drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-)
This commit prevents the possibility of a use after free issue in the
GROUP_CREATE ioctl function, which arose as pointer to the group is
accessed in that ioctl function after storing it in the Xarray.
A malicious userspace can second guess the handle of a group and try
to call GROUP_DESTROY ioctl from another thread around the same time
as GROUP_CREATE ioctl.
To prevent the use after free exploit, this commit uses a mark on an
entry of group pool Xarray which is added just before returning from
the GROUP_CREATE ioctl function. The mark is checked for all ioctls
that specify the group handle and so userspace won't be abe to delete
a group that isn't marked yet.
Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Akash Goel <akash.goel@arm.com>
---
drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index b834123a6560..a6b8024e1a3c 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -779,6 +779,12 @@ struct panthor_job_profiling_data {
*/
#define MAX_GROUPS_PER_POOL 128
+/*
+ * Mark added on an entry of group pool Xarray to identify if the group has
+ * been fully initialized and can be accessed elsewhere in the driver code.
+ */
+#define GROUP_REGISTERED XA_MARK_1
+
/**
* struct panthor_group_pool - Group pool
*
@@ -3007,7 +3013,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
return;
xa_lock(&gpool->xa);
- xa_for_each(&gpool->xa, i, group) {
+ xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
guard(spinlock)(&group->fdinfo.lock);
pfile->stats.cycles += group->fdinfo.data.cycles;
pfile->stats.time += group->fdinfo.data.time;
@@ -3727,6 +3733,8 @@ int panthor_group_create(struct panthor_file *pfile,
group_init_task_info(group);
+ xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);
+
return gid;
err_erase_gid:
@@ -3744,6 +3752,9 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
struct panthor_scheduler *sched = ptdev->scheduler;
struct panthor_group *group;
+ if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))
+ return -EINVAL;
+
group = xa_erase(&gpool->xa, group_handle);
if (!group)
return -EINVAL;
@@ -3769,12 +3780,12 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
}
static struct panthor_group *group_from_handle(struct panthor_group_pool *pool,
- u32 group_handle)
+ unsigned long group_handle)
{
struct panthor_group *group;
xa_lock(&pool->xa);
- group = group_get(xa_load(&pool->xa, group_handle));
+ group = group_get(xa_find(&pool->xa, &group_handle, group_handle, GROUP_REGISTERED));
xa_unlock(&pool->xa);
return group;
@@ -3861,7 +3872,7 @@ panthor_fdinfo_gather_group_mem_info(struct panthor_file *pfile,
return;
xa_lock(&gpool->xa);
- xa_for_each(&gpool->xa, i, group) {
+ xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
stats->resident += group->fdinfo.kbo_sizes;
if (group->csg_id >= 0)
stats->active += group->fdinfo.kbo_sizes;
--
2.25.1On 27/11/2025 08:12, Akash Goel wrote:
> This commit prevents the possibility of a use after free issue in the
> GROUP_CREATE ioctl function, which arose as pointer to the group is
> accessed in that ioctl function after storing it in the Xarray.
> A malicious userspace can second guess the handle of a group and try
> to call GROUP_DESTROY ioctl from another thread around the same time
> as GROUP_CREATE ioctl.
>
> To prevent the use after free exploit, this commit uses a mark on an
> entry of group pool Xarray which is added just before returning from
> the GROUP_CREATE ioctl function. The mark is checked for all ioctls
> that specify the group handle and so userspace won't be abe to delete
> a group that isn't marked yet.
>
> Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Akash Goel <akash.goel@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
I *think* this should have a...
Fixes: d2624d90a0b7 ("drm/panthor: assign unique names to queues")
... as I don't believe it was a problem before the rearrangement that
happened there.
Thanks,
Steve
> ---
> drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index b834123a6560..a6b8024e1a3c 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -779,6 +779,12 @@ struct panthor_job_profiling_data {
> */
> #define MAX_GROUPS_PER_POOL 128
>
> +/*
> + * Mark added on an entry of group pool Xarray to identify if the group has
> + * been fully initialized and can be accessed elsewhere in the driver code.
