linux-stable.git/drivers/tty/tty_io.c, branch linux-3.2.y Linux kernel stable tree tty: Fix unsafe ldisc reference via ioctl(TIOCGETD) 2016-02-27T14:28:44+00:00 Peter Hurley peter@hurleysoftware.com 2016-01-11T06:40:55+00:00 710dbb61210c0546cd1bfd9ebd0ad29207202d26 commit 5c17c861a357e9458001f021a7afa7aab9937439 upstream. 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. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 5c17c861a357e9458001f021a7afa7aab9937439 upstream.

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.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
drivers/tty: require read access for controlling terminal 2015-11-17T15:54:42+00:00 Jann Horn jann@thejh.net 2015-10-04T17:29:12+00:00 db0054fe613b21cd65c1609680cc47c520760044 commit 0c55627167870255158db1cde0d28366f91c8872 upstream. This is mostly a hardening fix, given that write-only access to other users' ttys is usually only given through setgid tty executables. Signed-off-by: Jann Horn <jann@thejh.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: - __proc_set_tty() also takes a task_struct pointer] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 0c55627167870255158db1cde0d28366f91c8872 upstream.

This is mostly a hardening fix, given that write-only access to other
users' ttys is usually only given through setgid tty executables.

Signed-off-by: Jann Horn <jann@thejh.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2:
 - __proc_set_tty() also takes a task_struct pointer]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
tty: fix up atime/mtime mess, take four 2015-05-09T22:16:24+00:00 Jiri Slaby jslaby@suse.cz 2015-02-27T17:40:31+00:00 52220b428973e533ba074a818d65aee1f78a2618 commit f0bf0bd07943bfde8f5ac39a32664810a379c7d3 upstream. This problem was taken care of three times already in * b0de59b5733d18b0d1974a060860a8b5c1b36a2e (TTY: do not update atime/mtime on read/write), * 37b7f3c76595e23257f61bd80b223de8658617ee (TTY: fix atime/mtime regression), and * b0b885657b6c8ef63a46bc9299b2a7715d19acde (tty: fix up atime/mtime mess, take three) But it still misses one point. As John Paul correctly points out, we do not care about setting date. If somebody ever changes wall time backwards (by mistake for example), tty timestamps are never updated until the original wall time passes. So check the absolute difference of times and if it large than "8 seconds or so", always update the time. That means we will update immediatelly when changing time. Ergo, CAP_SYS_TIME can foul the check, but it was always that way. Thanks John for serving me this so nicely debugged. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Reported-by: John Paul Perry <john_paul.perry@alcatel-lucent.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit f0bf0bd07943bfde8f5ac39a32664810a379c7d3 upstream.

This problem was taken care of three times already in
* b0de59b5733d18b0d1974a060860a8b5c1b36a2e (TTY: do not update
  atime/mtime on read/write),
* 37b7f3c76595e23257f61bd80b223de8658617ee (TTY: fix atime/mtime
  regression), and
* b0b885657b6c8ef63a46bc9299b2a7715d19acde (tty: fix up atime/mtime
  mess, take three)

But it still misses one point. As John Paul correctly points out, we
do not care about setting date. If somebody ever changes wall
time backwards (by mistake for example), tty timestamps are never
updated until the original wall time passes.

So check the absolute difference of times and if it large than "8
seconds or so", always update the time. That means we will update
immediatelly when changing time. Ergo, CAP_SYS_TIME can foul the
check, but it was always that way.

Thanks John for serving me this so nicely debugged.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Reported-by: John Paul Perry <john_paul.perry@alcatel-lucent.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
tty: Fix high cpu load if tty is unreleaseable 2014-12-14T16:23:55+00:00 Peter Hurley peter@hurleysoftware.com 2014-10-16T17:51:30+00:00 069347b245ac0afe052f68e7f5ea734207f826f4 commit 37b164578826406a173ca7c20d9ba7430134d23e upstream. Kernel oops can cause the tty to be unreleaseable (for example, if n_tty_read() crashes while on the read_wait queue). This will cause tty_release() to endlessly loop without sleeping. Use a killable sleep timeout which grows by 2n+1 jiffies over the interval [0, 120 secs.) and then jumps to forever (but still killable). NB: killable just allows for the task to be rewoken manually, not to be terminated. Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 37b164578826406a173ca7c20d9ba7430134d23e upstream.

