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nl80211: fix attrbuf access race by allocating a separate one

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Since my commit 3713b4e364 ("nl80211: allow splitting wiphy
information in dumps"), 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 data in cb->args.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Johannes Berg 2013-06-19 10:09:57 +02:00
parent 795d855d56
commit 3a5a423bb9
1 changed files with 9 additions and 2 deletions
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11
net/wireless/nl80211.c
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@ -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)))