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Groups > linux.kernel > #1329770
| From | Ben Hutchings <ben@decadent.org.uk> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 3.2 57/87] ALSA: timer: Harden slave timer list handling |
| Date | 2016-02-09 01:20 +0100 |
| Message-ID | <r04cb-4m5-35@gated-at.bofh.it> (permalink) |
| References | <r03SN-3V2-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
3.2.77-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Takashi Iwai <tiwai@suse.de>
commit b5a663aa426f4884c71cd8580adae73f33570f0d upstream.
A slave timer instance might be still accessible in a racy way while
operating the master instance as it lacks of locking. Since the
master operation is mostly protected with timer->lock, we should cope
with it while changing the slave instance, too. Also, some linked
lists (active_list and ack_list) of slave instances aren't unlinked
immediately at stopping or closing, and this may lead to unexpected
accesses.
This patch tries to address these issues. It adds spin lock of
timer->lock (either from master or slave, which is equivalent) in a
few places. For avoiding a deadlock, we ensure that the global
slave_active_lock is always locked at first before each timer lock.
Also, ack and active_list of slave instances are properly unlinked at
snd_timer_stop() and snd_timer_close().
Last but not least, remove the superfluous call of _snd_timer_stop()
at removing slave links. This is a noop, and calling it may confuse
readers wrt locking. Further cleanup will follow in a later patch.
Actually we've got reports of use-after-free by syzkaller fuzzer, and
this hopefully fixes these issues.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
sound/core/timer.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -214,11 +214,13 @@ static void snd_timer_check_master(struc
slave->slave_id == master->slave_id) {
list_move_tail(&slave->open_list, &master->slave_list_head);
spin_lock_irq(&slave_active_lock);
+ spin_lock(&master->timer->lock);
slave->master = master;
slave->timer = master->timer;
if (slave->flags & SNDRV_TIMER_IFLG_RUNNING)
list_add_tail(&slave->active_list,
&master->slave_active_head);
+ spin_unlock(&master->timer->lock);
spin_unlock_irq(&slave_active_lock);
}
}
@@ -344,15 +346,18 @@ int snd_timer_close(struct snd_timer_ins
timer->hw.close)
timer->hw.close(timer);
/* remove slave links */
+ spin_lock_irq(&slave_active_lock);
+ spin_lock(&timer->lock);
list_for_each_entry_safe(slave, tmp, &timeri->slave_list_head,
open_list) {
- spin_lock_irq(&slave_active_lock);
- _snd_timer_stop(slave, 1, SNDRV_TIMER_EVENT_RESOLUTION);
list_move_tail(&slave->open_list, &snd_timer_slave_list);
slave->master = NULL;
slave->timer = NULL;
- spin_unlock_irq(&slave_active_lock);
+ list_del_init(&slave->ack_list);
+ list_del_init(&slave->active_list);
}
+ spin_unlock(&timer->lock);
+ spin_unlock_irq(&slave_active_lock);
mutex_unlock(®ister_mutex);
}
out:
@@ -439,9 +444,12 @@ static int snd_timer_start_slave(struct
spin_lock_irqsave(&slave_active_lock, flags);
timeri->flags |= SNDRV_TIMER_IFLG_RUNNING;
- if (timeri->master)
+ if (timeri->master && timeri->timer) {
+ spin_lock(&timeri->timer->lock);
list_add_tail(&timeri->active_list,
&timeri->master->slave_active_head);
+ spin_unlock(&timeri->timer->lock);
+ }
spin_unlock_irqrestore(&slave_active_lock, flags);
return 1; /* delayed start */
}
@@ -487,6 +495,8 @@ static int _snd_timer_stop(struct snd_ti
if (!keep_flag) {
spin_lock_irqsave(&slave_active_lock, flags);
timeri->flags &= ~SNDRV_TIMER_IFLG_RUNNING;
+ list_del_init(&timeri->ack_list);
+ list_del_init(&timeri->active_list);
spin_unlock_irqrestore(&slave_active_lock, flags);
}
goto __end;
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[PATCH 3.2 00/87] 3.2.77-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 79/87] crypto: af_alg - Forbid bind(2) when nokey child sockets are present Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 17/87] asix: silence log message from oversize packet Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 73/87] crypto: algif_hash - Require setkey before accept(2) Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 18/87] futex: Drop refcount if requeue_pi() acquired the rtmutex Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 60/87] crypto: af_alg - Fix socket double-free when accept fails Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 72/87] crypto: hash - Add crypto_ahash_has_setkey Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 70/87] crypto: af_alg - Add nokey compatibility path Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 57/87] ALSA: timer: Harden slave timer list handling Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 61/87] ALSA: hrtimer: Fix stall by hrtimer_cancel() Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 82/87] crypto: algif_skcipher - Load TX SG list after waiting Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 11/87] rtlwifi: fix memory leak for USB device Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 64/87] ALSA: control: Avoid kernel warnings from tlv ioctl with numid 0 Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 01/87] [media] gspca: ov534/topro: prevent a division by 0 Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:20 +0100
[PATCH 3.2 08/87] mtd: nand: fix ONFI parameter page layout Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 80/87] crypto: algif_hash - Fix race condition in hash_check_key Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 04/87] SCSI: initio: remove duplicate module device table Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 87/87] [media] usbvision: fix crash on detecting device with invalid configuration Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 15/87] powerpc: Make value-returning atomics fully ordered Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 10/87] xhci: refuse loading if nousb is used Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 05/87] KVM: x86: expose MSR_TSC_AUX to userspace Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 86/87] [media] usbvision fix overflow of interfaces array Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 85/87] [media] usbvision: fix leak of usb_dev on failure paths in usbvision_probe() Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 07/87] ath9k_htc: check for underflow in ath9k_htc_rx_msg() Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 13/87] wlcore/wl12xx: spi: fix oops on firmware load Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 14/87] EDAC: Robustify workqueues destruction Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 19/87] ALSA: fm801: propagate TUNER_ONLY bit when autodetected Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 84/87] [media] usbvision-video: fix memory leak of alt_max_pkt_size Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 12/87] wlcore: SPI - fix spi transfer_list Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 16/87] powerpc: Make {cmp}xchg* and their atomic_ versions fully ordered Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 78/87] crypto: algif_skcipher - Remove custom release parent function Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
[PATCH 3.2 03/87] [media] rc: allow rc modules to be loaded if rc-main is not a module Ben Hutchings <ben@decadent.org.uk> - 2016-02-09 01:30 +0100
Re: [PATCH 3.2 00/87] 3.2.77-rc1 review Guenter Roeck <linux@roeck-us.net> - 2016-02-09 05:00 +0100
Re: [PATCH 3.2 00/87] 3.2.77-rc1 review Ben Hutchings <ben@decadent.org.uk> - 2016-02-10 02:10 +0100
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