rtnetlink: do_setlink: Use true struct sockaddr

[PATCH] rtnetlink: do_setlink: Use true struct sockaddr

Posted by Kees Cook 1 year ago

Instead of a heap allocation use a stack allocated struct sockaddr, as
dev_set_mac_address_user() is the consumer (which uses a classic
struct sockaddr). Cap the copy to the minimum address size between
the incoming address and the traditional sa_data field itself.

Putting "sa" on the stack means it will get a reused stack slot since
it is smaller than other existing single-scope stack variables (like
the vfinfo array).

Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Ido Schimmel <idosch@nvidia.com>
Cc: Petr Machata <petrm@nvidia.com>
Cc: netdev@vger.kernel.org
---
 net/core/rtnetlink.c | 22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index ab5f201bf0ab..6da0edc0870d 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -3048,21 +3048,13 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
 	}
 
 	if (tb[IFLA_ADDRESS]) {
-		struct sockaddr *sa;
-		int len;
-
-		len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
-						  sizeof(*sa));
-		sa = kmalloc(len, GFP_KERNEL);
-		if (!sa) {
-			err = -ENOMEM;
-			goto errout;
-		}
-		sa->sa_family = dev->type;
-		memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
-		       dev->addr_len);
-		err = dev_set_mac_address_user(dev, sa, extack);
-		kfree(sa);
+		struct sockaddr sa = { };
+
+		/* dev_set_mac_address_user() uses a true struct sockaddr. */
+		sa.sa_family = dev->type;
+		memcpy(sa.sa_data, nla_data(tb[IFLA_ADDRESS]),
+		       min(dev->addr_len, sizeof(sa.sa_data_min)));
+		err = dev_set_mac_address_user(dev, &sa, extack);
 		if (err)
 			goto errout;
 		status |= DO_SETLINK_MODIFIED;
-- 
2.34.1

Re: [PATCH] rtnetlink: do_setlink: Use true struct sockaddr

Posted by ericnetdev dumazet 1 year ago

Le mar. 17 déc. 2024 à 03:05, Kees Cook <kees@kernel.org> a écrit :
>
> Instead of a heap allocation use a stack allocated struct sockaddr, as
> dev_set_mac_address_user() is the consumer (which uses a classic
> struct sockaddr). Cap the copy to the minimum address size between
> the incoming address and the traditional sa_data field itself.

Not sure what is a 'classic sockaddr'

>
> Putting "sa" on the stack means it will get a reused stack slot since
> it is smaller than other existing single-scope stack variables (like
> the vfinfo array).
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Ido Schimmel <idosch@nvidia.com>
> Cc: Petr Machata <petrm@nvidia.com>
> Cc: netdev@vger.kernel.org
> ---
>  net/core/rtnetlink.c | 22 +++++++---------------
>  1 file changed, 7 insertions(+), 15 deletions(-)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index ab5f201bf0ab..6da0edc0870d 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -3048,21 +3048,13 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
>         }
>
>         if (tb[IFLA_ADDRESS]) {
> -               struct sockaddr *sa;
> -               int len;
> -
> -               len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
> -                                                 sizeof(*sa));
> -               sa = kmalloc(len, GFP_KERNEL);
> -               if (!sa) {
> -                       err = -ENOMEM;
> -                       goto errout;
> -               }
> -               sa->sa_family = dev->type;
> -               memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
> -                      dev->addr_len);
> -               err = dev_set_mac_address_user(dev, sa, extack);
> -               kfree(sa);
> +               struct sockaddr sa = { };
> +
> +               /* dev_set_mac_address_user() uses a true struct sockaddr. */
> +               sa.sa_family = dev->type;
> +               memcpy(sa.sa_data, nla_data(tb[IFLA_ADDRESS]),
> +                      min(dev->addr_len, sizeof(sa.sa_data_min)));
> +               err = dev_set_mac_address_user(dev, &sa, extack);

Have you added debug checks in dev_set_mac_address_user() to make sure
dev->addr_len is always smaller than 14 ?

I think we support devices with bigger addresses.

Re: [PATCH] rtnetlink: do_setlink: Use true struct sockaddr

Posted by Kuniyuki Iwashima 1 year ago

From: Kees Cook <kees@kernel.org>
Date: Mon, 16 Dec 2024 18:04:45 -0800
> Instead of a heap allocation use a stack allocated struct sockaddr, as
> dev_set_mac_address_user() is the consumer (which uses a classic
> struct sockaddr).

