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[PATCH 3.19.y-ckt 32/47] staging/speakup: Use tty_ldisc_ref() for paste kworker

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3.19.8-ckt15 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Peter Hurley <peter@hurleysoftware.com>

commit f4f9edcf9b5289ed96113e79fa65a7bf27ecb096 upstream.

As the function documentation for tty_ldisc_ref_wait() notes, it is
only callable from a tty file_operations routine; otherwise there
is no guarantee the ref won't be NULL.

The key difference with the VT's paste_selection() is that is an ioctl,
where __speakup_paste_selection() is completely async kworker, kicked
off from interrupt context.

Fixes: 28a821c30688 ("Staging: speakup: Update __speakup_paste_selection()
       tty (ab)usage to match vt")
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/staging/speakup/selection.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/speakup/selection.c b/drivers/staging/speakup/selection.c
index 507fc9a..fb6a686 100644
--- a/drivers/staging/speakup/selection.c
+++ b/drivers/staging/speakup/selection.c
@@ -141,7 +141,9 @@ static void __speakup_paste_selection(struct work_struct *work)
 	struct tty_ldisc *ld;
 	DECLARE_WAITQUEUE(wait, current);
 
-	ld = tty_ldisc_ref_wait(tty);
+	ld = tty_ldisc_ref(tty);
+	if (!ld)
+		goto tty_unref;
 	tty_buffer_lock_exclusive(&vc->port);
 
 	add_wait_queue(&vc->paste_wait, &wait);
@@ -161,6 +163,7 @@ static void __speakup_paste_selection(struct work_struct *work)
 
 	tty_buffer_unlock_exclusive(&vc->port);
 	tty_ldisc_deref(ld);
+tty_unref:
 	tty_kref_put(tty);
 }
 
-- 
1.9.1

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[3.19.y-ckt stable] Linux 3.19.8-ckt15 stable review Kamal Mostafa <kamal@canonical.com> - 2016-02-09 23:50 +0100
  [PATCH 3.19.y-ckt 47/47] KEYS: Fix keyring ref leak in join_session_keyring() Kamal Mostafa <kamal@canonical.com> - 2016-02-09 23:50 +0100
  [PATCH 3.19.y-ckt 41/47] perf hists: Fix HISTC_MEM_DCACHELINE width setting Kamal Mostafa <kamal@canonical.com> - 2016-02-09 23:50 +0100
  [PATCH 3.19.y-ckt 11/47] cdc-acm:exclude Samsung phone 04e8:685d Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 10/47] usb: cdc-acm: send zero packet for intel 7260 modem Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 17/47] ALSA: seq: Fix incorrect sanity check at snd_seq_oss_synth_cleanup() Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 35/47] ALSA: dummy: Disable switching timer backend via sysfs Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 34/47] seccomp: always propagate NO_NEW_PRIVS on tsync Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 19/47] USB: serial: ftdi_sio: add support for Yaesu SCU-18 cable Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 23/47] ALSA: usb-audio: Fix TEAC UD-501/UD-503/NT-503 usb delay Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 16/47] USB: serial: option: Adding support for Telit LE922 Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 36/47] drm/vmwgfx: respect 'nomodeset' Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 24/47] ALSA: bebob: Use a signed return type for get_formation_index Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 12/47] usb: hub: do not clear BOS field during reset device Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 09/47] usb: cdc-acm: handle unlinked urb in acm read callback Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 30/47] tty: Fix unsafe ldisc reference via ioctl(TIOCGETD) Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 21/47] USB: option: fix Cinterion AHxx enumeration Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 28/47] powerpc/eeh: Fix PE location code Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 15/47] USB: serial: visor: fix crash on detecting device without write_urbs Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 32/47] staging/speakup: Use tty_ldisc_ref() for paste kworker Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 22/47] ALSA: compress: Disable GET_CODEC_CAPS ioctl for some architectures Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 14/47] USB: visor: fix null-deref at probe Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 26/47] arm64: mm: avoid calling apply_to_page_range on empty range Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 27/47] x86/mm: Fix types used in pgprot cacheability flags translations Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 20/47] arm64: kernel: fix architected PMU registers unconditional access Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 08/47] ACPI / PCI / hotplug: unlock in error path in acpiphp_enable_slot() Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 29/47] SCSI: fix crashes in sd and sr runtime PM Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 25/47] arm64: errata: Add -mpc-relative-literal-loads to build flags Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:00 +0100
  [PATCH 3.19.y-ckt 07/47] ACPI: Revert "ACPI / video: Add Dell Inspiron 5737 to the blacklist" Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:10 +0100
  [PATCH 3.19.y-ckt 03/47] KVM: PPC: Fix emulation of H_SET_DABR/X on POWER8 Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:10 +0100
  [PATCH 3.19.y-ckt 06/47] powerpc: Simplify module TOC handling Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:10 +0100
  [PATCH 3.19.y-ckt 04/47] KVM: PPC: Fix ONE_REG AltiVec support Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:10 +0100
  [PATCH 3.19.y-ckt 02/47] iio: adis_buffer: Fix out-of-bounds memory access Kamal Mostafa <kamal@canonical.com> - 2016-02-10 00:10 +0100

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