nl80211: use small state buffer for wiphy_dump

Avoid parsing the original dump message again and again by
allocating a small state struct that is used by the functions
involved in the dump, storing this struct in cb->args[0].
This reduces the memory allocation size as well.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 116 insertions, 94 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index f8ffb9a59c83..7dc3343427c1 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -1111,10 +1111,16 @@ nl80211_send_mgmt_stypes(struct sk_buff *msg,
         return 0;
 }
 
+struct nl80211_dump_wiphy_state {
+        s64 filter_wiphy;
+        long start;
+        long split_start, band_start, chan_start;
+        bool split;
+};
+
 static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                               struct sk_buff *msg, u32 portid, u32 seq,
-                              int flags, bool split, long *split_start,
-                              long *band_start, long *chan_start)
+                              int flags, struct nl80211_dump_wiphy_state *state)
 {
         void *hdr;
         struct nlattr *nl_bands, *nl_band;
@@ -1125,19 +1131,14 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
         int i;
         const struct ieee80211_txrx_stypes *mgmt_stypes =
                                 dev->wiphy.mgmt_stypes;
-        long start = 0, start_chan = 0, start_band = 0;
         u32 features;
 
         hdr = nl80211hdr_put(msg, portid, seq, flags, NL80211_CMD_NEW_WIPHY);
         if (!hdr)
                 return -ENOBUFS;
 
-        /* allow always using the variables */
-        if (!split) {
-                split_start = &start;
-                band_start = &start_band;
-                chan_start = &start_chan;
-        }
+        if (WARN_ON(!state))
+                return -EINVAL;
 
         if (nla_put_u32(msg, NL80211_ATTR_WIPHY, dev->wiphy_idx) ||
             nla_put_string(msg, NL80211_ATTR_WIPHY_NAME,
@@ -1146,7 +1147,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                         cfg80211_rdev_list_generation))
                 goto nla_put_failure;
 
-        switch (*split_start) {
+        switch (state->split_start) {
         case 0:
                 if (nla_put_u8(msg, NL80211_ATTR_WIPHY_RETRY_SHORT,
                                dev->wiphy.retry_short) ||
@@ -1192,8 +1193,8 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                     nla_put_flag(msg, WIPHY_FLAG_SUPPORTS_5_10_MHZ))
                         goto nla_put_failure;
 
-                (*split_start)++;
-                if (split)
+                state->split_start++;
+                if (state->split)
                         break;
         case 1:
                 if (nla_put(msg, NL80211_ATTR_CIPHER_SUITES,
@@ -1237,22 +1238,23 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                         }
                 }
 
-                (*split_start)++;
-                if (split)
+                state->split_start++;
+                if (state->split)
                         break;
         case 2:
                 if (nl80211_put_iftypes(msg, NL80211_ATTR_SUPPORTED_IFTYPES,
                                         dev->wiphy.interface_modes))
                                 goto nla_put_failure;
-                (*split_start)++;
-                if (split)
+                state->split_start++;
+                if (state->split)
                         break;
         case 3:
                 nl_bands = nla_nest_start(msg, NL80211_ATTR_WIPHY_BANDS);
                 if (!nl_bands)
                         goto nla_put_failure;
 
-                for (band = *band_start; band < IEEE80211_NUM_BANDS; band++) {
+                for (band = state->band_start;
+                     band < IEEE80211_NUM_BANDS; band++) {
                         struct ieee80211_supported_band *sband;
 
                         sband = dev->wiphy.bands[band];
@@ -1264,12 +1266,12 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                         if (!nl_band)
                                 goto nla_put_failure;
 
-                        switch (*chan_start) {
+                        switch (state->chan_start) {
                         case 0:
                                 if (nl80211_send_band_rateinfo(msg, sband))
                                         goto nla_put_failure;
-                                (*chan_start)++;
-                                if (split)
+                                state->chan_start++;
+                                if (state->split)
                                         break;
                         default:
                                 /* add frequencies */
@@ -1278,7 +1280,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                                 if (!nl_freqs)
                                         goto nla_put_failure;
 
