From 3ed5d283254aab50d90525d8ea4dd713aac08d1d Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Sat, 30 Jan 2016 23:30:25 +0100 Subject: [PATCH] ALSA: seq: Fix yet another races among ALSA timer accesses commit 2cdc7b636d55cbcf42e1e6c8accd85e62d3e9ae8 upstream. ALSA sequencer may open/close and control ALSA timer instance dynamically either via sequencer events or direct ioctls. These are done mostly asynchronously, and it may call still some timer action like snd_timer_start() while another is calling snd_timer_close(). Since the instance gets removed by snd_timer_close(), it may lead to a use-after-free. This patch tries to address such a race by protecting each snd_timer_*() call via the existing spinlock and also by avoiding the access to timer during close call. BugLink: http://lkml.kernel.org/r/CACT4Y+Z6RzW5MBr-HUdV-8zwg71WQfKTdPpYGvOeS7v4cyurNQ@mail.gmail.com Reported-by: Dmitry Vyukov Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman --- sound/core/seq/seq_timer.c | 87 +++++++++++++++++++++++++++++--------- 1 file changed, 67 insertions(+), 20 deletions(-) diff --git a/sound/core/seq/seq_timer.c b/sound/core/seq/seq_timer.c index 82b220c769c1..293104926098 100644 --- a/sound/core/seq/seq_timer.c +++ b/sound/core/seq/seq_timer.c @@ -90,6 +90,9 @@ void snd_seq_timer_delete(struct snd_seq_timer **tmr) void snd_seq_timer_defaults(struct snd_seq_timer * tmr) { + unsigned long flags; + + spin_lock_irqsave(&tmr->lock, flags); /* setup defaults */ tmr->ppq = 96; /* 96 PPQ */ tmr->tempo = 500000; /* 120 BPM */ @@ -105,21 +108,25 @@ void snd_seq_timer_defaults(struct snd_seq_timer * tmr) tmr->preferred_resolution = seq_default_timer_resolution; tmr->skew = tmr->skew_base = SKEW_BASE; + spin_unlock_irqrestore(&tmr->lock, flags); } -void snd_seq_timer_reset(struct snd_seq_timer * tmr) +static void seq_timer_reset(struct snd_seq_timer *tmr) { - unsigned long flags; - - spin_lock_irqsave(&tmr->lock, flags); - /* reset time & songposition */ tmr->cur_time.tv_sec = 0; tmr->cur_time.tv_nsec = 0; tmr->tick.cur_tick = 0; tmr->tick.fraction = 0; +} + +void snd_seq_timer_reset(struct snd_seq_timer *tmr) +{ + unsigned long flags; + spin_lock_irqsave(&tmr->lock, flags); + seq_timer_reset(tmr); spin_unlock_irqrestore(&tmr->lock, flags); } @@ -138,8 +145,11 @@ static void snd_seq_timer_interrupt(struct snd_timer_instance *timeri, tmr = q->timer; if (tmr == NULL) return; - if (!tmr->running) + spin_lock_irqsave(&tmr->lock, flags); + if (!tmr->running) { + spin_unlock_irqrestore(&tmr->lock, flags); return; + } resolution *= ticks; if (tmr->skew != tmr->skew_base) { @@ -148,8 +158,6 @@ static void snd_seq_timer_interrupt(struct snd_timer_instance *timeri, (((resolution & 0xffff) * tmr->skew) >> 16); } - spin_lock_irqsave(&tmr->lock, flags); - /* update timer */ snd_seq_inc_time_nsec(&tmr->cur_time, resolution); @@ -296,26 +304,30 @@ int snd_seq_timer_open(struct snd_seq_queue *q) t->callback = snd_seq_timer_interrupt; t->callback_data = q; t->flags |= SNDRV_TIMER_IFLG_AUTO; + spin_lock_irq(&tmr->lock); tmr->timeri = t; + spin_unlock_irq(&tmr->lock); return 0; } int snd_seq_timer_close(struct snd_seq_queue *q) { struct snd_seq_timer *tmr; + struct snd_timer_instance *t; tmr = q->timer; if (snd_BUG_ON(!tmr)) return -EINVAL; - if (tmr->timeri) { - snd_timer_stop(tmr->timeri); - snd_timer_close(tmr->timeri); - tmr->timeri = NULL; - } + spin_lock_irq(&tmr->lock); + t = tmr->timeri; + tmr->timeri = NULL; + spin_unlock_irq(&tmr->lock); + if (t) + snd_timer_close(t); return 0; } -int snd_seq_timer_stop(struct snd_seq_timer * tmr) +static int seq_timer_stop(struct snd_seq_timer *tmr) { if (! tmr->timeri) return -EINVAL; @@ -326,6 +338,17 @@ int snd_seq_timer_stop(struct snd_seq_timer * tmr) return 0; } +int snd_seq_timer_stop(struct snd_seq_timer *tmr) +{ + unsigned long flags; + int err; + + spin_lock_irqsave(&tmr->lock, flags); + err = seq_timer_stop(tmr); + spin_unlock_irqrestore(&tmr->lock, flags); + return err; +} + static int initialize_timer(struct snd_seq_timer *tmr) { struct snd_timer *t; @@ -358,13 +381,13 @@ static int initialize_timer(struct snd_seq_timer *tmr) return 0; } -int snd_seq_timer_start(struct snd_seq_timer * tmr) +static int seq_timer_start(struct snd_seq_timer *tmr) { if (! tmr->timeri) return -EINVAL; if (tmr->running) - snd_seq_timer_stop(tmr); - snd_seq_timer_reset(tmr); + seq_timer_stop(tmr); + seq_timer_reset(tmr); if (initialize_timer(tmr) < 0) return -EINVAL; snd_timer_start(tmr->timeri, tmr->ticks); @@ -373,14 +396,25 @@ int snd_seq_timer_start(struct snd_seq_timer * tmr) return 0; } -int snd_seq_timer_continue(struct snd_seq_timer * tmr) +int snd_seq_timer_start(struct snd_seq_timer *tmr) +{ + unsigned long flags; + int err; + + spin_lock_irqsave(&tmr->lock, flags); + err = seq_timer_start(tmr); + spin_unlock_irqrestore(&tmr->lock, flags); + return err; +} + +static int seq_timer_continue(struct snd_seq_timer *tmr) { if (! tmr->timeri) return -EINVAL; if (tmr->running) return -EBUSY; if (! tmr->initialized) { - snd_seq_timer_reset(tmr); + seq_timer_reset(tmr); if (initialize_timer(tmr) < 0) return -EINVAL; } @@ -390,11 +424,24 @@ int snd_seq_timer_continue(struct snd_seq_timer * tmr) return 0; } +int snd_seq_timer_continue(struct snd_seq_timer *tmr) +{ + unsigned long flags; + int err; + + spin_lock_irqsave(&tmr->lock, flags); + err = seq_timer_continue(tmr); + spin_unlock_irqrestore(&tmr->lock, flags); + return err; +} + /* return current 'real' time. use timeofday() to get better granularity. */ snd_seq_real_time_t snd_seq_timer_get_cur_time(struct snd_seq_timer *tmr) { snd_seq_real_time_t cur_time; + unsigned long flags; + spin_lock_irqsave(&tmr->lock, flags); cur_time = tmr->cur_time; if (tmr->running) { struct timeval tm; @@ -410,7 +457,7 @@ snd_seq_real_time_t snd_seq_timer_get_cur_time(struct snd_seq_timer *tmr) } snd_seq_sanity_real_time(&cur_time); } - + spin_unlock_irqrestore(&tmr->lock, flags); return cur_time; } -- 2.34.1