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linux-pinenote/net/packet/diag.c
Johannes Berg 053c095a82 netlink: make nlmsg_end() and genlmsg_end() void 
Contrary to common expectations for an "int" return, these functions
return only a positive value -- if used correctly they cannot even
return 0 because the message header will necessarily be in the skb.

This makes the very common pattern of

  if (genlmsg_end(...) < 0) { ... }

be a whole bunch of dead code. Many places also simply do

  return nlmsg_end(...);

and the caller is expected to deal with it.

This also commonly (at least for me) causes errors, because it is very
common to write

  if (my_function(...))
    /* error condition */

and if my_function() does "return nlmsg_end()" this is of course wrong.

Additionally, there's not a single place in the kernel that actually
needs the message length returned, and if anyone needs it later then
it'll be very easy to just use skb->len there.

Remove this, and make the functions void. This removes a bunch of dead
code as described above. The patch adds lines because I did

-	return nlmsg_end(...);
+	nlmsg_end(...);
+	return 0;

I could have preserved all the function's return values by returning
skb->len, but instead I've audited all the places calling the affected
functions and found that none cared. A few places actually compared
the return value with <= 0 in dump functionality, but that could just
be changed to < 0 with no change in behaviour, so I opted for the more
efficient version.

One instance of the error I've made numerous times now is also present
in net/phonet/pn_netlink.c in the route_dumpit() function - it didn't
check for <0 or <=0 and thus broke out of the loop every single time.
I've preserved this since it will (I think) have caused the messages to
userspace to be formatted differently with just a single message for
every SKB returned to userspace. It's possible that this isn't needed
for the tools that actually use this, but I don't even know what they
are so couldn't test that changing this behaviour would be acceptable.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-01-18 01:03:45 -05:00