Kernel oops can cause the tty to be unreleaseable (for example, if
n_tty_read() crashes while on the read_wait queue). This will cause
tty_release() to endlessly loop without sleeping.

Use a killable sleep timeout which grows by 2n+1 jiffies over the interval
[0, 120 secs.) and then jumps to forever (but still killable).

NB: killable just allows for the task to be rewoken manually, not
to be terminated.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
tty: Set correct tty name in 'active' sysfs attribute 2014-04-30T15:23:20+00:00 Hannes Reinecke hare@suse.de 2014-02-27T11:30:51+00:00 66f328f3931d53a33c10c1003133bba1a2f5cb00 commit 723abd87f6e536f1353c8f64f621520bc29523a3 upstream. The 'active' sysfs attribute should refer to the currently active tty devices the console is running on, not the currently active console. The console structure doesn't refer to any device in sysfs, only the tty the console is running on has. So we need to print out the tty names in 'active', not the console names. There is one special-case, which is tty0. If the console is directed to it, we want 'tty0' to show up in the file, so user-space knows that the messages get forwarded to the active VT. The ->device() callback would resolve tty0, though. Hence, treat it special and don't call into the VT layer to resolve it (plymouth is known to depend on it). Cc: Lennart Poettering <lennart@poettering.net> Cc: Kay Sievers <kay@vrfy.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Werner Fink <werner@suse.de> Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> [bwh: Backported to 3.2: no TTY_DRIVER_UNNUMBERED_NODE case in tty_line_name()] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 723abd87f6e536f1353c8f64f621520bc29523a3 upstream.

The 'active' sysfs attribute should refer to the currently active tty
devices the console is running on, not the currently active console. The
console structure doesn't refer to any device in sysfs, only the tty the
console is running on has. So we need to print out the tty names in
'active', not the console names.

There is one special-case, which is tty0. If the console is directed to
it, we want 'tty0' to show up in the file, so user-space knows that the
messages get forwarded to the active VT. The ->device() callback would
resolve tty0, though. Hence, treat it special and don't call into the VT
layer to resolve it (plymouth is known to depend on it).

Cc: Lennart Poettering <lennart@poettering.net>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Werner Fink <werner@suse.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: no TTY_DRIVER_UNNUMBERED_NODE case in tty_line_name()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
tty: fix up atime/mtime mess, take three 2013-05-13T14:02:32+00:00 Linus Torvalds torvalds@linux-foundation.org 2013-05-01T14:32:21+00:00 cd945654552d978b84c0825c7206b2d0667a1272 commit b0b885657b6c8ef63a46bc9299b2a7715d19acde upstream. We first tried to avoid updating atime/mtime entirely (commit b0de59b5733d: "TTY: do not update atime/mtime on read/write"), and then limited it to only update it occasionally (commit 37b7f3c76595: "TTY: fix atime/mtime regression"), but it turns out that this was both insufficient and overkill. It was insufficient because we let people attach to the shared ptmx node to see activity without even reading atime/mtime, and it was overkill because the "only once a minute" means that you can't really tell an idle person from an active one with 'w'. So this tries to fix the problem properly. It marks the shared ptmx node as un-notifiable, and it lowers the "only once a minute" to a few seconds instead - still long enough that you can't time individual keystrokes, but short enough that you can tell whether somebody is active or not. Reported-by: Simon Kirby <sim@hostway.ca> Acked-by: Jiri Slaby <jslaby@suse.cz> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit b0b885657b6c8ef63a46bc9299b2a7715d19acde upstream.

