This is a note to let you know that I've just added the patch titled
ALSA: pcm: Fix potential deadlock in OSS emulation
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-pcm-fix-potential-deadlock-in-oss-emulation.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b248371628aad599a48540962f6b85a21a8a0c3f Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Sun, 31 Jan 2016 10:32:37 +0100
Subject: ALSA: pcm: Fix potential deadlock in OSS emulation
From: Takashi Iwai <tiwai@xxxxxxx>
commit b248371628aad599a48540962f6b85a21a8a0c3f upstream.
There are potential deadlocks in PCM OSS emulation code while
accessing read/write and mmap concurrently. This comes from the
infamous mmap_sem usage in copy_from/to_user(). Namely,
snd_pcm_oss_write() ->
&runtime->oss.params_lock ->
copy_to_user() ->
&mm->mmap_sem
mmap() ->
&mm->mmap_sem ->
snd_pcm_oss_mmap() ->
&runtime->oss.params_lock
Since we can't avoid taking params_lock from mmap code path, use
trylock variant and aborts with -EAGAIN as a workaround of this AB/BA
deadlock.
BugLink: http://lkml.kernel.org/r/CACT4Y+bVrBKDG0G2_AcUgUQa+X91VKTeS4v+wN7BSHwHtqn3kQ@xxxxxxxxxxxxxx
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/oss/pcm_oss.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -834,7 +834,8 @@ static int choose_rate(struct snd_pcm_su
return snd_pcm_hw_param_near(substream, params, SNDRV_PCM_HW_PARAM_RATE, best_rate, NULL);
}
-static int snd_pcm_oss_change_params(struct snd_pcm_substream *substream)
+static int snd_pcm_oss_change_params(struct snd_pcm_substream *substream,
+ bool trylock)
{
struct snd_pcm_runtime *runtime = substream->runtime;
struct snd_pcm_hw_params *params, *sparams;
@@ -848,7 +849,10 @@ static int snd_pcm_oss_change_params(str
struct snd_mask sformat_mask;
struct snd_mask mask;
- if (mutex_lock_interruptible(&runtime->oss.params_lock))
+ if (trylock) {
+ if (!(mutex_trylock(&runtime->oss.params_lock)))
+ return -EAGAIN;
+ } else if (mutex_lock_interruptible(&runtime->oss.params_lock))
return -EINTR;
sw_params = kmalloc(sizeof(*sw_params), GFP_KERNEL);
params = kmalloc(sizeof(*params), GFP_KERNEL);
@@ -1091,7 +1095,7 @@ static int snd_pcm_oss_get_active_substr
if (asubstream == NULL)
asubstream = substream;
if (substream->runtime->oss.params) {
- err = snd_pcm_oss_change_params(substream);
+ err = snd_pcm_oss_change_params(substream, false);
if (err < 0)
return err;
}
@@ -1130,7 +1134,7 @@ static int snd_pcm_oss_make_ready(struct
return 0;
runtime = substream->runtime;
if (runtime->oss.params) {
- err = snd_pcm_oss_change_params(substream);
+ err = snd_pcm_oss_change_params(substream, false);
if (err < 0)
return err;
}
@@ -2168,7 +2172,7 @@ static int snd_pcm_oss_get_space(struct
runtime = substream->runtime;
if (runtime->oss.params &&
- (err = snd_pcm_oss_change_params(substream)) < 0)
+ (err = snd_pcm_oss_change_params(substream, false)) < 0)
return err;
info.fragsize = runtime->oss.period_bytes;
@@ -2804,7 +2808,12 @@ static int snd_pcm_oss_mmap(struct file
return -EIO;
if (runtime->oss.params) {
- if ((err = snd_pcm_oss_change_params(substream)) < 0)
+ /* use mutex_trylock() for params_lock for avoiding a deadlock
+ * between mmap_sem and params_lock taken by
+ * copy_from/to_user() in snd_pcm_oss_write/read()
+ */
+ err = snd_pcm_oss_change_params(substream, true);
+ if (err < 0)
return err;
}
#ifdef CONFIG_SND_PCM_OSS_PLUGINS
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-3.10/alsa-seq-fix-race-at-closing-in-virmidi-driver.patch
queue-3.10/alsa-rawmidi-remove-kernel-warning-for-null-user-space-buffer-check.patch
queue-3.10/alsa-seq-fix-lockdep-warnings-due-to-double-mutex-locks.patch
queue-3.10/alsa-usb-audio-fix-teac-ud-501-ud-503-nt-503-usb-delay.patch
queue-3.10/alsa-timer-fix-wrong-instance-passed-to-slave-callbacks.patch
queue-3.10/alsa-compress-disable-get_codec_caps-ioctl-for-some-architectures.patch
queue-3.10/alsa-hda-fix-speaker-output-from-vaio-aio-machines.patch
queue-3.10/alsa-dummy-implement-timer-backend-switching-more-safely.patch
queue-3.10/alsa-dummy-disable-switching-timer-backend-via-sysfs.patch
queue-3.10/alsa-seq-fix-incorrect-sanity-check-at-snd_seq_oss_synth_cleanup.patch
queue-3.10/alsa-seq-fix-yet-another-races-among-alsa-timer-accesses.patch
queue-3.10/alsa-usb-audio-avoid-freeing-umidi-object-twice.patch
queue-3.10/alsa-timer-fix-leftover-link-at-closing.patch
queue-3.10/alsa-rawmidi-fix-race-at-copying-updating-the-position.patch
queue-3.10/alsa-pcm-fix-potential-deadlock-in-oss-emulation.patch
queue-3.10/alsa-timer-fix-link-corruption-due-to-double-start-or-stop.patch
--
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