I remember Eric's feedback was to keep using heap instead of stack
because rtnl_newlink() path already uses too much on stack.


> Cap the copy to the minimum address size between
> the incoming address and the traditional sa_data field itself.
> 
> Putting "sa" on the stack means it will get a reused stack slot since
> it is smaller than other existing single-scope stack variables (like
> the vfinfo array).
> 
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Ido Schimmel <idosch@nvidia.com>
> Cc: Petr Machata <petrm@nvidia.com>
> Cc: netdev@vger.kernel.org
> ---
>  net/core/rtnetlink.c | 22 +++++++---------------
>  1 file changed, 7 insertions(+), 15 deletions(-)
> 
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index ab5f201bf0ab..6da0edc0870d 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -3048,21 +3048,13 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
>  	}
>  
>  	if (tb[IFLA_ADDRESS]) {
> -		struct sockaddr *sa;
> -		int len;
> -
> -		len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
> -						  sizeof(*sa));
> -		sa = kmalloc(len, GFP_KERNEL);
> -		if (!sa) {
> -			err = -ENOMEM;
> -			goto errout;
> -		}
> -		sa->sa_family = dev->type;
> -		memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
> -		       dev->addr_len);
> -		err = dev_set_mac_address_user(dev, sa, extack);
> -		kfree(sa);
> +		struct sockaddr sa = { };
> +
> +		/* dev_set_mac_address_user() uses a true struct sockaddr. */
> +		sa.sa_family = dev->type;
> +		memcpy(sa.sa_data, nla_data(tb[IFLA_ADDRESS]),
> +		       min(dev->addr_len, sizeof(sa.sa_data_min)));
> +		err = dev_set_mac_address_user(dev, &sa, extack);
>  		if (err)
>  			goto errout;
>  		status |= DO_SETLINK_MODIFIED;
> -- 
> 2.34.1

Re: [PATCH] rtnetlink: do_setlink: Use true struct sockaddr

Posted by Kees Cook 1 year ago


On December 16, 2024 6:41:56 PM PST, Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>From: Kees Cook <kees@kernel.org>
>Date: Mon, 16 Dec 2024 18:04:45 -0800
>> Instead of a heap allocation use a stack allocated struct sockaddr, as
>> dev_set_mac_address_user() is the consumer (which uses a classic
>> struct sockaddr).
>
>I remember Eric's feedback was to keep using heap instead of stack
>because rtnl_newlink() path already uses too much on stack.

See below...

>
>
>> Cap the copy to the minimum address size between
>> the incoming address and the traditional sa_data field itself.
>> 
>> Putting "sa" on the stack means it will get a reused stack slot since
>> it is smaller than other existing single-scope stack variables (like
>> the vfinfo array).

That's why I included the rationale above. (I.e. stack usage does not grow with this patch.)

-Kees

>> 
>> Signed-off-by: Kees Cook <kees@kernel.org>
>> ---
>> Cc: Eric Dumazet <edumazet@google.com>
>> Cc: "David S. Miller" <davem@davemloft.net>
>> Cc: Jakub Kicinski <kuba@kernel.org>
>> Cc: Paolo Abeni <pabeni@redhat.com>
>> Cc: Ido Schimmel <idosch@nvidia.com>
>> Cc: Petr Machata <petrm@nvidia.com>
>> Cc: netdev@vger.kernel.org
>> ---
>>  net/core/rtnetlink.c | 22 +++++++---------------
>>  1 file changed, 7 insertions(+), 15 deletions(-)
>> 
>> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> index ab5f201bf0ab..6da0edc0870d 100644
>> --- a/net/core/rtnetlink.c
>> +++ b/net/core/rtnetlink.c
>> @@ -3048,21 +3048,13 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
>>  	}
>>  
>>  	if (tb[IFLA_ADDRESS]) {
>> -		struct sockaddr *sa;
>> -		int len;
>> -
>> -		len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
>> -						  sizeof(*sa));
>> -		sa = kmalloc(len, GFP_KERNEL);
>> -		if (!sa) {
>> -			err = -ENOMEM;
>> -			goto errout;
>> -		}
>> -		sa->sa_family = dev->type;
>> -		memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
>> -		       dev->addr_len);
>> -		err = dev_set_mac_address_user(dev, sa, extack);
>> -		kfree(sa);
>> +		struct sockaddr sa = { };
>> +
>> +		/* dev_set_mac_address_user() uses a true struct sockaddr. */
>> +		sa.sa_family = dev->type;
>> +		memcpy(sa.sa_data, nla_data(tb[IFLA_ADDRESS]),
>> +		       min(dev->addr_len, sizeof(sa.sa_data_min)));
>> +		err = dev_set_mac_address_user(dev, &sa, extack);
>>  		if (err)
>>  			goto errout;
>>  		status |= DO_SETLINK_MODIFIED;
>> -- 
>> 2.34.1
>