> + */
> +#define GROUP_REGISTERED XA_MARK_1
> +
> /**
> * struct panthor_group_pool - Group pool
> *
> @@ -3007,7 +3013,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
> return;
>
> xa_lock(&gpool->xa);
> - xa_for_each(&gpool->xa, i, group) {
> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
> guard(spinlock)(&group->fdinfo.lock);
> pfile->stats.cycles += group->fdinfo.data.cycles;
> pfile->stats.time += group->fdinfo.data.time;
> @@ -3727,6 +3733,8 @@ int panthor_group_create(struct panthor_file *pfile,
>
> group_init_task_info(group);
>
> + xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);
> +
> return gid;
>
> err_erase_gid:
> @@ -3744,6 +3752,9 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
> struct panthor_scheduler *sched = ptdev->scheduler;
> struct panthor_group *group;
>
> + if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))
> + return -EINVAL;
> +
> group = xa_erase(&gpool->xa, group_handle);
> if (!group)
> return -EINVAL;
> @@ -3769,12 +3780,12 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
> }
>
> static struct panthor_group *group_from_handle(struct panthor_group_pool *pool,
> - u32 group_handle)
> + unsigned long group_handle)
> {
> struct panthor_group *group;
>
> xa_lock(&pool->xa);
> - group = group_get(xa_load(&pool->xa, group_handle));
> + group = group_get(xa_find(&pool->xa, &group_handle, group_handle, GROUP_REGISTERED));
> xa_unlock(&pool->xa);
>
> return group;
> @@ -3861,7 +3872,7 @@ panthor_fdinfo_gather_group_mem_info(struct panthor_file *pfile,
> return;
>
> xa_lock(&gpool->xa);
> - xa_for_each(&gpool->xa, i, group) {
> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
> stats->resident += group->fdinfo.kbo_sizes;
> if (group->csg_id >= 0)
> stats->active += group->fdinfo.kbo_sizes;
On Thu, 27 Nov 2025 16:02:15 +0000
Steven Price <steven.price@arm.com> wrote:
> On 27/11/2025 08:12, Akash Goel wrote:
> > This commit prevents the possibility of a use after free issue in the
> > GROUP_CREATE ioctl function, which arose as pointer to the group is
> > accessed in that ioctl function after storing it in the Xarray.
> > A malicious userspace can second guess the handle of a group and try
> > to call GROUP_DESTROY ioctl from another thread around the same time
> > as GROUP_CREATE ioctl.
> >
> > To prevent the use after free exploit, this commit uses a mark on an
> > entry of group pool Xarray which is added just before returning from
> > the GROUP_CREATE ioctl function. The mark is checked for all ioctls
> > that specify the group handle and so userspace won't be abe to delete
> > a group that isn't marked yet.
> >
> > Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
> > Signed-off-by: Akash Goel <akash.goel@arm.com>
>
> Reviewed-by: Steven Price <steven.price@arm.com>
>
> I *think* this should have a...
>
> Fixes: d2624d90a0b7 ("drm/panthor: assign unique names to queues")
>
> ... as I don't believe it was a problem before the rearrangement that
> happened there.
Oh, yeah, I didn't notice the commit was missing a Fixes tag, and
you're correct about the offending commit.
>
> Thanks,
> Steve
>
> > ---
> > drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++----
> > 1 file changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> > index b834123a6560..a6b8024e1a3c 100644
> > --- a/drivers/gpu/drm/panthor/panthor_sched.c
> > +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> > @@ -779,6 +779,12 @@ struct panthor_job_profiling_data {
> > */
> > #define MAX_GROUPS_PER_POOL 128
> >
> > +/*
> > + * Mark added on an entry of group pool Xarray to identify if the group has
> > + * been fully initialized and can be accessed elsewhere in the driver code.