-                                for (i = *chan_start - 1;
+                                for (i = state->chan_start - 1;
                                      i < sband->n_channels;
                                      i++) {
                                         nl_freq = nla_nest_start(msg, i);
@@ -1287,26 +1289,27 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
 
                                         chan = &sband->channels[i];
 
-                                        if (nl80211_msg_put_channel(msg, chan,
-                                                                    split))
+                                        if (nl80211_msg_put_channel(
+                                                        msg, chan,
+                                                        state->split))
                                                 goto nla_put_failure;
 
                                         nla_nest_end(msg, nl_freq);
-                                        if (split)
+                                        if (state->split)
                                                 break;
                                 }
                                 if (i < sband->n_channels)
-                                        *chan_start = i + 2;
+                                        state->chan_start = i + 2;
                                 else
-                                        *chan_start = 0;
+                                        state->chan_start = 0;
                                 nla_nest_end(msg, nl_freqs);
                         }
 
                         nla_nest_end(msg, nl_band);
 
-                        if (split) {
+                        if (state->split) {
                                 /* start again here */
-                                if (*chan_start)
+                                if (state->chan_start)
                                         band--;
                                 break;
                         }
@@ -1314,14 +1317,14 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                 nla_nest_end(msg, nl_bands);
 
                 if (band < IEEE80211_NUM_BANDS)
-                        *band_start = band + 1;
+                        state->band_start = band + 1;
                 else
-                        *band_start = 0;
+                        state->band_start = 0;
 
                 /* if bands & channels are done, continue outside */
-                if (*band_start == 0 && *chan_start == 0)
-                        (*split_start)++;
-                if (split)
+                if (state->band_start == 0 && state->chan_start == 0)
+                        state->split_start++;
+                if (state->split)
                         break;
         case 4:
                 nl_cmds = nla_nest_start(msg, NL80211_ATTR_SUPPORTED_COMMANDS);
@@ -1387,7 +1390,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                 }
                 CMD(start_p2p_device, START_P2P_DEVICE);
                 CMD(set_mcast_rate, SET_MCAST_RATE);
-                if (split) {
+                if (state->split) {
                         CMD(crit_proto_start, CRIT_PROTOCOL_START);
                         CMD(crit_proto_stop, CRIT_PROTOCOL_STOP);
                 }
@@ -1411,8 +1414,8 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                 }
 
                 nla_nest_end(msg, nl_cmds);
-                (*split_start)++;
-                if (split)
+                state->split_start++;
+                if (state->split)
                         break;
         case 5:
                 if (dev->ops->remain_on_channel &&
@@ -1428,29 +1431,30 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
 
                 if (nl80211_send_mgmt_stypes(msg, mgmt_stypes))
                         goto nla_put_failure;
-                (*split_start)++;
-                if (split)
+                state->split_start++;
+                if (state->split)
                         break;
         case 6:
 #ifdef CONFIG_PM
-                if (nl80211_send_wowlan(msg, dev, split))
+                if (nl80211_send_wowlan(msg, dev, state->split))
                         goto nla_put_failure;
-                (*split_start)++;
-                if (split)
+                state->split_start++;
+                if (state->split)
                         break;
 #else
-                (*split_start)++;
+                state->split_start++;
 #endif
         case 7:
                 if (nl80211_put_iftypes(msg, NL80211_ATTR_SOFTWARE_IFTYPES,
                                         dev->wiphy.software_iftypes))
                         goto nla_put_failure;
 
-                if (nl80211_put_iface_combinations(&dev->wiphy, msg, split))
+                if (nl80211_put_iface_combinations(&dev->wiphy, msg,
+                                                   state->split))
                         goto nla_put_failure;
 
-                (*split_start)++;
-                if (split)
+                state->split_start++;
+                if (state->split)
                         break;
         case 8:
                 if ((dev->wiphy.flags & WIPHY_FLAG_HAVE_AP_SME) &&
@@ -1464,7 +1468,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                  * dump is split, otherwise it makes it too big. Therefore
                  * only advertise it in that case.
                  */
-                if (split)
+                if (state->split)
                         features |= NL80211_FEATURE_ADVERTISE_CHAN_LIMITS;
                 if (nla_put_u32(msg, NL80211_ATTR_FEATURE_FLAGS, features))
                         goto nla_put_failure;
@@ -1491,7 +1495,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                  * case we'll continue with more data in the next round,
                  * but break unconditionally so unsplit data stops here.
                  */
-                (*split_start)++;
+                state->split_start++;
                 break;
         case 9:
                 if (dev->wiphy.extended_capabilities &&
@@ -1510,7 +1514,7 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
                         goto nla_put_failure;
 