-- 
Kees Cook

Re: [PATCH] rtnetlink: do_setlink: Use true struct sockaddr

Posted by Kuniyuki Iwashima 1 year ago

From: Kees Cook <kees@kernel.org>
Date: Mon, 16 Dec 2024 23:53:46 -0800
> On December 16, 2024 6:41:56 PM PST, Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
> >From: Kees Cook <kees@kernel.org>
> >Date: Mon, 16 Dec 2024 18:04:45 -0800
> >> Instead of a heap allocation use a stack allocated struct sockaddr, as
> >> dev_set_mac_address_user() is the consumer (which uses a classic
> >> struct sockaddr).
> >
> >I remember Eric's feedback was to keep using heap instead of stack
> >because rtnl_newlink() path already uses too much on stack.
> 
> See below...
> 
> >
> >
> >> Cap the copy to the minimum address size between
> >> the incoming address and the traditional sa_data field itself.
> >> 
> >> Putting "sa" on the stack means it will get a reused stack slot since
> >> it is smaller than other existing single-scope stack variables (like
> >> the vfinfo array).
> 
> That's why I included the rationale above. (I.e. stack usage does not grow with this patch.)

Ah okay, but I think we can't cap the address size to 14
bytes.  MAX_ADDR_LEN is 32.

Also, dev_set_mac_address_user() still uses dev->addr_len.


> 
> -Kees
> 
> >> 
> >> Signed-off-by: Kees Cook <kees@kernel.org>
> >> ---
> >> Cc: Eric Dumazet <edumazet@google.com>
> >> Cc: "David S. Miller" <davem@davemloft.net>
> >> Cc: Jakub Kicinski <kuba@kernel.org>
> >> Cc: Paolo Abeni <pabeni@redhat.com>
> >> Cc: Ido Schimmel <idosch@nvidia.com>
> >> Cc: Petr Machata <petrm@nvidia.com>
> >> Cc: netdev@vger.kernel.org
> >> ---
> >>  net/core/rtnetlink.c | 22 +++++++---------------
> >>  1 file changed, 7 insertions(+), 15 deletions(-)
> >> 
> >> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> >> index ab5f201bf0ab..6da0edc0870d 100644
> >> --- a/net/core/rtnetlink.c
> >> +++ b/net/core/rtnetlink.c
> >> @@ -3048,21 +3048,13 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
> >>  	}
> >>  
> >>  	if (tb[IFLA_ADDRESS]) {
> >> -		struct sockaddr *sa;
> >> -		int len;
> >> -
> >> -		len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
> >> -						  sizeof(*sa));
> >> -		sa = kmalloc(len, GFP_KERNEL);
> >> -		if (!sa) {
> >> -			err = -ENOMEM;
> >> -			goto errout;
> >> -		}
> >> -		sa->sa_family = dev->type;
> >> -		memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
> >> -		       dev->addr_len);
> >> -		err = dev_set_mac_address_user(dev, sa, extack);
> >> -		kfree(sa);
> >> +		struct sockaddr sa = { };
> >> +
> >> +		/* dev_set_mac_address_user() uses a true struct sockaddr. */
> >> +		sa.sa_family = dev->type;
> >> +		memcpy(sa.sa_data, nla_data(tb[IFLA_ADDRESS]),
> >> +		       min(dev->addr_len, sizeof(sa.sa_data_min)));
> >> +		err = dev_set_mac_address_user(dev, &sa, extack);
> >>  		if (err)
> >>  			goto errout;
> >>  		status |= DO_SETLINK_MODIFIED;
> >> -- 
> >> 2.34.1
> >
> 
> -- 
> Kees Cook

