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| author | Peter Hurley <peter@hurleysoftware.com> | 2016-01-10 22:40:55 -0800 |
|---|---|---|
| committer | Simon Shields <keepcalm444@gmail.com> | 2016-03-12 23:11:21 +1100 |
| commit | d3819b76e827ba7e4095657397e5aad2382b8724 (patch) | |
| tree | 960b29978a4f2955ee2e550f936950e96f54862b | |
| parent | 0a7a34f29e714624c5de103e82d4bb18be88b7dc (diff) | |
| download | kernel_samsung_smdk4412-d3819b76e827ba7e4095657397e5aad2382b8724.zip kernel_samsung_smdk4412-d3819b76e827ba7e4095657397e5aad2382b8724.tar.gz kernel_samsung_smdk4412-d3819b76e827ba7e4095657397e5aad2382b8724.tar.bz2 | |
tty: Fix unsafe ldisc reference via ioctl(TIOCGETD)
ioctl(TIOCGETD) retrieves the line discipline id directly from the
ldisc because the line discipline id (c_line) in termios is untrustworthy;
userspace may have set termios via ioctl(TCSETS*) without actually
changing the line discipline via ioctl(TIOCSETD).
However, directly accessing the current ldisc via tty->ldisc is
unsafe; the ldisc ptr dereferenced may be stale if the line discipline
is changing via ioctl(TIOCSETD) or hangup.
Wait for the line discipline reference (just like read() or write())
to retrieve the "current" line discipline id.
Change-Id: I7dae813721d4631d84a7d48b7b908e3bc40617cb
Cc: <stable@vger.kernel.org>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_io.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index cf32a5c..cff688b 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -2447,6 +2447,28 @@ static int tiocsetd(struct tty_struct *tty, int __user *p) } /** + * tiocgetd - get line discipline + * @tty: tty device + * @p: pointer to user data + * + * Retrieves the line discipline id directly from the ldisc. + * + * Locking: waits for ldisc reference (in case the line discipline + * is changing or the tty is being hungup) + */ + +static int tiocgetd(struct tty_struct *tty, int __user *p) +{ + struct tty_ldisc *ld; + int ret; + + ld = tty_ldisc_ref_wait(tty); + ret = put_user(ld->ops->num, p); + tty_ldisc_deref(ld); + return ret; +} + +/** * send_break - performed time break * @tty: device to break on * @duration: timeout in mS @@ -2656,7 +2678,7 @@ long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case TIOCGSID: return tiocgsid(tty, real_tty, p); case TIOCGETD: - return put_user(tty->ldisc->ops->num, (int __user *)p); + return tiocgetd(tty, p); case TIOCSETD: return tiocsetd(tty, p); case TIOCVHANGUP: |