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linux-pinenote/net/unix/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

328 lines
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#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/sock_diag.h>
#include <linux/unix_diag.h>
#include <linux/skbuff.h>
#include <linux/module.h>
#include <net/netlink.h>
#include <net/af_unix.h>
#include <net/tcp_states.h>
static int sk_diag_dump_name(struct sock *sk, struct sk_buff *nlskb)
{
struct unix_address *addr = unix_sk(sk)->addr;
if (!addr)
return 0;
return nla_put(nlskb, UNIX_DIAG_NAME, addr->len - sizeof(short),
addr->name->sun_path);
}
static int sk_diag_dump_vfs(struct sock *sk, struct sk_buff *nlskb)
{
struct dentry *dentry = unix_sk(sk)->path.dentry;
if (dentry) {
struct unix_diag_vfs uv = {
.udiag_vfs_ino = dentry->d_inode->i_ino,
.udiag_vfs_dev = dentry->d_sb->s_dev,
};
return nla_put(nlskb, UNIX_DIAG_VFS, sizeof(uv), &uv);
}
return 0;
}
static int sk_diag_dump_peer(struct sock *sk, struct sk_buff *nlskb)
{
struct sock *peer;
int ino;
peer = unix_peer_get(sk);
if (peer) {
unix_state_lock(peer);
ino = sock_i_ino(peer);
unix_state_unlock(peer);
sock_put(peer);
return nla_put_u32(nlskb, UNIX_DIAG_PEER, ino);
}
return 0;
}
static int sk_diag_dump_icons(struct sock *sk, struct sk_buff *nlskb)
{
struct sk_buff *skb;
struct nlattr *attr;
u32 *buf;
int i;
if (sk->sk_state == TCP_LISTEN) {
spin_lock(&sk->sk_receive_queue.lock);
attr = nla_reserve(nlskb, UNIX_DIAG_ICONS,
sk->sk_receive_queue.qlen * sizeof(u32));
if (!attr)
goto errout;
buf = nla_data(attr);
i = 0;
skb_queue_walk(&sk->sk_receive_queue, skb) {
struct sock *req, *peer;
req = skb->sk;
/*
* The state lock is outer for the same sk's
* queue lock. With the other's queue locked it's
* OK to lock the state.
*/
unix_state_lock_nested(req);
peer = unix_sk(req)->peer;
buf[i++] = (peer ? sock_i_ino(peer) : 0);
unix_state_unlock(req);
}
spin_unlock(&sk->sk_receive_queue.lock);
}
return 0;
errout:
spin_unlock(&sk->sk_receive_queue.lock);
return -EMSGSIZE;
}
static int sk_diag_show_rqlen(struct sock *sk, struct sk_buff *nlskb)
{
struct unix_diag_rqlen rql;
if (sk->sk_state == TCP_LISTEN) {
rql.udiag_rqueue = sk->sk_receive_queue.qlen;
rql.udiag_wqueue = sk->sk_max_ack_backlog;
} else {
rql.udiag_rqueue = (u32) unix_inq_len(sk);
rql.udiag_wqueue = (u32) unix_outq_len(sk);
}
return nla_put(nlskb, UNIX_DIAG_RQLEN, sizeof(rql), &rql);
}
static int sk_diag_fill(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req,
u32 portid, u32 seq, u32 flags, int sk_ino)
{
struct nlmsghdr *nlh;
struct unix_diag_msg *rep;
nlh = nlmsg_put(skb, portid, seq, SOCK_DIAG_BY_FAMILY, sizeof(*rep),
flags);
if (!nlh)
return -EMSGSIZE;
rep = nlmsg_data(nlh);
rep->udiag_family = AF_UNIX;
rep->udiag_type = sk->sk_type;
rep->udiag_state = sk->sk_state;
rep->pad = 0;
rep->udiag_ino = sk_ino;
sock_diag_save_cookie(sk, rep->udiag_cookie);
if ((req->udiag_show & UDIAG_SHOW_NAME) &&
sk_diag_dump_name(sk, skb))
goto out_nlmsg_trim;
if ((req->udiag_show & UDIAG_SHOW_VFS) &&
sk_diag_dump_vfs(sk, skb))
goto out_nlmsg_trim;
if ((req->udiag_show & UDIAG_SHOW_PEER) &&
sk_diag_dump_peer(sk, skb))
goto out_nlmsg_trim;
if ((req->udiag_show & UDIAG_SHOW_ICONS) &&
sk_diag_dump_icons(sk, skb))
goto out_nlmsg_trim;
if ((req->udiag_show & UDIAG_SHOW_RQLEN) &&
sk_diag_show_rqlen(sk, skb))
goto out_nlmsg_trim;
if ((req->udiag_show & UDIAG_SHOW_MEMINFO) &&
sock_diag_put_meminfo(sk, skb, UNIX_DIAG_MEMINFO))
goto out_nlmsg_trim;
if (nla_put_u8(skb, UNIX_DIAG_SHUTDOWN, sk->sk_shutdown))
goto out_nlmsg_trim;
nlmsg_end(skb, nlh);
return 0;
out_nlmsg_trim:
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}
static int sk_diag_dump(struct sock *sk, struct sk_buff *skb, struct unix_diag_req *req,
u32 portid, u32 seq, u32 flags)
{
int sk_ino;
unix_state_lock(sk);
sk_ino = sock_i_ino(sk);
unix_state_unlock(sk);
if (!sk_ino)
return 0;
return sk_diag_fill(sk, skb, req, portid, seq, flags, sk_ino);
}
static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
struct unix_diag_req *req;
int num, s_num, slot, s_slot;
struct net *net = sock_net(skb->sk);
req = nlmsg_data(cb->nlh);
s_slot = cb->args[0];
num = s_num = cb->args[1];
spin_lock(&unix_table_lock);
for (slot = s_slot;
slot < ARRAY_SIZE(unix_socket_table);
s_num = 0, slot++) {
struct sock *sk;
num = 0;
sk_for_each(sk, &unix_socket_table[slot]) {
if (!net_eq(sock_net(sk), net))
continue;
if (num < s_num)
goto next;
if (!(req->udiag_states & (1 << sk->sk_state)))
goto next;
if (sk_diag_dump(sk, skb, req,
NETLINK_CB(cb->skb).portid,
cb->nlh->nlmsg_seq,
NLM_F_MULTI) < 0)
goto done;
next:
num++;
}
}
done:
spin_unlock(&unix_table_lock);
cb->args[0] = slot;
cb->args[1] = num;
return skb->len;
}
static struct sock *unix_lookup_by_ino(int ino)
{
int i;
struct sock *sk;
spin_lock(&unix_table_lock);
for (i = 0; i < ARRAY_SIZE(unix_socket_table); i++) {
sk_for_each(sk, &unix_socket_table[i])
if (ino == sock_i_ino(sk)) {
sock_hold(sk);
spin_unlock(&unix_table_lock);
return sk;
}
}
spin_unlock(&unix_table_lock);
return NULL;
}
static int unix_diag_get_exact(struct sk_buff *in_skb,
const struct nlmsghdr *nlh,
struct unix_diag_req *req)
{
int err = -EINVAL;
struct sock *sk;
struct sk_buff *rep;
unsigned int extra_len;
struct net *net = sock_net(in_skb->sk);
if (req->udiag_ino == 0)
goto out_nosk;
sk = unix_lookup_by_ino(req->udiag_ino);
err = -ENOENT;
if (sk == NULL)
goto out_nosk;
err = sock_diag_check_cookie(sk, req->udiag_cookie);
if (err)
goto out;
extra_len = 256;
again:
err = -ENOMEM;
rep = nlmsg_new(sizeof(struct unix_diag_msg) + extra_len, GFP_KERNEL);
if (!rep)
goto out;
err = sk_diag_fill(sk, rep, req, NETLINK_CB(in_skb).portid,
nlh->nlmsg_seq, 0, req->udiag_ino);
if (err < 0) {
nlmsg_free(rep);
extra_len += 256;
if (extra_len >= PAGE_SIZE)
goto out;
goto again;
}
err = netlink_unicast(net->diag_nlsk, rep, NETLINK_CB(in_skb).portid,
MSG_DONTWAIT);
if (err > 0)
err = 0;
out:
if (sk)
sock_put(sk);
out_nosk:
return err;
}
static int unix_diag_handler_dump(struct sk_buff *skb, struct nlmsghdr *h)
{
int hdrlen = sizeof(struct unix_diag_req);
struct net *net = sock_net(skb->sk);
if (nlmsg_len(h) < hdrlen)
return -EINVAL;
if (h->nlmsg_flags & NLM_F_DUMP) {
struct netlink_dump_control c = {
.dump = unix_diag_dump,
};
return netlink_dump_start(net->diag_nlsk, skb, h, &c);
} else
return unix_diag_get_exact(skb, h, nlmsg_data(h));
}
static const struct sock_diag_handler unix_diag_handler = {
.family = AF_UNIX,
.dump = unix_diag_handler_dump,
};
static int __init unix_diag_init(void)
{
return sock_diag_register(&unix_diag_handler);
}
static void __exit unix_diag_exit(void)
{
sock_diag_unregister(&unix_diag_handler);
}
module_init(unix_diag_init);
module_exit(unix_diag_exit);
MODULE_LICENSE("GPL");
MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_NETLINK, NETLINK_SOCK_DIAG, 1 /* AF_LOCAL */);
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