Re: PATCH: Breaking UAPI change?

[Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>]

On Wed, 24 Mar 2021 21:26:19 +0100, Oliver Hartkopp wrote:
> On 24.03.21 20:27, Kurt Van Dijck wrote:
> >>----- Ursprüngliche Mail -----
> >>>>commit f5223e9eee65 ("can: extend sockaddr_can to include j1939 members")
> >commit 124900109ca88d29382ef2e2b848d3a2f9d67b98
> >Author: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
> >Date:   Wed Mar 24 20:08:50 2021
> >
> >     can raw: don't increase provided name length
> >     The length of the buffer is known by the application,
> >     not the kernel. Kernel is supposed to return only the
> >     size of used bytes.
> >     There is a minimum required size for the struct sockaddr_can
> >     to be usefull for can_raw, so errors are returned when
> >     the provided size is lower
> >     Signed-off-by: Kurt Van Dijck <dev.kurt@vandijck-laurijssen.be>
> >
> >diff --git a/net/can/raw.c b/net/can/raw.c
> >index 6ec8aa1d0da4..00d352ae221e 100644
> >--- a/net/can/raw.c
> >+++ b/net/can/raw.c
> >@@ -475,7 +475,7 @@ static int raw_getname(struct socket *sock, struct sockaddr *uaddr,
> >  	if (peer)
> >  		return -EOPNOTSUPP;
> >-	memset(addr, 0, sizeof(*addr));
> >+	memset(addr, 0, CAN_REQUIRED_SIZE(*addr, ifindex));
> >  	addr->can_family  = AF_CAN;
> >  	addr->can_ifindex = ro->ifindex;
> 
> Is there no need to adapt the return value then?
> 
> - return sizeof(*addr);
> + return CAN_REQUIRED_SIZE(*addr, ifindex);

indeed. I have missed that one.
I was looking for a function parameter, and then forgot somehow ...

> 
> Regards,
> Oliver
> 
> ps. If so, I need to go through isotp_getname() too ...
> 
> 
> >@@ -806,6 +806,10 @@ static int raw_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> >  		return sock_recv_errqueue(sk, msg, size,
> >  					  SOL_CAN_RAW, SCM_CAN_RAW_ERRQUEUE);
> >+	if (msg->name && msg->msg_namelen <
> >+			CAN_REQUIRED_SIZE(struct sockaddr_can, ifindex))
> >+		return -EINVAL;
> >+
> >  	skb = skb_recv_datagram(sk, flags, noblock, &err);
> >  	if (!skb)
> >  		return err;
> >@@ -825,7 +829,8 @@ static int raw_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
> >  	if (msg->msg_name) {
> >  		__sockaddr_check_size(sizeof(struct sockaddr_can));
> >-		msg->msg_namelen = sizeof(struct sockaddr_can);
> >+		if (msg->msg_namelen > sizeof(struct sockaddr_can))
> >+			msg->msg_namelen = sizeof(struct sockaddr_can);
> >  		memcpy(msg->msg_name, skb->cb, msg->msg_namelen);
> >  	}
> >