> > + */
> > +#define GROUP_REGISTERED XA_MARK_1
> > +
> > /**
> > * struct panthor_group_pool - Group pool
> > *
> > @@ -3007,7 +3013,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
> > return;
> >
> > xa_lock(&gpool->xa);
> > - xa_for_each(&gpool->xa, i, group) {
> > + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
> > guard(spinlock)(&group->fdinfo.lock);
> > pfile->stats.cycles += group->fdinfo.data.cycles;
> > pfile->stats.time += group->fdinfo.data.time;
> > @@ -3727,6 +3733,8 @@ int panthor_group_create(struct panthor_file *pfile,
> >
> > group_init_task_info(group);
> >
> > + xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);
> > +
> > return gid;
> >
> > err_erase_gid:
> > @@ -3744,6 +3752,9 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
> > struct panthor_scheduler *sched = ptdev->scheduler;
> > struct panthor_group *group;
> >
> > + if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))
> > + return -EINVAL;
> > +
> > group = xa_erase(&gpool->xa, group_handle);
> > if (!group)
> > return -EINVAL;
> > @@ -3769,12 +3780,12 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
> > }
> >
> > static struct panthor_group *group_from_handle(struct panthor_group_pool *pool,
> > - u32 group_handle)
> > + unsigned long group_handle)
> > {
> > struct panthor_group *group;
> >
> > xa_lock(&pool->xa);
> > - group = group_get(xa_load(&pool->xa, group_handle));
> > + group = group_get(xa_find(&pool->xa, &group_handle, group_handle, GROUP_REGISTERED));
> > xa_unlock(&pool->xa);
> >
> > return group;
> > @@ -3861,7 +3872,7 @@ panthor_fdinfo_gather_group_mem_info(struct panthor_file *pfile,
> > return;
> >
> > xa_lock(&gpool->xa);
> > - xa_for_each(&gpool->xa, i, group) {
> > + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
> > stats->resident += group->fdinfo.kbo_sizes;
> > if (group->csg_id >= 0)
> > stats->active += group->fdinfo.kbo_sizes;
>
Hi Steve, Boris
On 11/27/25 16:08, Boris Brezillon wrote:
> On Thu, 27 Nov 2025 16:02:15 +0000
> Steven Price <steven.price@arm.com> wrote:
>
>> On 27/11/2025 08:12, Akash Goel wrote:
>>> This commit prevents the possibility of a use after free issue in the
>>> GROUP_CREATE ioctl function, which arose as pointer to the group is
>>> accessed in that ioctl function after storing it in the Xarray.
>>> A malicious userspace can second guess the handle of a group and try
>>> to call GROUP_DESTROY ioctl from another thread around the same time
>>> as GROUP_CREATE ioctl.
>>>
>>> To prevent the use after free exploit, this commit uses a mark on an
>>> entry of group pool Xarray which is added just before returning from
>>> the GROUP_CREATE ioctl function. The mark is checked for all ioctls
>>> that specify the group handle and so userspace won't be abe to delete
>>> a group that isn't marked yet.
>>>
>>> Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
>>> Signed-off-by: Akash Goel <akash.goel@arm.com>
>>
>> Reviewed-by: Steven Price <steven.price@arm.com>
>>
>> I *think* this should have a...
>>
>> Fixes: d2624d90a0b7 ("drm/panthor: assign unique names to queues")
>>
>> ... as I don't believe it was a problem before the rearrangement that
>> happened there.
>
> Oh, yeah, I didn't notice the commit was missing a Fixes tag, and
> you're correct about the offending commit.
>
Sorry for not adding the Fixes tag.
I think the problem has been present since the beginning and the Fixes
tag should be
Fixes: de85488138247 ("drm/panthor: Add the scheduler logical block")
Initially the code was like this,
ret = xa_alloc(&gpool->xa, &gid, group, XA_LIMIT(1,
MAX_GROUPS_PER_POOL), GFP_KERNEL);
if (ret)
goto err_put_group;
mutex_lock(&sched->reset.lock);
if (atomic_read(&sched->reset.in_progress)) {
panthor_group_stop(group);
} else {
mutex_lock(&sched->lock);
list_add_tail(&group->run_node,
&sched->groups.idle[group->priority]);
mutex_unlock(&sched->lock);
}
mutex_unlock(&sched->reset.lock);
return gid;
If the GROUP_CREATE ioctl thread somehow gets preempted immediately
after xa_alloc(), then another thread might succeed in freeing the group
through GROUP_DESTROY ioctl.
Initially it would have been very difficult to trigger the UAF, but
d2624d90a0b7 ("drm/panthor: assign unique names to queues") would have
made the code more susceptible to UAF.
Please kindly correct me if I interpreted things incorrectly.
Will accordingly send a v2.
Best regards
Akash
>>
>> Thanks,
>> Steve
>>
>>> ---
>>> drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++----
>>> 1 file changed, 15 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
>>> index b834123a6560..a6b8024e1a3c 100644
>>> --- a/drivers/gpu/drm/panthor/panthor_sched.c
>>> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
>>> @@ -779,6 +779,12 @@ struct panthor_job_profiling_data {
>>> */
>>> #define MAX_GROUPS_PER_POOL 128
>>>
>>> +/*
>>> + * Mark added on an entry of group pool Xarray to identify if the group has
>>> + * been fully initialized and can be accessed elsewhere in the driver code.
