Re: [PATCH v3] drm/panthor: Fix couple of NULL vs IS_ERR() bugs

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Hi Boris,

On 03/04/24 12:47, Boris Brezillon wrote:
On Tue,  2 Apr 2024 07:14:11 -0700
Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx> wrote:

Currently panthor_vm_get_heap_pool() returns both ERR_PTR() and
NULL(when create is false and if there is no poool attached to the
VM)
	- Change the function to return error pointers, when pool is
	  NULL return -ENOENT
	- Also handle the callers to check for IS_ERR() on failure.

Fixes: 4bdca1150792 ("drm/panthor: Add the driver frontend block")
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>

Queued to drm-misc-next with the following commit message:

"
drm/panthor: Don't return NULL from panthor_vm_get_heap_pool()
The kernel doc says this function returns either a valid pointer
or an ERR_PTR(), but in practice this function can return NULL if
create=false. Fix the function to match the doc (return
ERR_PTR(-ENOENT) instead of NULL) and adjust all call-sites
accordingly.
"


Thanks a lot for making the change!

Regards,
Harshit

Thanks,

Boris

---
This is spotted by smatch and the patch is only compile tested

v1->v2: Fix the function panthor_vm_get_heap_pool() to only return error
pointers and handle the caller sites [Suggested by Boris Brezillon]
         - Also merge these IS_ERR() vs NULL bugs into same patch

v2->v3: pull out error checking for devm_drm_dev_alloc() failure.
---
  drivers/gpu/drm/panthor/panthor_drv.c   | 4 ++--
  drivers/gpu/drm/panthor/panthor_mmu.c   | 2 ++
  drivers/gpu/drm/panthor/panthor_sched.c | 2 +-
  3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index 11b3ccd58f85..050b905b0453 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1090,8 +1090,8 @@ static int panthor_ioctl_tiler_heap_destroy(struct drm_device *ddev, void *data,
  		return -EINVAL;
pool = panthor_vm_get_heap_pool(vm, false);
-	if (!pool) {
-		ret = -EINVAL;
+	if (IS_ERR(pool)) {
+		ret = PTR_ERR(pool);
  		goto out_put_vm;
  	}
diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index fdd35249169f..e1285cdb09ff 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -1893,6 +1893,8 @@ struct panthor_heap_pool *panthor_vm_get_heap_pool(struct panthor_vm *vm, bool c
  			vm->heaps.pool = panthor_heap_pool_get(pool);
  	} else {
  		pool = panthor_heap_pool_get(vm->heaps.pool);
+		if (!pool)
+			pool = ERR_PTR(-ENOENT);
  	}
  	mutex_unlock(&vm->heaps.lock);
diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
index 5f7803b6fc48..617df2b980d0 100644
--- a/drivers/gpu/drm/panthor/panthor_sched.c
+++ b/drivers/gpu/drm/panthor/panthor_sched.c
@@ -1343,7 +1343,7 @@ static int group_process_tiler_oom(struct panthor_group *group, u32 cs_id)
  	if (unlikely(csg_id < 0))
  		return 0;
- if (!heaps || frag_end > vt_end || vt_end >= vt_start) {
+	if (IS_ERR(heaps) || frag_end > vt_end || vt_end >= vt_start) {
  		ret = -EINVAL;
  	} else {
  		/* We do the allocation without holding the scheduler lock to avoid





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