[PATCH v2] drm/panthor: skip zero-sized firmware sections

[Osama Abdelkader <osama.abdelkader@gmail.com>]

panthor_fw_load_section_entry() skips BO creation when the firmware section
VA range is empty. If such a section is added to the firmware section list,
section->mem is left as NULL.

Later reload and unplug paths iterate over all firmware sections and
dereference section->mem, which can lead to a NULL pointer dereference.

Zero-sized firmware sections are valid, so accept them as no-op entries but
skip adding them to the section list.

Fixes: 2718d91816ee ("drm/panthor: Add the FW logical block")
Cc: stable@vger.kernel.org
Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
---
 drivers/gpu/drm/panthor/panthor_fw.c | 4 ++++
 1 file changed, 4 insertions(+)

v2:
- Accept zero-sized firmware sections as no-op entries instead of rejecting
  them, as suggested by Steven.

diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
index a338c4f0a7f5..66d9f5947af0 100644
--- a/drivers/gpu/drm/panthor/panthor_fw.c
+++ b/drivers/gpu/drm/panthor/panthor_fw.c
@@ -601,8 +601,11 @@ static int panthor_fw_load_section_entry(struct panthor_device *ptdev,
 	if (data_size > section_size) {
 		drm_err(&ptdev->base, "Firmware corrupted, section data exceeds section size\n");
 		return -EINVAL;
 	}
 
+	if (!section_size)
+		return 0;
+
 	name_len = iter->size - iter->offset;
 
 	section = drmm_kzalloc(&ptdev->base, sizeof(*section), GFP_KERNEL);
-- 
2.43.0