From 71321eb3f2d0df4e6c327e0b936eec4458a12054 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 28 Feb 2017 14:49:07 +0100 Subject: [PATCH] ALSA: timer: Reject user params with too small ticks When a user sets a too small ticks with a fine-grained timer like hrtimer, the kernel tries to fire up the timer irq too frequently. This may lead to the condensed locks, eventually the kernel spinlock lockup with warnings. For avoiding such a situation, we define a lower limit of the resolution, namely 1ms. When the user passes a too small tick value that results in less than that, the kernel returns -EINVAL now. Reported-by: Dmitry Vyukov Cc: Signed-off-by: Takashi Iwai --- sound/core/timer.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/sound/core/timer.c b/sound/core/timer.c index fc144f4..ad15314 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -1702,9 +1702,21 @@ static int snd_timer_user_params(struct file *file, return -EBADFD; if (copy_from_user(¶ms, _params, sizeof(params))) return -EFAULT; - if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE) && params.ticks < 1) { - err = -EINVAL; - goto _end; + if (!(t->hw.flags & SNDRV_TIMER_HW_SLAVE)) { + u64 resolution; + + if (params.ticks < 1) { + err = -EINVAL; + goto _end; + } + + /* Don't allow resolution less than 1ms */ + resolution = snd_timer_resolution(tu->timeri); + resolution *= params.ticks; + if (resolution < 1000000) { + err = -EINVAL; + goto _end; + } } if (params.queue_size > 0 && (params.queue_size < 32 || params.queue_size > 1024)) { -- 2.7.4