[PATCH v2] drm/amdgpu/discovery: validate table offset before IP discovery header cast

[Pavitra Jha <jhapavitra98@gmail.com>]

Sashiko AI review of the previous fix flagged three remaining gaps in
the discovery blob parser, all stemming from the same root cause: the
ip_discovery_header pointer itself is constructed from a firmware-
controlled offset with no validation before the cast.

  ihdr = (struct ip_discovery_header *)(discovery_bin +
                    le16_to_cpu(bhdr->table_list[IP_DISCOVERY].offset));

This offset is a firmware-controlled u16 read directly from the
discovery blob's table_list, with no bounds check against
adev->discovery.size before being used to construct ihdr. Every
subsequent read from ihdr, including num_dies and die_info[], is
downstream of this unchecked pointer.

The other two items in that review (unbounded ip_offset advancement
via num_base_address, and num_dies exceeding die_info[]'s capacity)
were already addressed in the previous fix.

Fix by validating the table offset in amdgpu_discovery_get_table_info(),
which is the common path used by all callers except
amdgpu_discovery_read_harvest_bit_per_ip() (which reads
table_list[IP_DISCOVERY].offset directly rather than going through
get_table_info()). Add the equivalent check at that direct access site
as well, so all paths that construct an ip_discovery_header pointer
from a table offset are covered.

The check validates the offset itself against adev->discovery.size,
independent of any specific downstream struct size, since
get_table_info() is shared across ten different table types
(IP_DISCOVERY, HARVEST_INFO, GC, MALL_INFO, VCN_INFO, NPS_INFO, and
others) each with differently-sized table structures.

Fixes: d0c647a6aae2 ("drm/amdgpu/discovery: support new discovery binary header")
Cc: stable@vger.kernel.org
Signed-off-by: Pavitra Jha <jhapavitra98@gmail.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
index b4ee5fc8e..9b55c56cb 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
@@ -564,6 +564,12 @@ static int amdgpu_discovery_get_table_info(struct amdgpu_device *adev,
 		return -EINVAL;
 	}
 
+	if (le16_to_cpu((*info)->offset) >= adev->discovery.size) {
+		dev_err(adev->dev, "invalid table offset %u for table_id %u\n",
+			le16_to_cpu((*info)->offset), table_id);
+		return -EINVAL;
+	}
+
 	return 0;
 }
 
@@ -766,6 +772,14 @@ static void amdgpu_discovery_read_harvest_bit_per_ip(struct amdgpu_device *adev,
 	int i, j;
 
 	bhdr = (struct binary_header *)discovery_bin;
+
+	if (le16_to_cpu(bhdr->table_list[IP_DISCOVERY].offset) >=
+	    adev->discovery.size) {
+		dev_err(adev->dev, "invalid IP_DISCOVERY table offset %u\n",
+			le16_to_cpu(bhdr->table_list[IP_DISCOVERY].offset));
+		return;
+	}
+
 	ihdr = (struct ip_discovery_header
 			*)(discovery_bin +
 			   le16_to_cpu(bhdr->table_list[IP_DISCOVERY].offset));
-- 
2.53.0