Commit 7ee96216 authored Jan 28, 2016 by Takashi Iwai

ALSA: dummy: Disable switching timer backend via sysfs

ALSA dummy driver can switch the timer backend between system timer
and hrtimer via its hrtimer module option.  This can be also switched
dynamically via sysfs, but it may lead to a memory corruption when
switching is done while a PCM stream is running; the stream instance
for the newly switched timer method tries to access the memory that
was allocated by another timer method although the sizes differ.

As the simplest fix, this patch just disables the switch via sysfs by
dropping the writable bit.

BugLink: http://lkml.kernel.org/r/CACT4Y+ZGEeEBntHW5WHn2GoeE0G_kRrCmUh6=dWyy-wfzvuJLg@mail.gmail.com


Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent ac1efcfb

sound/drivers/dummy.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -87,7 +87,7 @@ MODULE_PARM_DESC(pcm_substreams, "PCM substreams # (1-128) for dummy driver.");
	module_param(fake_buffer, bool, 0444);		module_param(fake_buffer, bool, 0444);
	MODULE_PARM_DESC(fake_buffer, "Fake buffer allocations.");		MODULE_PARM_DESC(fake_buffer, "Fake buffer allocations.");
	#ifdef CONFIG_HIGH_RES_TIMERS		#ifdef CONFIG_HIGH_RES_TIMERS
	module_param(hrtimer, bool, 0644);		module_param(hrtimer, bool, 0444);
	MODULE_PARM_DESC(hrtimer, "Use hrtimer as the timer source.");		MODULE_PARM_DESC(hrtimer, "Use hrtimer as the timer source.");
	#endif		#endif

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