>>> + */
>>> +#define GROUP_REGISTERED XA_MARK_1
>>> +
>>> /**
>>> * struct panthor_group_pool - Group pool
>>> *
>>> @@ -3007,7 +3013,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
>>> return;
>>>
>>> xa_lock(&gpool->xa);
>>> - xa_for_each(&gpool->xa, i, group) {
>>> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
>>> guard(spinlock)(&group->fdinfo.lock);
>>> pfile->stats.cycles += group->fdinfo.data.cycles;
>>> pfile->stats.time += group->fdinfo.data.time;
>>> @@ -3727,6 +3733,8 @@ int panthor_group_create(struct panthor_file *pfile,
>>>
>>> group_init_task_info(group);
>>>
>>> + xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);
>>> +
>>> return gid;
>>>
>>> err_erase_gid:
>>> @@ -3744,6 +3752,9 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
>>> struct panthor_scheduler *sched = ptdev->scheduler;
>>> struct panthor_group *group;
>>>
>>> + if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))
>>> + return -EINVAL;
>>> +
>>> group = xa_erase(&gpool->xa, group_handle);
>>> if (!group)
>>> return -EINVAL;
>>> @@ -3769,12 +3780,12 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
>>> }
>>>
>>> static struct panthor_group *group_from_handle(struct panthor_group_pool *pool,
>>> - u32 group_handle)
>>> + unsigned long group_handle)
>>> {
>>> struct panthor_group *group;
>>>
>>> xa_lock(&pool->xa);
>>> - group = group_get(xa_load(&pool->xa, group_handle));
>>> + group = group_get(xa_find(&pool->xa, &group_handle, group_handle, GROUP_REGISTERED));
>>> xa_unlock(&pool->xa);
>>>
>>> return group;
>>> @@ -3861,7 +3872,7 @@ panthor_fdinfo_gather_group_mem_info(struct panthor_file *pfile,
>>> return;
>>>
>>> xa_lock(&gpool->xa);
>>> - xa_for_each(&gpool->xa, i, group) {
>>> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
>>> stats->resident += group->fdinfo.kbo_sizes;
>>> if (group->csg_id >= 0)
>>> stats->active += group->fdinfo.kbo_sizes;
>>
>
On 27/11/2025 16:32, Akash Goel wrote:
> Hi Steve, Boris
>
> On 11/27/25 16:08, Boris Brezillon wrote:
>> On Thu, 27 Nov 2025 16:02:15 +0000
>> Steven Price <steven.price@arm.com> wrote:
>>
>>> On 27/11/2025 08:12, Akash Goel wrote:
>>>> This commit prevents the possibility of a use after free issue in the
>>>> GROUP_CREATE ioctl function, which arose as pointer to the group is
>>>> accessed in that ioctl function after storing it in the Xarray.
>>>> A malicious userspace can second guess the handle of a group and try
>>>> to call GROUP_DESTROY ioctl from another thread around the same time
>>>> as GROUP_CREATE ioctl.
>>>>
>>>> To prevent the use after free exploit, this commit uses a mark on an
>>>> entry of group pool Xarray which is added just before returning from
>>>> the GROUP_CREATE ioctl function. The mark is checked for all ioctls
>>>> that specify the group handle and so userspace won't be abe to delete
>>>> a group that isn't marked yet.
>>>>
>>>> Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
>>>> Signed-off-by: Akash Goel <akash.goel@arm.com>
>>>
>>> Reviewed-by: Steven Price <steven.price@arm.com>
>>>
>>> I *think* this should have a...
>>>
>>> Fixes: d2624d90a0b7 ("drm/panthor: assign unique names to queues")
>>>
>>> ... as I don't believe it was a problem before the rearrangement that
>>> happened there.
>>
>> Oh, yeah, I didn't notice the commit was missing a Fixes tag, and
>> you're correct about the offending commit.
>>
>
> Sorry for not adding the Fixes tag.
