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authorAl Viro <viro@zeniv.linux.org.uk>2014-10-09 07:44:00 +0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-10-09 10:39:17 +0400
commit24dff96a37a2ca319e75a74d3929b2de22447ca6 (patch)
treec6919d9ff42dd0b87c7db90cacfb7631507f50be /net/netlink
parent821cc3070ff54e39ab6624c843f1905d737d9ac0 (diff)
downloadlinux-24dff96a37a2ca319e75a74d3929b2de22447ca6.tar.xz
fix misuses of f_count() in ppp and netlink
we used to check for "nobody else could start doing anything with that opened file" by checking that refcount was 2 or less - one for descriptor table and one we'd acquired in fget() on the way to wherever we are. That was race-prone (somebody else might have had a reference to descriptor table and do fget() just as we'd been checking) and it had become flat-out incorrect back when we switched to fget_light() on those codepaths - unlike fget(), it doesn't grab an extra reference unless the descriptor table is shared. The same change allowed a race-free check, though - we are safe exactly when refcount is less than 2. It was a long time ago; pre-2.6.12 for ioctl() (the codepath leading to ppp one) and 2.6.17 for sendmsg() (netlink one). OTOH, netlink hadn't grown that check until 3.9 and ppp used to live in drivers/net, not drivers/net/ppp until 3.1. The bug existed well before that, though, and the same fix used to apply in old location of file. Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/af_netlink.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index c416725d28c4..7a186e74b1b3 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -715,7 +715,7 @@ static int netlink_mmap_sendmsg(struct sock *sk, struct msghdr *msg,
* after validation, the socket and the ring may only be used by a
* single process, otherwise we fall back to copying.
*/
- if (atomic_long_read(&sk->sk_socket->file->f_count) > 2 ||
+ if (atomic_long_read(&sk->sk_socket->file->f_count) > 1 ||
atomic_read(&nlk->mapped) > 1)
excl = false;