[PATCH] drm/amdkfd: Fix out-of-bounds read in kdf_create_vcrat_image_cpu()

[Jeremy Cline]

KASAN reported a slab-out-of-bounds read of size 1 in
kdf_create_vcrat_image_cpu().

This occurs when, for example, when on an x86_64 with a single NUMA node
because kfd_fill_iolink_info_for_cpu() is a no-op, but afterwards the
sub_type_hdr->length, which is out-of-bounds, is read and multiplied by
entries. Fortunately, entries is 0 in this case so the overall
crat_table->length is still correct.

This refactors the helper functions to accept the crat_table directly
and calculate the table entry pointer based on the current table length.
This allows us to avoid an out-of-bounds read and hopefully makes the
pointer arithmetic clearer. It should have no functional change beyond
removing the out-of-bounds read.

Fixes: b7b6c38529c9 ("drm/amdkfd: Calculate CPU VCRAT size dynamically (v2)")
Signed-off-by: Jeremy Cline <jcline@xxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdkfd/kfd_crat.c | 86 +++++++++++++--------------
 1 file changed, 40 insertions(+), 46 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
index 8cac497c2c45..e50db2c0f4ee 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
@@ -829,21 +829,24 @@ int kfd_create_crat_image_acpi(void **crat_image, size_t *size)
 /* kfd_fill_cu_for_cpu - Fill in Compute info for the given CPU NUMA node
  *
  *	@numa_node_id: CPU NUMA node id
- *	@avail_size: Available size in the memory
- *	@sub_type_hdr: Memory into which compute info will be filled in
+ *	@avail_size: Available space in bytes at the end of the @crat_table.
+ *	@crat_table: The CRAT table to append the Compute info to;
+ *		on success the table length and total_entries count is updated.
  *
  *	Return 0 if successful else return -ve value
  */
 static int kfd_fill_cu_for_cpu(int numa_node_id, int *avail_size,
-				int proximity_domain,
-				struct crat_subtype_computeunit *sub_type_hdr)
+				struct crat_header *crat_table)
 {
 	const struct cpumask *cpumask;
+	struct crat_subtype_computeunit *sub_type_hdr;
 
 	*avail_size -= sizeof(struct crat_subtype_computeunit);
 	if (*avail_size < 0)
 		return -ENOMEM;
 
+	sub_type_hdr = (typeof(sub_type_hdr))((char *)crat_table +
+		crat_table->length);
 	memset(sub_type_hdr, 0, sizeof(struct crat_subtype_computeunit));
 
 	/* Fill in subtype header data */
@@ -855,36 +858,42 @@ static int kfd_fill_cu_for_cpu(int numa_node_id, int *avail_size,
 
 	/* Fill in CU data */
 	sub_type_hdr->flags |= CRAT_CU_FLAGS_CPU_PRESENT;
-	sub_type_hdr->proximity_domain = proximity_domain;
+	sub_type_hdr->proximity_domain = crat_table->num_domains;
 	sub_type_hdr->processor_id_low = kfd_numa_node_to_apic_id(numa_node_id);
 	if (sub_type_hdr->processor_id_low == -1)
 		return -EINVAL;
 
 	sub_type_hdr->num_cpu_cores = cpumask_weight(cpumask);
 
+	crat_table->length += sub_type_hdr->length;
+	crat_table->total_entries++;
+
 	return 0;
 }
 
 /* kfd_fill_mem_info_for_cpu - Fill in Memory info for the given CPU NUMA node
  *
  *	@numa_node_id: CPU NUMA node id
- *	@avail_size: Available size in the memory
- *	@sub_type_hdr: Memory into which compute info will be filled in
+ *	@avail_size: Available space in bytes at the end of the @crat_table.
+ *	@crat_table: The CRAT table to append the Memory info to;
+ *		on success the table length and total_entries count is updated.
  *
  *	Return 0 if successful else return -ve value
  */
 static int kfd_fill_mem_info_for_cpu(int numa_node_id, int *avail_size,
-			int proximity_domain,
-			struct crat_subtype_memory *sub_type_hdr)
+			struct crat_header *crat_table)
 {
 	uint64_t mem_in_bytes = 0;
 	pg_data_t *pgdat;
 	int zone_type;
+	struct crat_subtype_memory *sub_type_hdr;
 
 	*avail_size -= sizeof(struct crat_subtype_memory);
 	if (*avail_size < 0)
 		return -ENOMEM;
 
+	sub_type_hdr = (typeof(sub_type_hdr))((char *)crat_table +
+		crat_table->length);
 	memset(sub_type_hdr, 0, sizeof(struct crat_subtype_memory));
 