>
>
> I think the problem has been present since the beginning and the Fixes
> tag should be
>
> Fixes: de85488138247 ("drm/panthor: Add the scheduler logical block")
>
>
> Initially the code was like this,
>
>
> ret = xa_alloc(&gpool->xa, &gid, group, XA_LIMIT(1,
> MAX_GROUPS_PER_POOL), GFP_KERNEL);
> if (ret)
> goto err_put_group;
>
> mutex_lock(&sched->reset.lock);
> if (atomic_read(&sched->reset.in_progress)) {
> panthor_group_stop(group);
> } else {
> mutex_lock(&sched->lock);
> list_add_tail(&group->run_node,
> &sched->groups.idle[group->priority]);
> mutex_unlock(&sched->lock);
> }
> mutex_unlock(&sched->reset.lock);
>
> return gid;
>
> If the GROUP_CREATE ioctl thread somehow gets preempted immediately
> after xa_alloc(), then another thread might succeed in freeing the group
> through GROUP_DESTROY ioctl.
>
> Initially it would have been very difficult to trigger the UAF, but
> d2624d90a0b7 ("drm/panthor: assign unique names to queues") would have
> made the code more susceptible to UAF.
>
> Please kindly correct me if I interpreted things incorrectly.
No, looking at this again, I think you're correct - I saw the locks and
didn't think through that they don't actually protect us against the
racing destroy. I'm not sure why that code didn't have the xa_alloc() as
the final call.
> Will accordingly send a v2.
Thanks!
Steve
> Best regards
> Akash
>
>
>>>
>>> Thanks,
>>> Steve
>>>
>>>> ---
>>>> drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++----
>>>> 1 file changed, 15 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/
>>>> drm/panthor/panthor_sched.c
>>>> index b834123a6560..a6b8024e1a3c 100644
>>>> --- a/drivers/gpu/drm/panthor/panthor_sched.c
>>>> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
>>>> @@ -779,6 +779,12 @@ struct panthor_job_profiling_data {
>>>> */
>>>> #define MAX_GROUPS_PER_POOL 128
>>>> +/*
>>>> + * Mark added on an entry of group pool Xarray to identify if the
>>>> group has
>>>> + * been fully initialized and can be accessed elsewhere in the
>>>> driver code.
>>>> + */
>>>> +#define GROUP_REGISTERED XA_MARK_1
>>>> +
>>>> /**
>>>> * struct panthor_group_pool - Group pool
>>>> *
>>>> @@ -3007,7 +3013,7 @@ void
>>>> panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
>>>> return;
>>>> xa_lock(&gpool->xa);
>>>> - xa_for_each(&gpool->xa, i, group) {
>>>> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
>>>> guard(spinlock)(&group->fdinfo.lock);
>>>> pfile->stats.cycles += group->fdinfo.data.cycles;
>>>> pfile->stats.time += group->fdinfo.data.time;
>>>> @@ -3727,6 +3733,8 @@ int panthor_group_create(struct panthor_file
>>>> *pfile,
>>>> group_init_task_info(group);
>>>> + xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);
>>>> +
>>>> return gid;
>>>> err_erase_gid:
>>>> @@ -3744,6 +3752,9 @@ int panthor_group_destroy(struct panthor_file
>>>> *pfile, u32 group_handle)
>>>> struct panthor_scheduler *sched = ptdev->scheduler;
>>>> struct panthor_group *group;
>>>> + if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))
>>>> + return -EINVAL;
>>>> +
>>>> group = xa_erase(&gpool->xa, group_handle);
>>>> if (!group)
>>>> return -EINVAL;
>>>> @@ -3769,12 +3780,12 @@ int panthor_group_destroy(struct
>>>> panthor_file *pfile, u32 group_handle)
>>>> }
>>>> static struct panthor_group *group_from_handle(struct
>>>> panthor_group_pool *pool,
>>>> - u32 group_handle)
>>>> + unsigned long group_handle)
>>>> {
>>>> struct panthor_group *group;
>>>> xa_lock(&pool->xa);
>>>> - group = group_get(xa_load(&pool->xa, group_handle));
>>>> + group = group_get(xa_find(&pool->xa, &group_handle,
>>>> group_handle, GROUP_REGISTERED));
>>>> xa_unlock(&pool->xa);
>>>> return group;
>>>> @@ -3861,7 +3872,7 @@ panthor_fdinfo_gather_group_mem_info(struct
>>>> panthor_file *pfile,
>>>> return;
>>>> xa_lock(&gpool->xa);
>>>> - xa_for_each(&gpool->xa, i, group) {
>>>> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
>>>> stats->resident += group->fdinfo.kbo_sizes;
>>>> if (group->csg_id >= 0)
>>>> stats->active += group->fdinfo.kbo_sizes;
>>>
>>
On 27/11/2025 16:08, Boris Brezillon wrote:
> On Thu, 27 Nov 2025 16:02:15 +0000
> Steven Price <steven.price@arm.com> wrote:
>
>> On 27/11/2025 08:12, Akash Goel wrote:
>>> This commit prevents the possibility of a use after free issue in the
>>> GROUP_CREATE ioctl function, which arose as pointer to the group is
>>> accessed in that ioctl function after storing it in the Xarray.
