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rtnetlink: NUL-terminate IFLA_PHYS_PORT_NAME string

PATCH In review Michal Schmidt 3 participants 3 messages May 4, 2017

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Michal Schmidt

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#0 lore raw

PATCH 1/1 rtnetlink: NUL-terminate IFLA_PHYS_PORT_NAME string

IFLA_PHYS_PORT_NAME is a string attribute, so terminate it with \0. Otherwise libnl3 fails to validate netlink messages with this attribute. "ip -detail a" assumes too that the attribute is NUL-terminated when printing it. It often was, due to padding.

I noticed this as libvirtd failing to start on a system with sfc driver after upgrading it to Linux 4.11, i.e. when sfc added support for phys_port_name.

Signed-off-by Michal Schmidt <[email protected]>
---
 net/core/rtnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
net/core/rtnetlink.c +1 -1
index c4e84c5582..69daf393cb 100644
@@ -1056,7 +1056,7 @@ static int rtnl_phys_port_name_fill(struct sk_buff *skb, struct net_device *dev)
 		return err;
 	}
 
-	if (nla_put(skb, IFLA_PHYS_PORT_NAME, strlen(name), name))
+	if (nla_put_string(skb, IFLA_PHYS_PORT_NAME, name))
 		return -EMSGSIZE;
 
 	return 0;
Signature · 1 line
2.12.2
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#1 lore raw

From: Michal Schmidt <[email protected]>
Date: Thu, 4 May 2017 16:48:58 +0200

Quoted 10 lines

IFLA_PHYS_PORT_NAME is a string attribute, so terminate it with \0. Otherwise libnl3 fails to validate netlink messages with this attribute. "ip -detail a" assumes too that the attribute is NUL-terminated when printing it. It often was, due to padding.

I noticed this as libvirtd failing to start on a system with sfc driver after upgrading it to Linux 4.11, i.e. when sfc added support for phys_port_name.

Signed-off-by Michal Schmidt <[email protected]>

Good catch, applied and queued up for -stable, thanks.

#2 lore raw
In reply to Michal Schmidt
Quoted 20 lines · Michal Schmidt

IFLA_PHYS_PORT_NAME is a string attribute, so terminate it with \0. Otherwise libnl3 fails to validate netlink messages with this attribute. "ip -detail a" assumes too that the attribute is NUL-terminated when printing it. It often was, due to padding.

I noticed this as libvirtd failing to start on a system with sfc driver after upgrading it to Linux 4.11, i.e. when sfc added support for phys_port_name.

Signed-off-by Michal Schmidt <[email protected]>
---
 net/core/rtnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
net/core/rtnetlink.c +0 -0
index c4e84c5582..69daf393cb 100644

net/core/rtnetlink.c static int rtnl_phys_port_name_fill(struct sk_buff *skb, struct net_device *dev) · line 1062

Quoted 8 lines
net/core/rtnetlink.c +1 -1
@@ -1056,7 +1056,7 @@ static int rtnl_phys_port_name_fill(struct sk_buff *skb, struct net_device *dev)
 		return err;
 	}
 
-	if (nla_put(skb, IFLA_PHYS_PORT_NAME, strlen(name), name))
+	if (nla_put_string(skb, IFLA_PHYS_PORT_NAME, name))
 		return -EMSGSIZE;
 
 	return 0;

Thanks for fixing.