path: root/net
diff options
authorJohannes Berg <johannes.berg@intel.com>2013-08-13 09:04:05 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-20 08:43:03 -0700
commitaab4f8d490ef8c184d854d5f630438c10406765c (patch)
treedd06cadc3e41a9744a61d0e94031f3554374744e /net
parentd00ff4f2e5340b4a1fae711c46d804500e4ad7f9 (diff)
genetlink: fix family dump race
commit 58ad436fcf49810aa006016107f494c9ac9013db upstream. When dumping generic netlink families, only the first dump call is locked with genl_lock(), which protects the list of families, and thus subsequent calls can access the data without locking, racing against family addition/removal. This can cause a crash. Fix it - the locking needs to be conditional because the first time around it's already locked. A similar bug was reported to me on an old kernel (3.4.47) but the exact scenario that happened there is no longer possible, on those kernels the first round wasn't locked either. Looking at the current code I found the race described above, which had also existed on the old kernel. Reported-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
1 files changed, 7 insertions, 0 deletions
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 1076fe16b12..ba6e55d1ca4 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -789,6 +789,10 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
struct net *net = sock_net(skb->sk);
int chains_to_skip = cb->args[0];
int fams_to_skip = cb->args[1];
+ bool need_locking = chains_to_skip || fams_to_skip;
+ if (need_locking)
+ genl_lock();
for (i = chains_to_skip; i < GENL_FAM_TAB_SIZE; i++) {
n = 0;
@@ -810,6 +814,9 @@ errout:
cb->args[0] = i;
cb->args[1] = n;
+ if (need_locking)
+ genl_unlock();
return skb->len;