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authorTakashi Iwai <tiwai@suse.de>2017-02-28 14:49:07 +0100
committerTakashi Iwai <tiwai@suse.de>2017-02-28 15:06:01 +0100
commit71321eb3f2d0df4e6c327e0b936eec4458a12054 (patch)
tree71fcacadc0b01afc9f386840d8089322631c2332
parent126cfa2f5e15ae2ca7f70be71b07e6cd8d2b44d1 (diff)
downloadlinux-71321eb3f2d0df4e6c327e0b936eec4458a12054.tar.bz2
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 <dvyukov@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/core/timer.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/sound/core/timer.c b/sound/core/timer.c
index fc144f43faa6..ad153149b231 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(&params, _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)) {