3.16.7-ckt2 -stable review patch. If anyone has any objections, please let me
know.
------------------
From: Al Viro <v...@zeniv.linux.org.uk>
commit 24dff96a37a2ca319e75a74d3929b2de22447ca6 upstream.
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.
Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Luis Henriques <luis.henriq...@canonical.com>
---
drivers/net/ppp/ppp_generic.c | 2 +-
net/netlink/af_netlink.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index d5b77ef3a210..a75a411b1c27 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -594,7 +594,7 @@ static long ppp_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
if (file == ppp->owner)
ppp_shutdown_interface(ppp);
}
- if (atomic_long_read(&file->f_count) <= 2) {
+ if (atomic_long_read(&file->f_count) < 2) {
ppp_release(NULL, file);
err = 0;
} else
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 48fc607a211e..d158e1c888d8 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -707,7 +707,7 @@ 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;
--
2.1.0
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
