[PATCH] drm/panthor: reject firmware sections with oversized data

[Osama Abdelkader]

In panthor_fw_load_section_entry(), the data size to copy is calculated
without validating it against the allocated section_size:

    section->data.size = hdr.data.end - hdr.data.start;

If a crafted firmware sets data.size larger than the allocated memory,
this could cause a heap buffer overflow in panthor_fw_init_section_mem()

    memcpy(section->mem->kmap, section->data.buf, section->data.size);

Additionally, if the section->data.size exceeds the BO size, could this
memset underflow the size calculation, leading to a massive out-of-bounds
zeroing of kernel memory?

    memset(section->mem->kmap + section->data.size, 0,
           panthor_kernel_bo_size(section->mem) - section->data.size);

Reject section entries whose initial data is larger than the section size.

Fixes: 2718d91816ee ("drm/panthor: Add the FW logical block")
Cc: sta...@vger.kernel.org
Signed-off-by: Osama Abdelkader <osama.abdelka...@gmail.com>
---
 drivers/gpu/drm/panthor/panthor_fw.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_fw.c 
b/drivers/gpu/drm/panthor/panthor_fw.c
index 986151681b24..a338c4f0a7f5 100644
--- a/drivers/gpu/drm/panthor/panthor_fw.c
+++ b/drivers/gpu/drm/panthor/panthor_fw.c
@@ -545,6 +545,7 @@ static int panthor_fw_load_section_entry(struct 
panthor_device *ptdev,
        struct panthor_fw_binary_section_entry_hdr hdr;
        struct panthor_fw_section *section;
        u32 section_size;
+       u32 data_size;
        u32 name_len;
        int ret;
 
@@ -595,6 +596,13 @@ static int panthor_fw_load_section_entry(struct 
panthor_device *ptdev,
                return -EINVAL;
        }
 
+       section_size = hdr.va.end - hdr.va.start;
+       data_size = hdr.data.end - hdr.data.start;
+       if (data_size > section_size) {
+               drm_err(&ptdev->base, "Firmware corrupted, section data exceeds 
section size\n");
+               return -EINVAL;
+       }
+
        name_len = iter->size - iter->offset;
 
        section = drmm_kzalloc(&ptdev->base, sizeof(*section), GFP_KERNEL);
@@ -603,7 +611,7 @@ static int panthor_fw_load_section_entry(struct 
panthor_device *ptdev,
 
        list_add_tail(&section->node, &ptdev->fw->sections);
        section->flags = hdr.flags;
-       section->data.size = hdr.data.end - hdr.data.start;
+       section->data.size = data_size;
 
        if (section->data.size > 0) {
                void *data = drmm_kmalloc(&ptdev->base, section->data.size, 
GFP_KERNEL);
@@ -626,7 +634,6 @@ static int panthor_fw_load_section_entry(struct 
panthor_device *ptdev,
                section->name = name;
        }
 
-       section_size = hdr.va.end - hdr.va.start;
        if (section_size) {
                u32 cache_mode = hdr.flags & 
CSF_FW_BINARY_IFACE_ENTRY_CACHE_MODE_MASK;
                struct panthor_gem_object *bo;
-- 
2.43.0