/drivers/accel/qaic/qaic_data.c
>>>> index e42c1f9ffff8..7cba4d680ea8 100644
>>>> --- a/drivers/accel/qaic/qaic_data.c
>>>> +++ b/drivers/accel/qaic/qaic_data.c
>>>> @@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct
>>>> drm_gem_object *obj, struct vm_area_struc
>>>>   static void qaic_free_object(struct drm_gem_object *obj)
>>>>   {
>>>>       struct qaic_bo *bo = to_qaic_bo(obj);
>>>> +    struct dma_buf *dmabuf;
>>>
>>> Maybe move that variable into the if.
>>>
>>>>       if (obj->import_attach) {
>>>>           /* DMABUF/PRIME Path */
>>>> +        dmabuf = obj->import_attach->dmabuf;
>>>>           dma_buf_detach(obj->import_attach->dmabuf,
>>>> obj->import_attach);
>>>> -        dma_buf_put(obj->import_attach->dmabuf);
>>>> +        dma_buf_put(dmabuf);
>>>
>>> I strongly assume you are not using the GEM prime helpers for this?
>>>
>>> Christian.
>>
>> Driver uses drm_gem_prime_fd_to_handle() helper function but it also
>> registers for ->gem_prime_import() which is internally called by
>> drm_gem_prime_fd_to_handle(). All the operations done in
>> gem_prime_import() are undone here.
>
> Then why don't you use drm_prime_gem_destroy() which is the cleanup
> helper for imports created by ->gem_prime_import() ?
>
> That looks pretty much identical to what you do here manually.

I think destroy() wasn't used because we are new to DRM and sometimes
confused by the multitude of options. I appreciate the suggestion and
will follow up to see if destroy() will work here, or identify what
would prevent the use of it.

-Jeff

2023-06-12 16:10:27

by Pranjal Ramajor Asha Kanojiya

Subject: Re: [PATCH] accel/qaic: Fix dereferencing freed memory

On 6/12/2023 8:39 PM, Jeffrey Hugo wrote:
> On 6/12/2023 7:21 AM, Christian König wrote:
>> Am 12.06.23 um 15:03 schrieb Pranjal Ramajor Asha Kanojiya:
>>>
>>>
>>> On 6/12/2023 4:52 PM, Christian König wrote:
>>>>
>>>>
>>>> Am 10.06.23 um 04:12 schrieb Sukrut Bellary:
>>>>> smatch warning:
>>>>>     drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error:
>>>>>         dereferencing freed memory 'obj->import_attach'
>>>>>
>>>>> obj->import_attach is detached and freed using dma_buf_detach().
>>>>> But used after free to decrease the dmabuf ref count using
>>>>> dma_buf_put().
>>>>>
>>>>> Fixes: ff13be830333 ("accel/qaic: Add datapath")
>>>>> Signed-off-by: Sukrut Bellary <[email protected]>
>>>>> ---
>>>>>   drivers/accel/qaic/qaic_data.c | 4 +++-
>>>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/accel/qaic/qaic_data.c
>>>>> b/drivers/accel/qaic/qaic_data.c
>>>>> index e42c1f9ffff8..7cba4d680ea8 100644
>>>>> --- a/drivers/accel/qaic/qaic_data.c
>>>>> +++ b/drivers/accel/qaic/qaic_data.c
>>>>> @@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct
>>>>> drm_gem_object *obj, struct vm_area_struc
>>>>>   static void qaic_free_object(struct drm_gem_object *obj)
>>>>>   {
>>>>>       struct qaic_bo *bo = to_qaic_bo(obj);
>>>>> +    struct dma_buf *dmabuf;
>>>>
>>>> Maybe move that variable into the if.
>>>>
>>>>>       if (obj->import_attach) {
>>>>>           /* DMABUF/PRIME Path */
>>>>> +        dmabuf = obj->import_attach->dmabuf;
>>>>>           dma_buf_detach(obj->import_attach->dmabuf,
>>>>> obj->import_attach);
>>>>> -        dma_buf_put(obj->import_attach->dmabuf);
>>>>> +        dma_buf_put(dmabuf);
>>>>
>>>> I strongly assume you are not using the GEM prime helpers for this?
>>>>
>>>> Christian.
>>>
>>> Driver uses drm_gem_prime_fd_to_handle() helper function but it also
>>> registers for ->gem_prime_import() which is internally called by
>>> drm_gem_prime_fd_to_handle(). All the operations done in
>>> gem_prime_import() are undone here.
>>
>> Then why don't you use drm_prime_gem_destroy() which is the cleanup
>> helper for imports created by ->gem_prime_import() ?
>>
>> That looks pretty much identical to what you do here manually.
>
> I think destroy() wasn't used because we are new to DRM and sometimes
> confused by the multitude of options.  I appreciate the suggestion and
> will follow up to see if destroy() will work here, or identify what
> would prevent the use of it.
>
> -Jeff

Thank you Christian for your suggestion. I agree with you driver can use
drm_prime_gem_destroy() here.