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[PATCH 3.2 52/62] ALSA: seq: oss: Don't drain at closing a client

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3.2.79-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 197b958c1e76a575d77038cc98b4bebc2134279f upstream.

The OSS sequencer client tries to drain the pending events at
releasing.  Unfortunately, as spotted by syzkaller fuzzer, this may
lead to an unkillable process state when the event has been queued at
the far future.  Since the process being released can't be signaled
any longer, it remains and waits for the echo-back event in that far
future.

Back to history, the draining feature was implemented at the time we
misinterpreted POSIX definition for blocking file operation.
Actually, such a behavior is superfluous at release, and we should
just release the device as is instead of keeping it up forever.

This patch just removes the draining call that may block the release
for too long time unexpectedly.

BugLink: http://lkml.kernel.org/r/CACT4Y+Y4kD-aBGj37rf-xBw9bH3GMU6P+MYg4W1e-s-paVD2pg@mail.gmail.com
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[bwh: Backported to 3.2: snd_seq_oss_drain_write() has an extra log statement
 to be deleted]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 sound/core/seq/oss/seq_oss.c        |  2 --
 sound/core/seq/oss/seq_oss_device.h |  1 -
 sound/core/seq/oss/seq_oss_init.c   | 16 ----------------
 3 files changed, 19 deletions(-)

--- a/sound/core/seq/oss/seq_oss.c
+++ b/sound/core/seq/oss/seq_oss.c
@@ -150,8 +150,6 @@ odev_release(struct inode *inode, struct
 	if ((dp = file->private_data) == NULL)
 		return 0;
 
-	snd_seq_oss_drain_write(dp);
-
 	mutex_lock(&register_mutex);
 	snd_seq_oss_release(dp);
 	mutex_unlock(&register_mutex);
--- a/sound/core/seq/oss/seq_oss_device.h
+++ b/sound/core/seq/oss/seq_oss_device.h
@@ -131,7 +131,6 @@ int snd_seq_oss_write(struct seq_oss_dev
 unsigned int snd_seq_oss_poll(struct seq_oss_devinfo *dp, struct file *file, poll_table * wait);
 
 void snd_seq_oss_reset(struct seq_oss_devinfo *dp);
-void snd_seq_oss_drain_write(struct seq_oss_devinfo *dp);
 
 /* */
 void snd_seq_oss_process_queue(struct seq_oss_devinfo *dp, abstime_t time);
--- a/sound/core/seq/oss/seq_oss_init.c
+++ b/sound/core/seq/oss/seq_oss_init.c
@@ -447,23 +447,6 @@ snd_seq_oss_release(struct seq_oss_devin
 
 
 /*
- * Wait until the queue is empty (if we don't have nonblock)
- */
-void
-snd_seq_oss_drain_write(struct seq_oss_devinfo *dp)
-{
-	if (! dp->timer->running)
-		return;
-	if (is_write_mode(dp->file_mode) && !is_nonblock_mode(dp->file_mode) &&
-	    dp->writeq) {
-		debug_printk(("syncing..\n"));
-		while (snd_seq_oss_writeq_sync(dp->writeq))
-			;
-	}
-}
-
-
-/*
  * reset sequencer devices
  */
 void

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[PATCH 3.2 00/62] 3.2.79-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 27/62] USB: option: add support for SIM7100E Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 13/62] xen/pciback: Check PF instead of VF for  PCI_COMMAND_MEMORY Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 12/62] libata: fix HDIO_GET_32BIT ioctl Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 52/62] ALSA: seq: oss: Don't drain at closing a client Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 41/62] ipr: Fix out-of-bounds null overwrite Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 20/62] af_unix: Don't set err in unix_stream_read_generic  unless there was an error Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 21/62] af_unix: Guard against other == sk in  unix_dgram_sendmsg Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 35/62] sunrpc/cache: fix off-by-one in qword_get() Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 42/62] ipr: Fix regression when loading firmware Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 15/62] xen/pcifront: Fix mysterious crashes when NUMA  locality information was extracted. Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 50/62] ASoC: wm8994: Fix enum ctl accesses in a wrong type Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 49/62] ASoC: wm8958: Fix enum ctl accesses in a wrong type Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:20 +0200
  [PATCH 3.2 57/62] ubi: Fix out of bounds write in volume update code Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 03/62] iommu/vt-d: Fix 64-bit accesses to 32-bit  DMAR_GSTS_REG Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 45/62] ALSA: timer: Fix broken compat timer user  status ioctl Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 05/62] cfg80211/wext: fix message ordering Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 14/62] xen/pciback: Save the number of MSI-X entries  to be copied later. Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 18/62] tracing: Fix freak link error caused by branch  tracer Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 16/62] ALSA: seq: Fix leak of pool buffer at  concurrent writes Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 62/62] HID: usbhid: fix recursive deadlock Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 08/62] drm/i915: fix error path in intel_setup_gmbus() Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 19/62] ALSA: seq: Fix double port list deletion Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 58/62] Revert "drm/radeon: call hpd_irq_event on resume" Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 10/62] s390/dasd: prevent incorrect length error under  z/VM after PAV changes Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 07/62] nfs: fix nfs_size_to_loff_t Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 04/62] wext: fix message delay/ordering Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 06/62] mac80211: fix use of uninitialised values in RX  aggregation Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 46/62] ALSA: hdspm: Fix wrong boolean ctl value accesses Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 01/62] Revert "crypto: algif_skcipher - Do not  dereference ctx without socket lock" Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  [PATCH 3.2 17/62] tracepoints: Do not trace when cpu is offline Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200
  Re: [PATCH 3.2 00/62] 3.2.79-rc1 review Guenter Roeck <linux@roeck-us.net> - 2016-03-29 22:30 +0200
    Re: [PATCH 3.2 00/62] 3.2.79-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 23:10 +0200
  [PATCH 3.2 02/62] crypto: {blk,giv}cipher: Set has_setkey Ben Hutchings <ben@decadent.org.uk> - 2016-03-29 22:30 +0200

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