We first tried to avoid updating atime/mtime entirely (commit
b0de59b5733d: "TTY: do not update atime/mtime on read/write"), and then
limited it to only update it occasionally (commit 37b7f3c76595: "TTY:
fix atime/mtime regression"), but it turns out that this was both
insufficient and overkill.

It was insufficient because we let people attach to the shared ptmx node
to see activity without even reading atime/mtime, and it was overkill
because the "only once a minute" means that you can't really tell an
idle person from an active one with 'w'.

So this tries to fix the problem properly.  It marks the shared ptmx
node as un-notifiable, and it lowers the "only once a minute" to a few
seconds instead - still long enough that you can't time individual
keystrokes, but short enough that you can tell whether somebody is
active or not.

Reported-by: Simon Kirby <sim@hostway.ca>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
TTY: fix atime/mtime regression 2013-05-13T14:02:31+00:00 Jiri Slaby jslaby@suse.cz 2013-04-26T11:48:53+00:00 0b28f5865ef23d2bcee122d75b4aea1e2f052624 commit 37b7f3c76595e23257f61bd80b223de8658617ee upstream. In commit b0de59b5733d ("TTY: do not update atime/mtime on read/write") we removed timestamps from tty inodes to fix a security issue and waited if something breaks. Well, 'w', the utility to find out logged users and their inactivity time broke. It shows that users are inactive since the time they logged in. To revert to the old behaviour while still preventing attackers to guess the password length, we update the timestamps in one-minute intervals by this patch. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [bwh: For 3.2, use Greg's backported version] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 37b7f3c76595e23257f61bd80b223de8658617ee upstream.

In commit b0de59b5733d ("TTY: do not update atime/mtime on read/write")
we removed timestamps from tty inodes to fix a security issue and waited
if something breaks.  Well, 'w', the utility to find out logged users
and their inactivity time broke.  It shows that users are inactive since
the time they logged in.

To revert to the old behaviour while still preventing attackers to
guess the password length, we update the timestamps in one-minute
intervals by this patch.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: For 3.2, use Greg's backported version]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
TTY: do not update atime/mtime on read/write 2013-05-13T14:02:31+00:00 Jiri Slaby jslaby@suse.cz 2013-02-15T14:25:05+00:00 c29ad805df8c54a9f5d74c66bf5d4a2d449bd99a commit b0de59b5733d18b0d1974a060860a8b5c1b36a2e upstream. On http://vladz.devzero.fr/013_ptmx-timing.php, we can see how to find out length of a password using timestamps of /dev/ptmx. It is documented in "Timing Analysis of Keystrokes and Timing Attacks on SSH". To avoid that problem, do not update time when reading from/writing to a TTY. I am afraid of regressions as this is a behavior we have since 0.97 and apps may expect the time to be current, e.g. for monitoring whether there was a change on the TTY. Now, there is no change. So this would better have a lot of testing before it goes upstream. References: CVE-2013-0160 Signed-off-by: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit b0de59b5733d18b0d1974a060860a8b5c1b36a2e upstream.

On http://vladz.devzero.fr/013_ptmx-timing.php, we can see how to find
out length of a password using timestamps of /dev/ptmx. It is
documented in "Timing Analysis of Keystrokes and Timing Attacks on
SSH". To avoid that problem, do not update time when reading
from/writing to a TTY.

I am afraid of regressions as this is a behavior we have since 0.97
and apps may expect the time to be current, e.g. for monitoring
whether there was a change on the TTY. Now, there is no change. So
this would better have a lot of testing before it goes upstream.

