diff options
| author | Dmitry Vyukov <dvyukov@google.com> | 2017-03-04 15:46:12 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-12-20 12:07:26 +0300 |
| commit | 2a47e7de0822ec4794c6a44d8a43c66c49f4d355 (patch) | |
| tree | 73a23ac28de6767774b8bfcc35b0ab7f5939992c | |
| parent | 70f450fc8610464d4ac2274b403b8b15797c27af (diff) | |
| download | linux-2a47e7de0822ec4794c6a44d8a43c66c49f4d355.tar.xz | |
tty: fix data race in tty_ldisc_ref_wait()
[ Upstream commit a4a3e061149f09c075f108b6f1cf04d9739a6bc2 ]
tty_ldisc_ref_wait() checks tty->ldisc under tty->ldisc_sem.
But if ldisc==NULL it releases them sem and reloads
tty->ldisc without holding the sem. This is wrong and
can lead to returning non-NULL ldisc without protection.
Don't reload tty->ldisc second time.
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Cc: syzkaller@googlegroups.com
Cc: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index c3956ca022e4..b0500a0a87b8 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -271,10 +271,13 @@ const struct file_operations tty_ldiscs_proc_fops = { struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) { + struct tty_ldisc *ld; + ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); - if (!tty->ldisc) + ld = tty->ldisc; + if (!ld) ldsem_up_read(&tty->ldisc_sem); - return tty->ldisc; + return ld; } EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |