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| author | Al Viro <viro@zeniv.linux.org.uk> | 2014-10-08 23:44:00 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-11-14 08:47:55 -0800 |
| commit | 0af0e1dba97dc53b9f14795ca49b0b1b24aa0ce1 (patch) | |
| tree | d8a1ca49e5301909334f00853ebb23091a84dd77 /drivers/net | |
| parent | 5f73dee2222e4b602c88419a19dd02ef896513f8 (diff) | |
| download | linux-3.10-0af0e1dba97dc53b9f14795ca49b0b1b24aa0ce1.tar.gz linux-3.10-0af0e1dba97dc53b9f14795ca49b0b1b24aa0ce1.tar.bz2 linux-3.10-0af0e1dba97dc53b9f14795ca49b0b1b24aa0ce1.zip | |
fix misuses of f_count() in ppp and netlink
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 <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/net')
| -rw-r--r-- | drivers/net/ppp/ppp_generic.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 72ff14b811c..5a1897d86e9 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -601,7 +601,7 @@ 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 |