kernel: fix bugs added with mac-address-ascii support

1. Check for -EPROBE_DEFER
If it occurs we have to return immediately. Trying other properties
could result in another error and ignoring -EPROBE_DEFER which has a
special meaning.

2. Check for read result
Assuming property->read() success can result in NULL pointer
dereference. It happens e.g. for "mac-address" with NVMEM cell
containing invalid MAC.

3. Simplify code
Don't move cell reading & nvmem_cell_put() into a loop. Simplify loop
code.

Fixes: ecd81de7a5ab ("ath79: add nvmem cell mac-address-ascii support")
Cc: Yousong Zhou <[email protected]>
Signed-off-by: Rafał Miłecki <[email protected]>

target/linux/generic/hack-5.10/601-of_net-add-mac-address-ascii-support.patch

@@ -75,36 +75,35 @@ Submitted-by: Yousong Zhou <[email protected]>
  /**
   * Obtain the MAC address from an nvmem cell named 'mac-address' associated
   * with given device.
-@@ -552,19 +609,23 @@ int nvmem_get_mac_address(struct device
+@@ -550,21 +607,28 @@ EXPORT_SYMBOL(eth_platform_get_mac_addre
+  */
+ int nvmem_get_mac_address(struct device *dev, void *addrbuf)
  {
++	struct nvmem_cell_mac_address_property *property;
  	struct nvmem_cell *cell;
  	const void *mac;
 -	size_t len;
-+	struct nvmem_cell_mac_address_property *property;
 +	int i;
- 
--	cell = nvmem_cell_get(dev, "mac-address");
--	if (IS_ERR(cell))
--		return PTR_ERR(cell);
--
--	mac = nvmem_cell_read(cell, &len);
--	nvmem_cell_put(cell);
--
--	if (IS_ERR(mac))
--		return PTR_ERR(mac);
++
 +	for (i = 0; i < ARRAY_SIZE(nvmem_cell_mac_address_properties); i++) {
 +		property = &nvmem_cell_mac_address_properties[i];
 +		cell = nvmem_cell_get(dev, property->name);
-+		if (IS_ERR(cell)) {
-+			if (i == ARRAY_SIZE(nvmem_cell_mac_address_properties) - 1)
-+				return PTR_ERR(cell);
-+			continue;
-+		}
-+		mac = property->read(cell);
-+		nvmem_cell_put(cell);
-+		break;
++		/* For -EPROBE_DEFER don't try other properties. We'll get back to this one. */
++		if (!IS_ERR(cell) || PTR_ERR(cell) == -EPROBE_DEFER)
++			break;
 +	}
  
+-	cell = nvmem_cell_get(dev, "mac-address");
+ 	if (IS_ERR(cell))
+ 		return PTR_ERR(cell);
+ 
+-	mac = nvmem_cell_read(cell, &len);
++	mac = property->read(cell);
+ 	nvmem_cell_put(cell);
+-
+ 	if (IS_ERR(mac))
+ 		return PTR_ERR(mac);
+ 
 -	if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
 +	if (!is_valid_ether_addr(mac)) {
  		kfree(mac);

target/linux/generic/hack-5.15/601-of_net-add-mac-address-ascii-support.patch

@@ -75,36 +75,35 @@ Submitted-by: Yousong Zhou <[email protected]>
  /**
   * nvmem_get_mac_address - Obtain the MAC address from an nvmem cell named
   * 'mac-address' associated with given device.
-@@ -551,19 +608,23 @@ int nvmem_get_mac_address(struct device
+@@ -549,21 +606,28 @@ EXPORT_SYMBOL(eth_platform_get_mac_addre
+  */
+ int nvmem_get_mac_address(struct device *dev, void *addrbuf)
  {
++	struct nvmem_cell_mac_address_property *property;
  	struct nvmem_cell *cell;
  	const void *mac;
 -	size_t len;
-+	struct nvmem_cell_mac_address_property *property;
 +	int i;
- 
--	cell = nvmem_cell_get(dev, "mac-address");
--	if (IS_ERR(cell))
--		return PTR_ERR(cell);
--
--	mac = nvmem_cell_read(cell, &len);
--	nvmem_cell_put(cell);
--
--	if (IS_ERR(mac))
--		return PTR_ERR(mac);
++
 +	for (i = 0; i < ARRAY_SIZE(nvmem_cell_mac_address_properties); i++) {
 +		property = &nvmem_cell_mac_address_properties[i];
 +		cell = nvmem_cell_get(dev, property->name);
-+		if (IS_ERR(cell)) {
-+			if (i == ARRAY_SIZE(nvmem_cell_mac_address_properties) - 1)
-+				return PTR_ERR(cell);
-+			continue;
-+		}
-+		mac = property->read(cell);
-+		nvmem_cell_put(cell);
-+		break;
++		/* For -EPROBE_DEFER don't try other properties. We'll get back to this one. */
++		if (!IS_ERR(cell) || PTR_ERR(cell) == -EPROBE_DEFER)
++			break;
 +	}
  
+-	cell = nvmem_cell_get(dev, "mac-address");
+ 	if (IS_ERR(cell))
+ 		return PTR_ERR(cell);
+ 
+-	mac = nvmem_cell_read(cell, &len);
++	mac = property->read(cell);
+ 	nvmem_cell_put(cell);
+-
+ 	if (IS_ERR(mac))
+ 		return PTR_ERR(mac);
+ 
 -	if (len != ETH_ALEN || !is_valid_ether_addr(mac)) {
 +	if (!is_valid_ether_addr(mac)) {
  		kfree(mac);