Re: [Patch net v2] net: check dev->addr_len for dev_set_mac_address()

[David Miller]

From: Cong Wang 
Date: Wed, 26 Jul 2017 15:22:06 -0700

> Historically, dev_ifsioc() uses struct sockaddr as mac
> address definition, this is why dev_set_mac_address()
> accepts a struct sockaddr pointer as input but now we
> have various types of mac addresse whose lengths
> are up to MAX_ADDR_LEN, longer than struct sockaddr,
> and saved in dev->addr_len.
> 
> It is too late to fix dev_ifsioc() due to API
> compatibility, so just reject those larger than
> sizeof(struct sockaddr), otherwise we would read
> and use some random bytes from kernel stack.
> 
> Fortunately, only a few IPv6 tunnel devices have addr_len
> larger than sizeof(struct sockaddr) and they don't support
> ndo_set_mac_addr(). But with team driver, in lb mode, they
> can still be enslaved to a team master and make its mac addr
> length as the same.
> 
> Cc: Jiri Pirko 
> Signed-off-by: Cong Wang 

Applied.

[Patch net v2] net: check dev->addr_len for dev_set_mac_address()

[Cong Wang]

Historically, dev_ifsioc() uses struct sockaddr as mac
address definition, this is why dev_set_mac_address()
accepts a struct sockaddr pointer as input but now we
have various types of mac addresse whose lengths
are up to MAX_ADDR_LEN, longer than struct sockaddr,
and saved in dev->addr_len.

It is too late to fix dev_ifsioc() due to API
compatibility, so just reject those larger than
sizeof(struct sockaddr), otherwise we would read
and use some random bytes from kernel stack.

Fortunately, only a few IPv6 tunnel devices have addr_len
larger than sizeof(struct sockaddr) and they don't support
ndo_set_mac_addr(). But with team driver, in lb mode, they
can still be enslaved to a team master and make its mac addr
length as the same.

Cc: Jiri Pirko 
Signed-off-by: Cong Wang 
---
 net/core/dev_ioctl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 06b147d7d9e2..709a4e6fb447 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -263,6 +263,8 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, 
unsigned int cmd)
return dev_set_mtu(dev, ifr->ifr_mtu);
 
case SIOCSIFHWADDR:
+   if (dev->addr_len > sizeof(struct sockaddr))
+   return -EINVAL;
return dev_set_mac_address(dev, >ifr_hwaddr);
 
case SIOCSIFHWBROADCAST:
-- 
2.13.0