Re: [PATCH] rtnetlink: do_setlink: Use true struct sockaddr

Posted by Kees Cook 1 year ago


On December 17, 2024 12:03:35 AM PST, Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>From: Kees Cook <kees@kernel.org>
>Date: Mon, 16 Dec 2024 23:53:46 -0800
>> On December 16, 2024 6:41:56 PM PST, Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
>> >From: Kees Cook <kees@kernel.org>
>> >Date: Mon, 16 Dec 2024 18:04:45 -0800
>> >> Instead of a heap allocation use a stack allocated struct sockaddr, as
>> >> dev_set_mac_address_user() is the consumer (which uses a classic
>> >> struct sockaddr).
>> >
>> >I remember Eric's feedback was to keep using heap instead of stack
>> >because rtnl_newlink() path already uses too much on stack.
>> 
>> See below...
>> 
>> >
>> >
>> >> Cap the copy to the minimum address size between
>> >> the incoming address and the traditional sa_data field itself.
>> >> 
>> >> Putting "sa" on the stack means it will get a reused stack slot since
>> >> it is smaller than other existing single-scope stack variables (like
>> >> the vfinfo array).
>> 
>> That's why I included the rationale above. (I.e. stack usage does not grow with this patch.)
>
>Ah okay, but I think we can't cap the address size to 14
>bytes.  MAX_ADDR_LEN is 32.
>
>Also, dev_set_mac_address_user() still uses dev->addr_len.

Oh, hrm, yes, that's true. I had audited callers of dev_set_mac_address(), but I think I must have missed callers of dev_set_mac_address_user(). Ugh. :( Let me take another look at this...

-Kees

>
>
>> 
>> -Kees
>> 
>> >> 
>> >> Signed-off-by: Kees Cook <kees@kernel.org>
>> >> ---
>> >> Cc: Eric Dumazet <edumazet@google.com>
>> >> Cc: "David S. Miller" <davem@davemloft.net>
>> >> Cc: Jakub Kicinski <kuba@kernel.org>
>> >> Cc: Paolo Abeni <pabeni@redhat.com>
>> >> Cc: Ido Schimmel <idosch@nvidia.com>
>> >> Cc: Petr Machata <petrm@nvidia.com>
>> >> Cc: netdev@vger.kernel.org
>> >> ---
>> >>  net/core/rtnetlink.c | 22 +++++++---------------
>> >>  1 file changed, 7 insertions(+), 15 deletions(-)
>> >> 
>> >> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> >> index ab5f201bf0ab..6da0edc0870d 100644
>> >> --- a/net/core/rtnetlink.c
>> >> +++ b/net/core/rtnetlink.c
>> >> @@ -3048,21 +3048,13 @@ static int do_setlink(const struct sk_buff *skb, struct net_device *dev,
>> >>  	}
>> >>  
>> >>  	if (tb[IFLA_ADDRESS]) {
>> >> -		struct sockaddr *sa;
>> >> -		int len;
>> >> -
>> >> -		len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
>> >> -						  sizeof(*sa));
>> >> -		sa = kmalloc(len, GFP_KERNEL);
>> >> -		if (!sa) {
>> >> -			err = -ENOMEM;
>> >> -			goto errout;
>> >> -		}
>> >> -		sa->sa_family = dev->type;
>> >> -		memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
>> >> -		       dev->addr_len);
>> >> -		err = dev_set_mac_address_user(dev, sa, extack);
>> >> -		kfree(sa);
>> >> +		struct sockaddr sa = { };
>> >> +
>> >> +		/* dev_set_mac_address_user() uses a true struct sockaddr. */
>> >> +		sa.sa_family = dev->type;
>> >> +		memcpy(sa.sa_data, nla_data(tb[IFLA_ADDRESS]),
>> >> +		       min(dev->addr_len, sizeof(sa.sa_data_min)));
>> >> +		err = dev_set_mac_address_user(dev, &sa, extack);
>> >>  		if (err)
>> >>  			goto errout;
>> >>  		status |= DO_SETLINK_MODIFIED;
>> >> -- 
>> >> 2.34.1
>> >
>> 
>> -- 
>> Kees Cook

-- 
Kees Cook