media: i2c: ccs: Check rules is non-NULL

Fix the following smatch warning:

drivers/media/i2c/ccs/ccs-data.c:524 ccs_data_parse_rules() warn: address
of NULL pointer 'rules'

The CCS static data rule parser does not check an if rule has been
obtained before checking for other rule types (which depend on the if
rule). In practice this means parsing invalid CCS static data could lead
to dereferencing a NULL pointer.
Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Fixes: a6b396f4 ("media: ccs: Add CCS static data parser library")
Cc: stable@vger.kernel.org # for 5.11 and up
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/i2c/ccs/ccs-data.c

@@ -464,8 +464,7 @@ static int ccs_data_parse_rules(struct bin_container *bin,
 		rule_payload = __rule_type + 1;
 		rule_plen2 = rule_plen - sizeof(*__rule_type);
 
-		switch (*__rule_type) {
-		case CCS_DATA_BLOCK_RULE_ID_IF: {
+		if (*__rule_type == CCS_DATA_BLOCK_RULE_ID_IF) {
 			const struct __ccs_data_block_rule_if *__if_rules =
 				rule_payload;
 			const size_t __num_if_rules =
@@ -514,49 +513,61 @@ static int ccs_data_parse_rules(struct bin_container *bin,
 				rules->if_rules = if_rule;
 				rules->num_if_rules = __num_if_rules;
 			}
-			break;
-		}
-		case CCS_DATA_BLOCK_RULE_ID_READ_ONLY_REGS:
-			rval = ccs_data_parse_reg_rules(bin, &rules->read_only_regs,
-							&rules->num_read_only_regs,
-							rule_payload,
-							rule_payload + rule_plen2,
-							dev);
-			if (rval)
-				return rval;
-			break;
-		case CCS_DATA_BLOCK_RULE_ID_FFD:
-			rval = ccs_data_parse_ffd(bin, &rules->frame_format,
-						  rule_payload,
-						  rule_payload + rule_plen2,
-						  dev);
-			if (rval)
-				return rval;
-			break;
-		case CCS_DATA_BLOCK_RULE_ID_MSR:
-			rval = ccs_data_parse_reg_rules(bin,
-							&rules->manufacturer_regs,
-							&rules->num_manufacturer_regs,
-							rule_payload,
-							rule_payload + rule_plen2,
-							dev);
-			if (rval)
-				return rval;
-			break;
-		case CCS_DATA_BLOCK_RULE_ID_PDAF_READOUT:
-			rval = ccs_data_parse_pdaf_readout(bin,
-							   &rules->pdaf_readout,
-							   rule_payload,
-							   rule_payload + rule_plen2,
-							   dev);
-			if (rval)
-				return rval;
-			break;
-		default:
-			dev_dbg(dev,
-				"Don't know how to handle rule type %u!\n",
-				*__rule_type);
-			return -EINVAL;
+		} else {
+			/* Check there was an if rule before any other rules */
+			if (bin->base && !rules)
+				return -EINVAL;
+
+			switch (*__rule_type) {
+			case CCS_DATA_BLOCK_RULE_ID_READ_ONLY_REGS:
+				rval = ccs_data_parse_reg_rules(bin,
+								rules ?
+								&rules->read_only_regs : NULL,
+								rules ?
+								&rules->num_read_only_regs : NULL,
+								rule_payload,
+								rule_payload + rule_plen2,
+								dev);
+				if (rval)
+					return rval;
+				break;
+			case CCS_DATA_BLOCK_RULE_ID_FFD:
+				rval = ccs_data_parse_ffd(bin, rules ?
+							  &rules->frame_format : NULL,
+							  rule_payload,
+							  rule_payload + rule_plen2,
+							  dev);
+				if (rval)
+					return rval;
+				break;
+			case CCS_DATA_BLOCK_RULE_ID_MSR:
+				rval = ccs_data_parse_reg_rules(bin,
+								rules ?
+								&rules->manufacturer_regs : NULL,
+								rules ?
+								&rules->num_manufacturer_regs : NULL,
+								rule_payload,
+								rule_payload + rule_plen2,
+								dev);
+				if (rval)
+					return rval;
+				break;
+			case CCS_DATA_BLOCK_RULE_ID_PDAF_READOUT:
+				rval = ccs_data_parse_pdaf_readout(bin,
+								   rules ?
+								   &rules->pdaf_readout : NULL,
+								   rule_payload,
+								   rule_payload + rule_plen2,
+								   dev);
+				if (rval)
+					return rval;
+				break;
+			default:
+				dev_dbg(dev,
+					"Don't know how to handle rule type %u!\n",
+					*__rule_type);
+				return -EINVAL;
+			}
 		}
 		__next_rule = __next_rule + rule_hlen + rule_plen;
 	}