From: Johannes Berg <johannes.berg@xxxxxxxxx>
Since my commit 3713b4e364, nl80211_dump_wiphy() uses the global
nl80211_fam.attrbuf for parsing the incoming data. This wouldn't
be a problem if it only did so on the first dump iteration which
is locked against other commands in generic netlink, but due to
space constraints in cb->args (the needed state doesn't fit) I
decided to always parse the original message. That's racy though
since nl80211_fam.attrbuf could be used by some other parsing in
generic netlink concurrently.
For now, fix this by allocating a separate parse buffer (it's a
bit too big for the stack, currently 1448 bytes on 64-bit). For
-next, I'll change the code to parse into the global buffer in
the first round only and then allocate a smaller buffer to keep
the state in cb->args.
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
Let me know if you want to apply this directly, otherwise I'll send it
on its way to John.
net/wireless/nl80211.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index d5aed3b..b14b7e3 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -1564,12 +1564,17 @@ static int nl80211_dump_wiphy(struct sk_buff *skb, struct netlink_callback *cb)
struct cfg80211_registered_device *dev;
s64 filter_wiphy = -1;
bool split = false;
- struct nlattr **tb = nl80211_fam.attrbuf;
+ 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;
+
mutex_lock(&cfg80211_mutex);
res = nlmsg_parse(cb->nlh, GENL_HDRLEN + nl80211_fam.hdrsize,
- tb, nl80211_fam.maxattr, nl80211_policy);
+ tb, NL80211_ATTR_MAX, nl80211_policy);
if (res == 0) {
split = tb[NL80211_ATTR_SPLIT_WIPHY_DUMP];
if (tb[NL80211_ATTR_WIPHY])
@@ -1583,6 +1588,7 @@ static int nl80211_dump_wiphy(struct sk_buff *skb, struct netlink_callback *cb)
netdev = dev_get_by_index(sock_net(skb->sk), ifidx);
if (!netdev) {
mutex_unlock(&cfg80211_mutex);
+ kfree(tb);
return -ENODEV;
}
if (netdev->ieee80211_ptr) {
@@ -1593,6 +1599,7 @@ static int nl80211_dump_wiphy(struct sk_buff *skb, struct netlink_callback *cb)
dev_put(netdev);
}
}
+ kfree(tb);
list_for_each_entry(dev, &cfg80211_rdev_list, list) {
if (!net_eq(wiphy_net(&dev->wiphy), sock_net(skb->sk)))
--
1.8.0
--
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