diff options
| author |   Al Viro <viro@zeniv.linux.org.uk> | 2014-10-08 23:44:00 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2014-10-09 02:39:17 -0400 |
| commit | 24dff96a37a2ca319e75a74d3929b2de22447ca6 (patch) | |
| tree | c6919d9ff42dd0b87c7db90cacfb7631507f50be | |
| parent | ncpfs: use list_for_each_entry() for d_subdirs walk (diff) | |
| download | linux-dev-24dff96a37a2ca319e75a74d3929b2de22447ca6.tar.xz linux-dev-24dff96a37a2ca319e75a74d3929b2de22447ca6.zip | |
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>
| -rw-r--r-- | drivers/net/ppp/ppp_generic.c | 2 | ||||
| -rw-r--r-- | 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 fa0d71727894..90c639b0f18d 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 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; |