linux/drivers/tty, branch v5.10

tty: Fix ->session locking

2020-12-04T16:39:58Z

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()

2020-12-04T16:38:48Z

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

2020-11-12T08:41:07Z

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

2020-11-12T08:39:53Z

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

2020-11-12T08:32:49Z

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

Merge tag 'tty-5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2020-11-08T19:28:08Z

Pull tty/serial fixes from Greg KH: "Here are a small number of small tty and serial fixes for some reported problems for the tty core, vt code, and some serial drivers. They include fixes for: - a buggy and obsolete vt font ioctl removal - 8250_mtk serial baudrate runtime warnings - imx serial earlycon build configuration fix - txx9 serial driver error path cleanup issues - tty core fix in release_tty that can be triggered by trying to bind an invalid serial port name to a speakup console device Almost all of these have been in linux-next without any problems, the only one that hasn't, just deletes code :)" * tag 'tty-5.10-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: vt: Disable KD_FONT_OP_COPY tty: fix crash in release_tty if tty->port is not set serial: txx9: add missing platform_driver_unregister() on error in serial_txx9_init tty: serial: imx: enable earlycon by default if IMX_SERIAL_CONSOLE is enabled serial: 8250_mtk: Fix uart_get_baud_rate warning

vt: Disable KD_FONT_OP_COPY

2020-11-08T18:35:06Z

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

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

2020-11-06T16:24:49Z

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

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

2020-11-06T16:24:41Z

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

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

2020-11-06T16:23:49Z

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