References: CVE-2013-0160

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Merge branch 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty 2011-10-26T13:11:09+00:00 Linus Torvalds torvalds@linux-foundation.org 2011-10-26T13:11:09+00:00 efb8d21b2c6db3497655cc6a033ae8a9883e4063 * 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (79 commits) TTY: serial_core: Fix crash if DCD drop during suspend tty/serial: atmel_serial: bootconsole removed from auto-enumerates Revert "TTY: call tty_driver_lookup_tty unconditionally" tty/serial: atmel_serial: add device tree support tty/serial: atmel_serial: auto-enumerate ports tty/serial: atmel_serial: whitespace and braces modifications tty/serial: atmel_serial: change platform_data variable name tty/serial: RS485 bindings for device tree TTY: call tty_driver_lookup_tty unconditionally TTY: pty, release tty in all ptmx_open fail paths TTY: make tty_add_file non-failing TTY: drop driver reference in tty_open fail path 8250_pci: Fix kernel panic when pch_uart is disabled h8300: drivers/serial/Kconfig was moved parport_pc: release IO region properly if unsupported ITE887x card is found tty: Support compat_ioctl get/set termios_locked hvc_console: display printk messages on console. TTY: snyclinkmp: forever loop in tx_load_dma_buffer() tty/n_gsm: avoid fifo overflow in gsm_dlci_data_output tty/n_gsm: fix a bug in gsm_dlci_data_output (adaption = 2 case) ... Fix up Conflicts in: - drivers/tty/serial/8250_pci.c Trivial conflict with removed duplicate device ID - drivers/tty/serial/atmel_serial.c Annoying silly conflict between "specify the port num via platform_data" and other changes to atmel_console_init 
* 'tty-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (79 commits)
  TTY: serial_core: Fix crash if DCD drop during suspend
  tty/serial: atmel_serial: bootconsole removed from auto-enumerates
  Revert "TTY: call tty_driver_lookup_tty unconditionally"
  tty/serial: atmel_serial: add device tree support
  tty/serial: atmel_serial: auto-enumerate ports
  tty/serial: atmel_serial: whitespace and braces modifications
  tty/serial: atmel_serial: change platform_data variable name
  tty/serial: RS485 bindings for device tree
  TTY: call tty_driver_lookup_tty unconditionally
  TTY: pty, release tty in all ptmx_open fail paths
  TTY: make tty_add_file non-failing
  TTY: drop driver reference in tty_open fail path
  8250_pci: Fix kernel panic when pch_uart is disabled
  h8300: drivers/serial/Kconfig was moved
  parport_pc: release IO region properly if unsupported ITE887x card is found
  tty: Support compat_ioctl get/set termios_locked
  hvc_console: display printk messages on console.
  TTY: snyclinkmp: forever loop in tx_load_dma_buffer()
  tty/n_gsm: avoid fifo overflow in gsm_dlci_data_output
  tty/n_gsm: fix a bug in gsm_dlci_data_output (adaption = 2 case)
  ...

Fix up Conflicts in:
 - drivers/tty/serial/8250_pci.c
	Trivial conflict with removed duplicate device ID
 - drivers/tty/serial/atmel_serial.c
	Annoying silly conflict between "specify the port num via
	platform_data" and other changes to atmel_console_init
Revert "TTY: call tty_driver_lookup_tty unconditionally" 2011-10-19T15:33:21+00:00 Greg Kroah-Hartman gregkh@suse.de 2011-10-19T15:33:21+00:00 a0340703981baa6cc1e9c7c768095a0a4e718daf This reverts commit 631180aca723cb92e128fdac5fd144e913ca84e5. It caused problems when /dev/tty is a pty: https://lkml.org/lkml/2011/10/12/401 Cc: Jiri Slaby <jslaby@suse.cz> Cc: stable <stable@vger.kernel.org> Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com> Cc: Alan Cox <alan@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> 
This reverts commit 631180aca723cb92e128fdac5fd144e913ca84e5.

It caused problems when /dev/tty is a pty:
	https://lkml.org/lkml/2011/10/12/401

Cc: Jiri Slaby <jslaby@suse.cz>
Cc: stable <stable@vger.kernel.org>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>