linux-stable.git/drivers/tty, branch v5.9.14

tty: Fix ->session locking

2020-12-11T12:22:04+00:00

commit c8bcd9c5be24fb9e6132e97da5a35e55a83e36b9 upstream.

Currently, locking of ->session is very inconsistent; most places
protect it using the legacy tty mutex, but disassociate_ctty(),
__do_SAK(), tiocspgrp() and tiocgsid() don't.
Two of the writers hold the ctrl_lock (because they already need it for
->pgrp), but __proc_set_tty() doesn't do that yet.

On a PREEMPT=y system, an unprivileged user can theoretically abuse
this broken locking to read 4 bytes of freed memory via TIOCGSID if
tiocgsid() is preempted long enough at the right point. (Other things
might also go wrong, especially if root-only ioctls are involved; I'm
not sure about that.)

Change the locking on ->session such that:

 - tty_lock() is held by all writers: By making disassociate_ctty()
   hold it. This should be fine because the same lock can already be
   taken through the call to tty_vhangup_session().
   The tricky part is that we need to shorten the area covered by
   siglock to be able to take tty_lock() without ugly retry logic; as
   far as I can tell, this should be fine, since nothing in the
   signal_struct is touched in the `if (tty)` branch.
 - ctrl_lock is held by all writers: By changing __proc_set_tty() to
   hold the lock a little longer.
 - All readers that aren't holding tty_lock() hold ctrl_lock: By
   adding locking to tiocgsid() and __do_SAK(), and expanding the area
   covered by ctrl_lock in tiocspgrp().

Cc: stable@kernel.org
Signed-off-by: Jann Horn 
Reviewed-by: Jiri Slaby 
Signed-off-by: Greg Kroah-Hartman

tty: Fix ->pgrp locking in tiocspgrp()

2020-12-11T12:22:04+00:00

commit 54ffccbf053b5b6ca4f6e45094b942fab92a25fc upstream.

tiocspgrp() takes two tty_struct pointers: One to the tty that userspace
passed to ioctl() (`tty`) and one to the TTY being changed (`real_tty`).
These pointers are different when ioctl() is called with a master fd.

To properly lock real_tty->pgrp, we must take real_tty->ctrl_lock.

This bug makes it possible for racing ioctl(TIOCSPGRP, ...) calls on
both sides of a PTY pair to corrupt the refcount of `struct pid`,
leading to use-after-free errors.

Fixes: 47f86834bbd4 ("redo locking of tty->pgrp")
CC: stable@kernel.org
Signed-off-by: Jann Horn 
Reviewed-by: Jiri Slaby 
Signed-off-by: Greg Kroah-Hartman

serial: ar933x_uart: disable clk on error handling path in probe

2020-11-24T12:39:10+00:00

commit 425af483523b76bc78e14674a430579d38b2a593 upstream.

ar933x_uart_probe() does not invoke clk_disable_unprepare()
on one error handling path. This patch fixes that.

Fixes: 9be1064fe524 ("serial: ar933x_uart: add RS485 support")
Reported-by: Hulk Robot 
Signed-off-by: Zheng Zengkai 
Link: https://lore.kernel.org/r/20201111124426.42638-1-zhengzengkai@huawei.com
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

tty: serial: imx: keep console clocks always on

2020-11-24T12:39:08+00:00

commit e67c139c488e84e7eae6c333231e791f0e89b3fb upstream.

For below code, there has chance to cause deadlock in SMP system:
Thread 1:
clk_enable_lock();
pr_info("debug message");
clk_enable_unlock();

Thread 2:
imx_uart_console_write()
	clk_enable()
		clk_enable_lock();

Thread 1:
Acuired clk enable_lock -> printk -> console_trylock_spinning
Thread 2:
console_unlock() -> imx_uart_console_write -> clk_disable -> Acquite clk enable_lock

So the patch is to keep console port clocks always on like
other console drivers.

Fixes: 1cf93e0d5488 ("serial: imx: remove the uart_console() check")
Acked-by: Uwe Kleine-König 
Signed-off-by: Fugang Duan 
Link: https://lore.kernel.org/r/20201111025136.29818-1-fugang.duan@nxp.com
Cc: stable 
[fix up build warning - gregkh]
Signed-off-by: Greg Kroah-Hartman

tty: serial: imx: fix potential deadlock

2020-11-24T12:39:08+00:00

commit 33f16855dcb973f745c51882d0e286601ff3be2b upstream.

Enabling the lock dependency validator has revealed
that the way spinlocks are used in the IMX serial
port could result in a deadlock.

Specifically, imx_uart_int() acquires a spinlock
without disabling the interrupts, meaning that another
interrupt could come along and try to acquire the same
spinlock, potentially causing the two to wait for each
other indefinitely.

Use spin_lock_irqsave() instead to disable interrupts
upon acquisition of the spinlock.

Fixes: c974991d2620 ("tty:serial:imx: use spin_lock instead of spin_lock_irqsave in isr")
Reviewed-by: Uwe Kleine-König 
Signed-off-by: Sam Nobs 
Link: https://lore.kernel.org/r/1604955006-9363-1-git-send-email-samuel.nobs@taitradio.com
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

serial: txx9: add missing platform_driver_unregister() on error in serial_txx9_init

2020-11-10T11:39:09+00:00

commit 0c5fc92622ed5531ff324b20f014e9e3092f0187 upstream.

Add the missing platform_driver_unregister() before return
from serial_txx9_init in the error handling case when failed
to register serial_txx9_pci_driver with macro ENABLE_SERIAL_TXX9_PCI
defined.