>>> A malicious userspace can second guess the handle of a group and try
>>> to call GROUP_DESTROY ioctl from another thread around the same time
>>> as GROUP_CREATE ioctl.
>>>
>>> To prevent the use after free exploit, this commit uses a mark on an
>>> entry of group pool Xarray which is added just before returning from
>>> the GROUP_CREATE ioctl function. The mark is checked for all ioctls
>>> that specify the group handle and so userspace won't be abe to delete
>>> a group that isn't marked yet.
>>>
>>> Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
>>> Signed-off-by: Akash Goel <akash.goel@arm.com>
dim (rightly) complains about these tags. Co-developed-by is a tricky
one because it needs to be paired with an identical Signed-off-by (see
the docs[1]) because it states that Boris has written some of the code.
[1]
https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html#when-to-use-acked-by-cc-and-co-developed-by
>>
>> Reviewed-by: Steven Price <steven.price@arm.com>
>>
>> I *think* this should have a...
>>
>> Fixes: d2624d90a0b7 ("drm/panthor: assign unique names to queues")
>>
>> ... as I don't believe it was a problem before the rearrangement that
>> happened there.
>
> Oh, yeah, I didn't notice the commit was missing a Fixes tag, and
> you're correct about the offending commit.
I feel a bit like the tag police, but it's good to get them right so the
backports go smoothly (in this case we shouldn't need a backport and it
can go into drm-misc-next-fixes).
Thanks,
Steve
>>
>> Thanks,
>> Steve
>>
>>> ---
>>> drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++----
>>> 1 file changed, 15 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
>>> index b834123a6560..a6b8024e1a3c 100644
>>> --- a/drivers/gpu/drm/panthor/panthor_sched.c
>>> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
>>> @@ -779,6 +779,12 @@ struct panthor_job_profiling_data {
>>> */
>>> #define MAX_GROUPS_PER_POOL 128
>>>
>>> +/*
>>> + * Mark added on an entry of group pool Xarray to identify if the group has
>>> + * been fully initialized and can be accessed elsewhere in the driver code.
>>> + */
>>> +#define GROUP_REGISTERED XA_MARK_1
>>> +
>>> /**
>>> * struct panthor_group_pool - Group pool
>>> *
>>> @@ -3007,7 +3013,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
>>> return;
>>>
>>> xa_lock(&gpool->xa);
>>> - xa_for_each(&gpool->xa, i, group) {
>>> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
>>> guard(spinlock)(&group->fdinfo.lock);
>>> pfile->stats.cycles += group->fdinfo.data.cycles;
>>> pfile->stats.time += group->fdinfo.data.time;
>>> @@ -3727,6 +3733,8 @@ int panthor_group_create(struct panthor_file *pfile,
>>>
>>> group_init_task_info(group);
>>>
>>> + xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);
>>> +
>>> return gid;
>>>
>>> err_erase_gid:
>>> @@ -3744,6 +3752,9 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
>>> struct panthor_scheduler *sched = ptdev->scheduler;
>>> struct panthor_group *group;
>>>
>>> + if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))
>>> + return -EINVAL;
>>> +
>>> group = xa_erase(&gpool->xa, group_handle);
>>> if (!group)
>>> return -EINVAL;
>>> @@ -3769,12 +3780,12 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
>>> }
>>>
>>> static struct panthor_group *group_from_handle(struct panthor_group_pool *pool,
>>> - u32 group_handle)
>>> + unsigned long group_handle)
>>> {
>>> struct panthor_group *group;
>>>
>>> xa_lock(&pool->xa);
>>> - group = group_get(xa_load(&pool->xa, group_handle));
>>> + group = group_get(xa_find(&pool->xa, &group_handle, group_handle, GROUP_REGISTERED));
>>> xa_unlock(&pool->xa);
>>>
>>> return group;
>>> @@ -3861,7 +3872,7 @@ panthor_fdinfo_gather_group_mem_info(struct panthor_file *pfile,
>>> return;
>>>
>>> xa_lock(&gpool->xa);
>>> - xa_for_each(&gpool->xa, i, group) {
>>> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
>>> stats->resident += group->fdinfo.kbo_sizes;
>>> if (group->csg_id >= 0)
>>> stats->active += group->fdinfo.kbo_sizes;
>>
>
On Thu, 27 Nov 2025 08:12:39 +0000
Akash Goel <akash.goel@arm.com> wrote:
> This commit prevents the possibility of a use after free issue in the
> GROUP_CREATE ioctl function, which arose as pointer to the group is
> accessed in that ioctl function after storing it in the Xarray.
