path: root/drivers/net/ppp/ppp_generic.c
diff options
authorAl Viro <viro@zeniv.linux.org.uk>2014-10-08 23:44:00 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-10-09 02:39:17 -0400
commit24dff96a37a2ca319e75a74d3929b2de22447ca6 (patch)
treec6919d9ff42dd0b87c7db90cacfb7631507f50be /drivers/net/ppp/ppp_generic.c
parentncpfs: use list_for_each_entry() for d_subdirs walk (diff)
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 'drivers/net/ppp/ppp_generic.c')
1 files changed, 1 insertions, 1 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)
- if (atomic_long_read(&file->f_count) <= 2) {
+ if (atomic_long_read(&file->f_count) < 2) {
ppp_release(NULL, file);
err = 0;
} else