Fixes: ab4382d27412 ("tty: move drivers/serial/ to drivers/tty/serial/")
Signed-off-by: Qinglang Miao 
Link: https://lore.kernel.org/r/20201103084942.109076-1-miaoqinglang@huawei.com
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

serial: 8250_mtk: Fix uart_get_baud_rate warning

2020-11-10T11:39:09+00:00

commit 912ab37c798770f21b182d656937072b58553378 upstream.

Mediatek 8250 port supports speed higher than uartclk / 16. If the baud
rates in both the new and the old termios setting are higher than
uartclk / 16, the WARN_ON in uart_get_baud_rate() will be triggered.
Passing NULL as the old termios so uart_get_baud_rate() will use
uartclk / 16 - 1 as the new baud rate which will be replaced by the
original baud rate later by tty_termios_encode_baud_rate() in
mtk8250_set_termios().

Fixes: 551e553f0d4a ("serial: 8250_mtk: Fix high-speed baud rates clamping")
Signed-off-by: Claire Chang 
Link: https://lore.kernel.org/r/20201102120749.374458-1-tientzu@chromium.org
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

tty: fix crash in release_tty if tty->port is not set

2020-11-10T11:39:07+00:00

commit 4466d6d2f80c1193e0845d110277c56da77a6418 upstream.

Commit 2ae0b31e0face ("tty: don't crash in tty_init_dev when missing
tty_port") didn't fully prevent the crash as the cleanup path in
tty_init_dev() calls release_tty() which dereferences tty->port
without checking it for non-null.

Add tty->port checks to release_tty to avoid the kernel crash.

Fixes: 2ae0b31e0face ("tty: don't crash in tty_init_dev when missing tty_port")
Signed-off-by: Matthias Reichl 
Link: https://lore.kernel.org/r/20201105123432.4448-1-hias@horus.com
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

tty: serial: imx: enable earlycon by default if IMX_SERIAL_CONSOLE is enabled

2020-11-10T11:39:07+00:00

commit 427627a23c3e86e31113f9db9bfdca41698a0ee5 upstream.

Since 699cc4dfd140 (tty: serial: imx: add imx earlycon driver), the earlycon
part of imx serial is a separate driver and isn't necessarily enabled anymore
when the console is enabled. This causes users to loose the earlycon
functionality when upgrading their kenrel configuration via oldconfig.

Enable earlycon by default when IMX_SERIAL_CONSOLE is enabled.

Fixes: 699cc4dfd140 (tty: serial: imx: add imx earlycon driver)
Reviewed-by: Fabio Estevam 
Reviewed-by: Fugang Duan 
Signed-off-by: Lucas Stach 
Link: https://lore.kernel.org/r/20201105204026.1818219-1-l.stach@pengutronix.de
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

vt: Disable KD_FONT_OP_COPY

2020-11-10T11:39:07+00:00

commit 3c4e0dff2095c579b142d5a0693257f1c58b4804 upstream.

It's buggy:

On Fri, Nov 06, 2020 at 10:30:08PM +0800, Minh Yuan wrote:
> We recently discovered a slab-out-of-bounds read in fbcon in the latest
> kernel ( v5.10-rc2 for now ).  The root cause of this vulnerability is that
> "fbcon_do_set_font" did not handle "vc->vc_font.data" and
> "vc->vc_font.height" correctly, and the patch
>  for VT_RESIZEX can't handle this
> issue.
>
> Specifically, we use KD_FONT_OP_SET to set a small font.data for tty6, and
> use  KD_FONT_OP_SET again to set a large font.height for tty1. After that,
> we use KD_FONT_OP_COPY to assign tty6's vc_font.data to tty1's vc_font.data
> in "fbcon_do_set_font", while tty1 retains the original larger
> height. Obviously, this will cause an out-of-bounds read, because we can
> access a smaller vc_font.data with a larger vc_font.height.

Further there was only one user ever.
- Android's loadfont, busybox and console-tools only ever use OP_GET
  and OP_SET
- fbset documentation only mentions the kernel cmdline font: option,
  not anything else.
- systemd used OP_COPY before release 232 published in Nov 2016

Now unfortunately the crucial report seems to have gone down with
gmane, and the commit message doesn't say much. But the pull request
hints at OP_COPY being broken

https://github.com/systemd/systemd/pull/3651

So in other words, this never worked, and the only project which
foolishly every tried to use it, realized that rather quickly too.

Instead of trying to fix security issues here on dead code by adding
missing checks, fix the entire thing by removing the functionality.

Note that systemd code using the OP_COPY function ignored the return
value, so it doesn't matter what we're doing here really - just in
case a lone server somewhere happens to be extremely unlucky and
running an affected old version of systemd. The relevant code from
font_copy_to_all_vcs() in systemd was:

	/* copy font from active VT, where the font was uploaded to */
	cfo.op = KD_FONT_OP_COPY;
	cfo.height = vcs.v_active-1; /* tty1 == index 0 */
	(void) ioctl(vcfd, KDFONTOP, &cfo);

Note this just disables the ioctl, garbage collecting the now unused
callbacks is left for -next.

v2: Tetsuo found the old mail, which allowed me to find it on another
archive. Add the link too.

Acked-by: Peilin Ye 
Reported-by: Minh Yuan 
References: https://lists.freedesktop.org/archives/systemd-devel/2016-June/036935.html
References: https://github.com/systemd/systemd/pull/3651
Cc: Greg KH 
Cc: Peilin Ye 
Cc: Tetsuo Handa 
Signed-off-by: Daniel Vetter 
Link: https://lore.kernel.org/r/20201108153806.3140315-1-daniel.vetter@ffwll.ch
Signed-off-by: Greg Kroah-Hartman