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#include <linux/module.h>
#include <linux/sock_diag.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/packet_diag.h>
#include <linux/percpu.h>
#include <net/net_namespace.h>
#include <net/sock.h>
#include "internal.h"
static int pdiag_put_info(const struct packet_sock *po, struct sk_buff *nlskb)
{
struct packet_diag_info pinfo;
pinfo.pdi_index = po->ifindex;
pinfo.pdi_version = po->tp_version;
pinfo.pdi_reserve = po->tp_reserve;
pinfo.pdi_copy_thresh = po->copy_thresh;
pinfo.pdi_tstamp = po->tp_tstamp;
pinfo.pdi_flags = 0;
if (po->running)
pinfo.pdi_flags |= PDI_RUNNING;
if (po->auxdata)
pinfo.pdi_flags |= PDI_AUXDATA;
if (po->origdev)
pinfo.pdi_flags |= PDI_ORIGDEV;
if (po->has_vnet_hdr)
pinfo.pdi_flags |= PDI_VNETHDR;
if (po->tp_loss)
pinfo.pdi_flags |= PDI_LOSS;
return nla_put(nlskb, PACKET_DIAG_INFO, sizeof(pinfo), &pinfo);
}
static int pdiag_put_mclist(const struct packet_sock *po, struct sk_buff *nlskb)
{
struct nlattr *mca;
struct packet_mclist *ml;
mca = nla_nest_start(nlskb, PACKET_DIAG_MCLIST);
if (!mca)
return -EMSGSIZE;
rtnl_lock();
for (ml = po->mclist; ml; ml = ml->next) {
struct packet_diag_mclist *dml;
dml = nla_reserve_nohdr(nlskb, sizeof(*dml));
if (!dml) {
rtnl_unlock();
nla_nest_cancel(nlskb, mca);
return -EMSGSIZE;
}
dml->pdmc_index = ml->ifindex;
dml->pdmc_type = ml->type;
dml->pdmc_alen = ml->alen;
dml->pdmc_count = ml->count;
BUILD_BUG_ON(sizeof(dml->pdmc_addr) != sizeof(ml->addr));
memcpy(dml->pdmc_addr, ml->addr, sizeof(ml->addr));
}
rtnl_unlock();
nla_nest_end(nlskb, mca);
return 0;
}
static int pdiag_put_ring(struct packet_ring_buffer *ring, int ver, int nl_type,
struct sk_buff *nlskb)
{
struct packet_diag_ring pdr;
if (!ring->pg_vec || ((ver > TPACKET_V2) &&
(nl_type == PACKET_DIAG_TX_RING)))
return 0;
pdr.pdr_block_size = ring->pg_vec_pages << PAGE_SHIFT;
pdr.pdr_block_nr = ring->pg_vec_len;
pdr.pdr_frame_size = ring->frame_size;
pdr.pdr_frame_nr = ring->frame_max + 1;
if (ver > TPACKET_V2) {
pdr.pdr_retire_tmo = ring->prb_bdqc.retire_blk_tov;
pdr.pdr_sizeof_priv = ring->prb_bdqc.blk_sizeof_priv;
pdr.pdr_features = ring->prb_bdqc.feature_req_word;
} else {
pdr.pdr_retire_tmo = 0;
pdr.pdr_sizeof_priv = 0;
pdr.pdr_features = 0;
}
return nla_put(nlskb, nl_type, sizeof(pdr), &pdr);
}
static int pdiag_put_rings_cfg(struct packet_sock *po, struct sk_buff *skb)
{
int ret;
mutex_lock(&po->pg_vec_lock);
ret = pdiag_put_ring(&po->rx_ring, po->tp_version,
PACKET_DIAG_RX_RING, skb);
if (!ret)
ret = pdiag_put_ring(&po->tx_ring, po->tp_version,
PACKET_DIAG_TX_RING, skb);
mutex_unlock(&po->pg_vec_lock);
return ret;
}
static int pdiag_put_fanout(struct packet_sock *po, struct sk_buff *nlskb)
{
int ret = 0;
mutex_lock(&fanout_mutex);
if (po->fanout) {
u32 val;
val = (u32)po->fanout->id | ((u32)po->fanout->type << 16);
ret = nla_put_u32(nlskb, PACKET_DIAG_FANOUT, val);
}
mutex_unlock(&fanout_mutex);
return ret;
}
static int sk_diag_fill(struct sock *sk, struct sk_buff *skb,
struct packet_diag_req *req,
bool may_report_filterinfo,
struct user_namespace *user_ns,
u32 portid, u32 seq, u32 flags, int sk_ino)
{
struct nlmsghdr *nlh;
struct packet_diag_msg *rp;
struct packet_sock *po = pkt_sk(sk);
nlh = nlmsg_put(skb, portid, seq, SOCK_DIAG_BY_FAMILY, sizeof(*rp), flags);
if (!nlh)
return -EMSGSIZE;
rp = nlmsg_data(nlh);
rp->pdiag_family = AF_PACKET;
rp->pdiag_type = sk->sk_type;
rp->pdiag_num = ntohs(po->num);
rp->pdiag_ino = sk_ino;
sock_diag_save_cookie(sk, rp->pdiag_cookie);
if ((req->pdiag_show & PACKET_SHOW_INFO) &&
pdiag_put_info(po, skb))
goto out_nlmsg_trim;
if ((req->pdiag_show & PACKET_SHOW_INFO) &&
nla_put_u32(skb, PACKET_DIAG_UID,
from_kuid_munged(user_ns, sock_i_uid(sk))))
goto out_nlmsg_trim;
if ((req->pdiag_show & PACKET_SHOW_MCLIST) &&
pdiag_put_mclist(po, skb))
goto out_nlmsg_trim;
if ((req->pdiag_show & PACKET_SHOW_RING_CFG) &&
pdiag_put_rings_cfg(po, skb))
goto out_nlmsg_trim;
if ((req->pdiag_show & PACKET_SHOW_FANOUT) &&
pdiag_put_fanout(po, skb))
goto out_nlmsg_trim;
if ((req->pdiag_show & PACKET_SHOW_MEMINFO) &&
sock_diag_put_meminfo(sk, skb, PACKET_DIAG_MEMINFO))
goto out_nlmsg_trim;
if ((req->pdiag_show & PACKET_SHOW_FILTER) &&
sock_diag_put_filterinfo(may_report_filterinfo, sk, skb,
PACKET_DIAG_FILTER))
goto out_nlmsg_trim;
nlmsg_end(skb, nlh);
return 0;
out_nlmsg_trim:
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}
static int packet_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
int num = 0, s_num = cb->args[0];
struct packet_diag_req *req;
struct net *net;
struct sock *sk;
bool may_report_filterinfo;
net = sock_net(skb->sk);
req = nlmsg_data(cb->nlh);
may_report_filterinfo = netlink_net_capable(cb->skb, CAP_NET_ADMIN);
mutex_lock(&net->packet.sklist_lock);
sk_for_each(sk, &net->packet.sklist) {
if (!net_eq(sock_net(sk), net))
continue;
if (num < s_num)
goto next;
if (sk_diag_fill(sk, skb, req,
may_report_filterinfo,
sk_user_ns(NETLINK_CB(cb->skb).sk),
NETLINK_CB(cb->skb).portid,
cb->nlh->nlmsg_seq, NLM_F_MULTI,
sock_i_ino(sk)) < 0)
goto done;
next:
num++;
}
done:
mutex_unlock(&net->packet.sklist_lock);
cb->args[0] = num;
return skb->len;
}
static int packet_diag_handler_dump(struct sk_buff *skb, struct nlmsghdr *h)
{
int hdrlen = sizeof(struct packet_diag_req);
struct net *net = sock_net(skb->sk);
struct packet_diag_req *req;
if (nlmsg_len(h) < hdrlen)
return -EINVAL;
req = nlmsg_data(h);
/* Make it possible to support protocol filtering later */
if (req->sdiag_protocol)
return -EINVAL;
if (h->nlmsg_flags & NLM_F_DUMP) {
struct netlink_dump_control c = {
.dump = packet_diag_dump,
};
return netlink_dump_start(net->diag_nlsk, skb, h, &c);
} else
return -EOPNOTSUPP;
}
static const struct sock_diag_handler packet_diag_handler = {
.family = AF_PACKET,
.dump = packet_diag_handler_dump,
};
static int __init packet_diag_init(void)
{
return sock_diag_register(&packet_diag_handler);
}
static void __exit packet_diag_exit(void)
{
sock_diag_unregister(&packet_diag_handler);
}
module_init(packet_diag_init);
module_exit(packet_diag_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_NETLINK, NETLINK_SOCK_DIAG, 17 /* AF_PACKET */);
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