[PATCH] device property: Don't overwrite addr when failing in device_get_mac_address

[PATCH] device property: Don't overwrite addr when failing in device_get_mac_address

[Julien Grall]

The function device_get_mac_address is trying different property names
in order to get the mac address. To check the return value, the variable
addr (which contain the buffer pass by the caller) will be re-used. This
means that if the previous property is not found, the next property will
be read using a NULL buffer.

Therefore it's only possible to retrieve the mac if node contains a
property "mac-address". Fix it by using a temporary buffer for the
return value.

This has been introduced by commit 4c96b7dc0d393f12c17e0d81db15aa4a820a6ab3
"Add a matching set of device_ functions for determining mac/phy"

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: David S. Miller <davem@davemloft.net>

---
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: netdev@vger.kernel.org
---
 drivers/base/property.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index ff03f23..2d75366 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -611,13 +611,15 @@ static void *device_get_mac_addr(struct device *dev,
 */
 void *device_get_mac_address(struct device *dev, char *addr, int alen)
 {
-	addr = device_get_mac_addr(dev, "mac-address", addr, alen);
-	if (addr)
-		return addr;
+	char *res;
 
-	addr = device_get_mac_addr(dev, "local-mac-address", addr, alen);
-	if (addr)
-		return addr;
+	res = device_get_mac_addr(dev, "mac-address", addr, alen);
+	if (res)
+		return res;
+
+	res = device_get_mac_addr(dev, "local-mac-address", addr, alen);
+	if (res)
+		return res;
 
 	return device_get_mac_addr(dev, "address", addr, alen);
 }
-- 
2.1.4

Re: [PATCH] device property: Don't overwrite addr when failing in device_get_mac_address

[Jeremy Linton]

On 09/03/2015 05:59 PM, Julien Grall wrote:
> The function device_get_mac_address is trying different property names
> in order to get the mac address. To check the return value, the variable
> addr (which contain the buffer pass by the caller) will be re-used. This
> means that if the previous property is not found, the next property will
> be read using a NULL buffer.

Thanks for catching that! I checked the OF version to see if it has the 
same problem, but of course it doesn't because I added the logic to pass 
the buffer into the routine.

Reviewed-by: Jeremy Linton <jeremy.linton@arm.com>

Re: [PATCH] device property: Don't overwrite addr when failing in device_get_mac_address

[David Miller]

From: Julien Grall <julien.grall@citrix.com>
Date: Thu, 3 Sep 2015 23:59:50 +0100

> The function device_get_mac_address is trying different property names
> in order to get the mac address. To check the return value, the variable
> addr (which contain the buffer pass by the caller) will be re-used. This
> means that if the previous property is not found, the next property will
> be read using a NULL buffer.
> 
> Therefore it's only possible to retrieve the mac if node contains a
> property "mac-address". Fix it by using a temporary buffer for the
> return value.
> 
> This has been introduced by commit 4c96b7dc0d393f12c17e0d81db15aa4a820a6ab3
> "Add a matching set of device_ functions for determining mac/phy"
> 
> Signed-off-by: Julien Grall <julien.grall@citrix.com>

Applied, thanks.