 	/* Fill in subtype header data */
@@ -905,27 +914,37 @@ static int kfd_fill_mem_info_for_cpu(int numa_node_id, int *avail_size,
 
 	sub_type_hdr->length_low = lower_32_bits(mem_in_bytes);
 	sub_type_hdr->length_high = upper_32_bits(mem_in_bytes);
-	sub_type_hdr->proximity_domain = proximity_domain;
+	sub_type_hdr->proximity_domain = crat_table->num_domains;
+
+	crat_table->length += sub_type_hdr->length;
+	crat_table->total_entries++;
 
 	return 0;
 }
 
 #ifdef CONFIG_X86_64
+/* kfd_fill_iolink_info_for_cpu() - Add IO link info to a Virtual CRAT
+ *
+ * @numa_node_id: The NUMA node ID for the CPU; as from for_each_online_node()
+ * @avail_size: Available space in bytes at the end of the @crat_table.
+ * @crat_table: The CRAT table to append the IO link info to; on success the
+ *              table length and total_entries count is updated.
+ *
+ * Return: 0 if successful else return -ve value
+ */
 static int kfd_fill_iolink_info_for_cpu(int numa_node_id, int *avail_size,
-				uint32_t *num_entries,
-				struct crat_subtype_iolink *sub_type_hdr)
+				struct crat_header *crat_table)
 {
 	int nid;
 	struct cpuinfo_x86 *c = &cpu_data(0);
 	uint8_t link_type;
+	struct crat_subtype_iolink *sub_type_hdr;
 
 	if (c->x86_vendor == X86_VENDOR_AMD)
 		link_type = CRAT_IOLINK_TYPE_HYPERTRANSPORT;
 	else
 		link_type = CRAT_IOLINK_TYPE_QPI_1_1;
 
-	*num_entries = 0;
-
 	/* Create IO links from this node to other CPU nodes */
 	for_each_online_node(nid) {
 		if (nid == numa_node_id) /* node itself */
@@ -935,6 +954,8 @@ static int kfd_fill_iolink_info_for_cpu(int numa_node_id, int *avail_size,
 		if (*avail_size < 0)
 			return -ENOMEM;
 
+		sub_type_hdr = (typeof(sub_type_hdr))((char *)crat_table +
+			crat_table->length);
 		memset(sub_type_hdr, 0, sizeof(struct crat_subtype_iolink));
 
 		/* Fill in subtype header data */
@@ -947,8 +968,8 @@ static int kfd_fill_iolink_info_for_cpu(int numa_node_id, int *avail_size,
 		sub_type_hdr->proximity_domain_to = nid;
 		sub_type_hdr->io_interface_type = link_type;
 
-		(*num_entries)++;
-		sub_type_hdr++;
+		crat_table->length += sub_type_hdr->length;
+		crat_table->total_entries++;
 	}
 
 	return 0;
@@ -966,12 +987,8 @@ static int kfd_create_vcrat_image_cpu(void *pcrat_image, size_t *size)
 	struct crat_header *crat_table = (struct crat_header *)pcrat_image;
 	struct acpi_table_header *acpi_table;
 	acpi_status status;
-	struct crat_subtype_generic *sub_type_hdr;
 	int avail_size = *size;
 	int numa_node_id;
-#ifdef CONFIG_X86_64
-	uint32_t entries = 0;
-#endif
 	int ret = 0;
 
 	if (!pcrat_image)
@@ -1003,48 +1020,25 @@ static int kfd_create_vcrat_image_cpu(void *pcrat_image, size_t *size)
 	crat_table->total_entries = 0;
 	crat_table->num_domains = 0;
 
-	sub_type_hdr = (struct crat_subtype_generic *)(crat_table+1);
-
 	for_each_online_node(numa_node_id) {
 		if (kfd_numa_node_to_apic_id(numa_node_id) == -1)
 			continue;
 
 		/* Fill in Subtype: Compute Unit */
-		ret = kfd_fill_cu_for_cpu(numa_node_id, &avail_size,
-			crat_table->num_domains,
-			(struct crat_subtype_computeunit *)sub_type_hdr);
+		ret = kfd_fill_cu_for_cpu(numa_node_id, &avail_size, crat_table);
 		if (ret < 0)
 			return ret;
-		crat_table->length += sub_type_hdr->length;
-		crat_table->total_entries++;
-
-		sub_type_hdr = (typeof(sub_type_hdr))((char *)sub_type_hdr +
-			sub_type_hdr->length);
 
 		/* Fill in Subtype: Memory */
-		ret = kfd_fill_mem_info_for_cpu(numa_node_id, &avail_size,
-			crat_table->num_domains,
-			(struct crat_subtype_memory *)sub_type_hdr);
+		ret = kfd_fill_mem_info_for_cpu(numa_node_id, &avail_size, crat_table);
 		if (ret < 0)
 			return ret;
-		crat_table->length += sub_type_hdr->length;
-		crat_table->total_entries++;
-
-		sub_type_hdr = (typeof(sub_type_hdr))((char *)sub_type_hdr +
-			sub_type_hdr->length);
 
 		/* Fill in Subtype: IO Link */
 #ifdef CONFIG_X86_64
-		ret = kfd_fill_iolink_info_for_cpu(numa_node_id, &avail_size,
-				&entries,
-				(struct crat_subtype_iolink *)sub_type_hdr);
+		ret = kfd_fill_iolink_info_for_cpu(numa_node_id, &avail_size, crat_table);
 		if (ret < 0)
 			return ret;
-		crat_table->length += (sub_type_hdr->length * entries);
-		crat_table->total_entries += entries;
-
-		sub_type_hdr = (typeof(sub_type_hdr))((char *)sub_type_hdr +
-				sub_type_hdr->length * entries);
 #else
 		pr_info("IO link not available for non x86 platforms\n");
 #endif
-- 
2.28.0