Commit f3d33426 authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by David S. Miller
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net: rework recvmsg handler msg_name and msg_namelen logic 



This patch now always passes msg->msg_namelen as 0. recvmsg handlers must
set msg_namelen to the proper size <= sizeof(struct sockaddr_storage)
to return msg_name to the user.

This prevents numerous uninitialized memory leaks we had in the
recvmsg handlers and makes it harder for new code to accidentally leak
uninitialized memory.

Optimize for the case recvfrom is called with NULL as address. We don't
need to copy the address at all, so set it to NULL before invoking the
recvmsg handler. We can do so, because all the recvmsg handlers must
cope with the case a plain read() is called on them. read() also sets
msg_name to NULL.

Also document these changes in include/linux/net.h as suggested by David
Miller.

Changes since RFC:

Set msg->msg_name = NULL if user specified a NULL in msg_name but had a
non-null msg_namelen in verify_iovec/verify_compat_iovec. This doesn't
affect sendto as it would bail out earlier while trying to copy-in the
address. It also more naturally reflects the logic by the callers of
verify_iovec.

With this change in place I could remove "
if (!uaddr || msg_sys->msg_namelen == 0)
	msg->msg_name = NULL
".

This change does not alter the user visible error logic as we ignore
msg_namelen as long as msg_name is NULL.

Also remove two unnecessary curly brackets in ___sys_recvmsg and change
comments to netdev style.

Cc: David Miller <davem@davemloft.net>
Suggested-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f8730420

crypto/algif_hash.c

+0 −2
Original line number Diff line number Diff line
@@ -161,8 +161,6 @@ static int hash_recvmsg(struct kiocb *unused, struct socket *sock, 
	else if (len < ds)

		msg->msg_flags |= MSG_TRUNC;



	msg->msg_namelen = 0;



	lock_sock(sk);

	if (ctx->more) {

		ctx->more = 0;

crypto/algif_skcipher.c

+0 −1
Original line number Diff line number Diff line
@@ -432,7 +432,6 @@ static int skcipher_recvmsg(struct kiocb *unused, struct socket *sock, 
	long copied = 0;



	lock_sock(sk);

	msg->msg_namelen = 0;

	for (iov = msg->msg_iov, iovlen = msg->msg_iovlen; iovlen > 0;

	     iovlen--, iov++) {

		unsigned long seglen = iov->iov_len;

drivers/isdn/mISDN/socket.c

+4 −9
Original line number Diff line number Diff line
@@ -117,7 +117,6 @@ mISDN_sock_recvmsg(struct kiocb *iocb, struct socket *sock, 
{

	struct sk_buff		*skb;

	struct sock		*sk = sock->sk;

	struct sockaddr_mISDN	*maddr;



	int		copied, err;
@@ -135,9 +134,9 @@ mISDN_sock_recvmsg(struct kiocb *iocb, struct socket *sock, 
	if (!skb)

		return err;



	if (msg->msg_namelen >= sizeof(struct sockaddr_mISDN)) {

		msg->msg_namelen = sizeof(struct sockaddr_mISDN);

		maddr = (struct sockaddr_mISDN *)msg->msg_name;

	if (msg->msg_name) {

		struct sockaddr_mISDN *maddr = msg->msg_name;



		maddr->family = AF_ISDN;

		maddr->dev = _pms(sk)->dev->id;

		if ((sk->sk_protocol == ISDN_P_LAPD_TE) ||
@@ -150,11 +149,7 @@ mISDN_sock_recvmsg(struct kiocb *iocb, struct socket *sock, 
			maddr->sapi = _pms(sk)->ch.addr & 0xFF;

			maddr->tei =  (_pms(sk)->ch.addr >> 8) & 0xFF;

		}

	} else {

		if (msg->msg_namelen)

			printk(KERN_WARNING "%s: too small namelen %d\n",

			       __func__, msg->msg_namelen);

		msg->msg_namelen = 0;

		msg->msg_namelen = sizeof(*maddr);

	}



	copied = skb->len + MISDN_HEADER_LEN;

drivers/net/ppp/pppoe.c

+0 −2
Original line number Diff line number Diff line
@@ -979,8 +979,6 @@ static int pppoe_recvmsg(struct kiocb *iocb, struct socket *sock, 
	if (error < 0)

		goto end;



	m->msg_namelen = 0;



	if (skb) {

		total_len = min_t(size_t, total_len, skb->len);

		error = skb_copy_datagram_iovec(skb, 0, m->msg_iov, total_len);

include/linux/net.h

+8 −0
Original line number Diff line number Diff line
@@ -164,6 +164,14 @@ struct proto_ops { 
#endif

	int		(*sendmsg)   (struct kiocb *iocb, struct socket *sock,

				      struct msghdr *m, size_t total_len);

	/* Notes for implementing recvmsg:

	 * ===============================

	 * msg->msg_namelen should get updated by the recvmsg handlers

	 * iff msg_name != NULL. It is by default 0 to prevent

	 * returning uninitialized memory to user space.  The recvfrom

	 * handlers can assume that msg.msg_name is either NULL or has

	 * a minimum size of sizeof(struct sockaddr_storage).

	 */

	int		(*recvmsg)   (struct kiocb *iocb, struct socket *sock,

				      struct msghdr *m, size_t total_len,

				      int flags);

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