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Groups > linux.kernel > #1537534

[PATCH 4.4 05/13] ALSA: pcm : Call kill_fasync() in stream lock

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

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

From: Takashi Iwai <tiwai@suse.de>

commit 3aa02cb664c5fb1042958c8d1aa8c35055a2ebc4 upstream.

Currently kill_fasync() is called outside the stream lock in
snd_pcm_period_elapsed().  This is potentially racy, since the stream
may get released even during the irq handler is running.  Although
snd_pcm_release_substream() calls snd_pcm_drop(), this doesn't
guarantee that the irq handler finishes, thus the kill_fasync() call
outside the stream spin lock may be invoked after the substream is
detached, as recently reported by KASAN.

As a quick workaround, move kill_fasync() call inside the stream
lock.  The fasync is rarely used interface, so this shouldn't have a
big impact from the performance POV.

Ideally, we should implement some sync mechanism for the proper finish
of stream and irq handler.  But this oneliner should suffice for most
cases, so far.

Reported-by: Baozeng Ding <sploving1@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 sound/core/pcm_lib.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1886,8 +1886,8 @@ void snd_pcm_period_elapsed(struct snd_p
 		snd_timer_interrupt(substream->timer, 1);
 #endif
  _end:
-	snd_pcm_stream_unlock_irqrestore(substream, flags);
 	kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
+	snd_pcm_stream_unlock_irqrestore(substream, flags);
 }
 
 EXPORT_SYMBOL(snd_pcm_period_elapsed);

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[PATCH 4.4 00/13] 4.4.37-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 02/13] zram: fix unbalanced idr management at hot removal Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 05/13] ALSA: pcm : Call kill_fasync() in stream lock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 07/13] PCI: Export pcie_find_root_port Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 11/13] arm64: cpufeature: Schedule enable() calls instead of calling them via IPI Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 10/13] pwm: Fix device reference leak Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 06/13] rcu: Fix soft lockup for rcu_nocb_kthread Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 09/13] mwifiex: printk() overflow with 32-byte SSIDs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 04/13] x86/traps: Ignore high word of regs->cs in early_fixup_exception() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:10 +0100
  [PATCH 4.4 13/13] arm64: suspend: Reconfigure PSTATE after resume from idle Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.4 01/13] ARC: Dont use "+l" inline asm constraint Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  [PATCH 4.4 03/13] kasan: update kasan_global for gcc 7 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-07 08:20 +0100
  Re: [PATCH 4.4 00/13] 4.4.37-stable review Guenter Roeck <linux@roeck-us.net> - 2016-12-07 17:10 +0100
  Re: [PATCH 4.4 00/13] 4.4.37-stable review Shuah Khan <shuah.kh@samsung.com> - 2016-12-07 19:20 +0100
  Re: [PATCH 4.4 00/13] 4.4.37-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-12-08 17:30 +0100

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