                 /* done */
-                *split_start = 0;
+                state->split_start = 0;
                 break;
         }
         return genlmsg_end(msg, hdr);
@@ -1520,66 +1524,76 @@ static int nl80211_send_wiphy(struct cfg80211_registered_device *dev,
         return -EMSGSIZE;
 }
 
+static int nl80211_dump_wiphy_parse(struct sk_buff *skb,
+                                    struct netlink_callback *cb,
+                                    struct nl80211_dump_wiphy_state *state)
+{
+        struct nlattr **tb = nl80211_fam.attrbuf;
+        int ret = nlmsg_parse(cb->nlh, GENL_HDRLEN + nl80211_fam.hdrsize,
+                              tb, nl80211_fam.maxattr, nl80211_policy);
+        /* ignore parse errors for backward compatibility */
+        if (ret)
+                return 0;
+
+        state->split = tb[NL80211_ATTR_SPLIT_WIPHY_DUMP];
+        if (tb[NL80211_ATTR_WIPHY])
+                state->filter_wiphy = nla_get_u32(tb[NL80211_ATTR_WIPHY]);
+        if (tb[NL80211_ATTR_WDEV])
+                state->filter_wiphy = nla_get_u64(tb[NL80211_ATTR_WDEV]) >> 32;
+        if (tb[NL80211_ATTR_IFINDEX]) {
+                struct net_device *netdev;
+                struct cfg80211_registered_device *rdev;
+                int ifidx = nla_get_u32(tb[NL80211_ATTR_IFINDEX]);
+
+                netdev = dev_get_by_index(sock_net(skb->sk), ifidx);
+                if (!netdev)
+                        return -ENODEV;
+                if (netdev->ieee80211_ptr) {
+                        rdev = wiphy_to_dev(
+                                netdev->ieee80211_ptr->wiphy);
+                        state->filter_wiphy = rdev->wiphy_idx;
+                }
+                dev_put(netdev);
+        }
+
+        return 0;
+}
+
 static int nl80211_dump_wiphy(struct sk_buff *skb, struct netlink_callback *cb)
 {
         int idx = 0, ret;
-        int start = cb->args[0];
+        struct nl80211_dump_wiphy_state *state = (void *)cb->args[0];
         struct cfg80211_registered_device *dev;
-        s64 filter_wiphy = -1;
-        bool split = false;
-        struct nlattr **tb;
-        int res;
-
-        /* will be zeroed in nlmsg_parse() */
-        tb = kmalloc(sizeof(*tb) * (NL80211_ATTR_MAX + 1), GFP_KERNEL);
-        if (!tb)
-                return -ENOMEM;
 
         rtnl_lock();
-        res = nlmsg_parse(cb->nlh, GENL_HDRLEN + nl80211_fam.hdrsize,
-                          tb, NL80211_ATTR_MAX, nl80211_policy);
-        if (res == 0) {
-                split = tb[NL80211_ATTR_SPLIT_WIPHY_DUMP];
-                if (tb[NL80211_ATTR_WIPHY])
-                        filter_wiphy = nla_get_u32(tb[NL80211_ATTR_WIPHY]);
-                if (tb[NL80211_ATTR_WDEV])
-                        filter_wiphy = nla_get_u64(tb[NL80211_ATTR_WDEV]) >> 32;
-                if (tb[NL80211_ATTR_IFINDEX]) {
-                        struct net_device *netdev;
-                        int ifidx = nla_get_u32(tb[NL80211_ATTR_IFINDEX]);
-
-                        netdev = dev_get_by_index(sock_net(skb->sk), ifidx);
-                        if (!netdev) {
-                                rtnl_unlock();
-                                kfree(tb);
-                                return -ENODEV;
-                        }
-                        if (netdev->ieee80211_ptr) {
-                                dev = wiphy_to_dev(
-                                        netdev->ieee80211_ptr->wiphy);
-                                filter_wiphy = dev->wiphy_idx;
-                        }
-                        dev_put(netdev);
+        if (!state) {
+                state = kzalloc(sizeof(*state), GFP_KERNEL);
+                if (!state)
+                        return -ENOMEM;
+                state->filter_wiphy = -1;
+                ret = nl80211_dump_wiphy_parse(skb, cb, state);
+                if (ret) {
+                        kfree(state);
+                        rtnl_unlock();
+                        return ret;
                 }
+                cb->args[0] = (long)state;
         }
-        kfree(tb);
 
