On Thu, 28 Jan 2016 07:38:08 +0100, Takashi Iwai wrote:
The easiest fix for this is obviously to disable the switch via sysfs like below. Meanwhile we may copy the ops to the runtime instance so that it won't affect the running stream. This can be done for 4.6, while disabling sysfs for 4.5 and stable.
FWIW, below is the patch with a proper description.
Takashi
-- 8< -- From: Takashi Iwai tiwai@suse.de Subject: [PATCH] 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... Reported-by: Dmitry Vyukov dvyukov@google.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/drivers/dummy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index 75b74850c005..bde33308f0d6 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -87,7 +87,7 @@ MODULE_PARM_DESC(pcm_substreams, "PCM substreams # (1-128) for dummy driver."); module_param(fake_buffer, bool, 0444); MODULE_PARM_DESC(fake_buffer, "Fake buffer allocations."); #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."); #endif