> A malicious userspace can second guess the handle of a group and try
> to call GROUP_DESTROY ioctl from another thread around the same time
> as GROUP_CREATE ioctl.
>
> To prevent the use after free exploit, this commit uses a mark on an
> entry of group pool Xarray which is added just before returning from
> the GROUP_CREATE ioctl function. The mark is checked for all ioctls
> that specify the group handle and so userspace won't be abe to delete
> a group that isn't marked yet.
>
> Co-developed-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Akash Goel <akash.goel@arm.com>
Already approved privately, but here's the official
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
> ---
> drivers/gpu/drm/panthor/panthor_sched.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> index b834123a6560..a6b8024e1a3c 100644
> --- a/drivers/gpu/drm/panthor/panthor_sched.c
> +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> @@ -779,6 +779,12 @@ struct panthor_job_profiling_data {
> */
> #define MAX_GROUPS_PER_POOL 128
>
> +/*
> + * Mark added on an entry of group pool Xarray to identify if the group has
> + * been fully initialized and can be accessed elsewhere in the driver code.
> + */
> +#define GROUP_REGISTERED XA_MARK_1
> +
> /**
> * struct panthor_group_pool - Group pool
> *
> @@ -3007,7 +3013,7 @@ void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile)
> return;
>
> xa_lock(&gpool->xa);
> - xa_for_each(&gpool->xa, i, group) {
> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
> guard(spinlock)(&group->fdinfo.lock);
> pfile->stats.cycles += group->fdinfo.data.cycles;
> pfile->stats.time += group->fdinfo.data.time;
> @@ -3727,6 +3733,8 @@ int panthor_group_create(struct panthor_file *pfile,
>
> group_init_task_info(group);
>
> + xa_set_mark(&gpool->xa, gid, GROUP_REGISTERED);
> +
> return gid;
>
> err_erase_gid:
> @@ -3744,6 +3752,9 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
> struct panthor_scheduler *sched = ptdev->scheduler;
> struct panthor_group *group;
>
> + if (!xa_get_mark(&gpool->xa, group_handle, GROUP_REGISTERED))
> + return -EINVAL;
> +
> group = xa_erase(&gpool->xa, group_handle);
> if (!group)
> return -EINVAL;
> @@ -3769,12 +3780,12 @@ int panthor_group_destroy(struct panthor_file *pfile, u32 group_handle)
> }
>
> static struct panthor_group *group_from_handle(struct panthor_group_pool *pool,
> - u32 group_handle)
> + unsigned long group_handle)
> {
> struct panthor_group *group;
>
> xa_lock(&pool->xa);
> - group = group_get(xa_load(&pool->xa, group_handle));
> + group = group_get(xa_find(&pool->xa, &group_handle, group_handle, GROUP_REGISTERED));
> xa_unlock(&pool->xa);
>
> return group;
> @@ -3861,7 +3872,7 @@ panthor_fdinfo_gather_group_mem_info(struct panthor_file *pfile,
> return;
>
> xa_lock(&gpool->xa);
> - xa_for_each(&gpool->xa, i, group) {
> + xa_for_each_marked(&gpool->xa, i, group, GROUP_REGISTERED) {
> stats->resident += group->fdinfo.kbo_sizes;
> if (group->csg_id >= 0)
> stats->active += group->fdinfo.kbo_sizes;
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