         list_for_each_entry(dev, &cfg80211_rdev_list, list) {
                 if (!net_eq(wiphy_net(&dev->wiphy), sock_net(skb->sk)))
                         continue;
-                if (++idx <= start)
+                if (++idx <= state->start)
                         continue;
-                if (filter_wiphy != -1 && dev->wiphy_idx != filter_wiphy)
+                if (state->filter_wiphy != -1 &&
+                    state->filter_wiphy != dev->wiphy_idx)
                         continue;
                 /* attempt to fit multiple wiphy data chunks into the skb */
                 do {
                         ret = nl80211_send_wiphy(dev, skb,
                                                  NETLINK_CB(cb->skb).portid,
                                                  cb->nlh->nlmsg_seq,
-                                                 NLM_F_MULTI,
-                                                 split, &cb->args[1],
-                                                 &cb->args[2],
-                                                 &cb->args[3]);
+                                                 NLM_F_MULTI, state);
                         if (ret < 0) {
                                 /*
                                  * If sending the wiphy data didn't fit (ENOBUFS
@@ -1604,27 +1618,34 @@ static int nl80211_dump_wiphy(struct sk_buff *skb, struct netlink_callback *cb)
                                 idx--;
                                 break;
                         }
-                } while (cb->args[1] > 0);
+                } while (state->split_start > 0);
                 break;
         }
         rtnl_unlock();
 
-        cb->args[0] = idx;
+        state->start = idx;
 
         return skb->len;
 }
 
+static int nl80211_dump_wiphy_done(struct netlink_callback *cb)
+{
+        kfree((void *)cb->args[0]);
+        return 0;
+}
+
 static int nl80211_get_wiphy(struct sk_buff *skb, struct genl_info *info)
 {
         struct sk_buff *msg;
         struct cfg80211_registered_device *dev = info->user_ptr[0];
+        struct nl80211_dump_wiphy_state state = {};
 
         msg = nlmsg_new(4096, GFP_KERNEL);
         if (!msg)
                 return -ENOMEM;
 
         if (nl80211_send_wiphy(dev, msg, info->snd_portid, info->snd_seq, 0,
-                               false, NULL, NULL, NULL) < 0) {
+                               &state) < 0) {
                 nlmsg_free(msg);
                 return -ENOBUFS;
         }
@@ -8418,6 +8439,7 @@ static struct genl_ops nl80211_ops[] = {
                 .cmd = NL80211_CMD_GET_WIPHY,
                 .doit = nl80211_get_wiphy,
                 .dumpit = nl80211_dump_wiphy,
+                .done = nl80211_dump_wiphy_done,
                 .policy = nl80211_policy,
                 /* can be retrieved by unprivileged users */
                 .internal_flags = NL80211_FLAG_NEED_WIPHY |
@@ -9038,13 +9060,13 @@ static struct genl_multicast_group nl80211_regulatory_mcgrp = {
 void nl80211_notify_dev_rename(struct cfg80211_registered_device *rdev)
 {
         struct sk_buff *msg;
+        struct nl80211_dump_wiphy_state state = {};
 
         msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
         if (!msg)
                 return;
 
-        if (nl80211_send_wiphy(rdev, msg, 0, 0, 0,
-                               false, NULL, NULL, NULL) < 0) {
+        if (nl80211_send_wiphy(rdev, msg, 0, 0, 0, &state) < 0) {
                 nlmsg_free(msg);
                 return;
         }