* [PATCH 0/2] ALSA: pcm: stream linking locking fixes @ 2020-06-08 10:06 Michał Mirosław 2020-06-08 10:06 ` [PATCH 1/2] ALSA: pcm: disallow linking stream to itself Michał Mirosław 2020-06-08 10:06 ` [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat Michał Mirosław 0 siblings, 2 replies; 7+ messages in thread From: Michał Mirosław @ 2020-06-08 10:06 UTC (permalink / raw) To: Jaroslav Kysela, Takashi Iwai; +Cc: alsa-devel, linux-kernel Two patches fixing locking issues for SNDRV_PCM_IOCTL_LINK handling: first adds a check preventing linking a stream to itself, second quiets lockdep warning about nested locks. Michał Mirosław (2): ALSA: pcm: disallow linking stream to itself ALSA: pcm: fix snd_pcm_link() lockdep splat sound/core/pcm_native.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) -- 2.20.1 ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH 1/2] ALSA: pcm: disallow linking stream to itself 2020-06-08 10:06 [PATCH 0/2] ALSA: pcm: stream linking locking fixes Michał Mirosław @ 2020-06-08 10:06 ` Michał Mirosław 2020-06-08 12:48 ` Takashi Iwai 2020-06-08 10:06 ` [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat Michał Mirosław 1 sibling, 1 reply; 7+ messages in thread From: Michał Mirosław @ 2020-06-08 10:06 UTC (permalink / raw) To: Jaroslav Kysela, Takashi Iwai; +Cc: alsa-devel, linux-kernel Prevent SNDRV_PCM_IOCTL_LINK linking stream to itself - the code can't handle it. Fixed commit is not where bug was introduced, but changes the context significantly. Cc: stable@vger.kernel.org Fixes: 0888c321de70 ("pcm_native: switch to fdget()/fdput()") Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> --- sound/core/pcm_native.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index aef860256278..3ad399cb6f30 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2166,6 +2166,12 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) } pcm_file = f.file->private_data; substream1 = pcm_file->substream; + + if (substream == substream1) { + res = -EDEADLK; + goto _badf; + } + group = kzalloc(sizeof(*group), GFP_KERNEL); if (!group) { res = -ENOMEM; -- 2.20.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 1/2] ALSA: pcm: disallow linking stream to itself 2020-06-08 10:06 ` [PATCH 1/2] ALSA: pcm: disallow linking stream to itself Michał Mirosław @ 2020-06-08 12:48 ` Takashi Iwai 2020-06-08 16:50 ` [PATCH v2] " Michał Mirosław 0 siblings, 1 reply; 7+ messages in thread From: Takashi Iwai @ 2020-06-08 12:48 UTC (permalink / raw) To: Michał Mirosław; +Cc: linux-kernel, alsa-devel, Takashi Iwai On Mon, 08 Jun 2020 12:06:32 +0200, Michał Mirosław wrote: > > Prevent SNDRV_PCM_IOCTL_LINK linking stream to itself - the code > can't handle it. Fixed commit is not where bug was introduced, but > changes the context significantly. > > Cc: stable@vger.kernel.org > Fixes: 0888c321de70 ("pcm_native: switch to fdget()/fdput()") > Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> Thanks for the fix. Just a minor point: > @@ -2166,6 +2166,12 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) > } > pcm_file = f.file->private_data; > substream1 = pcm_file->substream; > + > + if (substream == substream1) { > + res = -EDEADLK; We've never used this error code, hence it may confuse the user-space side. I'd use a more standard -EINVAL instead; the error is basically an invalid argument, after all. thanks, Takashi ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v2] ALSA: pcm: disallow linking stream to itself 2020-06-08 12:48 ` Takashi Iwai @ 2020-06-08 16:50 ` Michał Mirosław 2020-06-08 17:35 ` Takashi Iwai 0 siblings, 1 reply; 7+ messages in thread From: Michał Mirosław @ 2020-06-08 16:50 UTC (permalink / raw) To: Jaroslav Kysela, Takashi Iwai; +Cc: alsa-devel, linux-kernel Prevent SNDRV_PCM_IOCTL_LINK linking stream to itself - the code can't handle it. Fixed commit is not where bug was introduced, but changes the context significantly. Cc: stable@vger.kernel.org Fixes: 0888c321de70 ("pcm_native: switch to fdget()/fdput()") Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> --- v2: EDEADLK -> EINVAL --- sound/core/pcm_native.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index aef860256278..434e7b604bad 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -2166,6 +2166,12 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) } pcm_file = f.file->private_data; substream1 = pcm_file->substream; + + if (substream == substream1) { + res = -EINVAL; + goto _badf; + } + group = kzalloc(sizeof(*group), GFP_KERNEL); if (!group) { res = -ENOMEM; -- 2.20.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH v2] ALSA: pcm: disallow linking stream to itself 2020-06-08 16:50 ` [PATCH v2] " Michał Mirosław @ 2020-06-08 17:35 ` Takashi Iwai 0 siblings, 0 replies; 7+ messages in thread From: Takashi Iwai @ 2020-06-08 17:35 UTC (permalink / raw) To: Michał Mirosław; +Cc: linux-kernel, alsa-devel, Takashi Iwai On Mon, 08 Jun 2020 18:50:39 +0200, Michał Mirosław wrote: > > Prevent SNDRV_PCM_IOCTL_LINK linking stream to itself - the code > can't handle it. Fixed commit is not where bug was introduced, but > changes the context significantly. > > Cc: stable@vger.kernel.org > Fixes: 0888c321de70 ("pcm_native: switch to fdget()/fdput()") > Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> > --- > v2: EDEADLK -> EINVAL Applied now. Thanks! Takashi ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat 2020-06-08 10:06 [PATCH 0/2] ALSA: pcm: stream linking locking fixes Michał Mirosław 2020-06-08 10:06 ` [PATCH 1/2] ALSA: pcm: disallow linking stream to itself Michał Mirosław @ 2020-06-08 10:06 ` Michał Mirosław 2020-06-08 13:02 ` Takashi Iwai 1 sibling, 1 reply; 7+ messages in thread From: Michał Mirosław @ 2020-06-08 10:06 UTC (permalink / raw) To: Jaroslav Kysela, Takashi Iwai; +Cc: alsa-devel, linux-kernel Add and use snd_pcm_stream_lock_nested() in snd_pcm_link/unlink implementation. The code is fine, but generates a lockdep complaint: ============================================ WARNING: possible recursive locking detected 5.7.1mq+ #381 Tainted: G O -------------------------------------------- pulseaudio/4180 is trying to acquire lock: ffff888402d6f508 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xda8/0xee0 [snd_pcm] but task is already holding lock: ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm] other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&group->lock); lock(&group->lock); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by pulseaudio/4180: #0: ffffffffa1a05190 (snd_pcm_link_rwsem){++++}-{3:3}, at: snd_pcm_common_ioctl+0xca0/0xee0 [snd_pcm] #1: ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm] [...] Cc: stable@vger.kernel.org Fixes: f57f3df03a8e ("ALSA: pcm: More fine-grained PCM link locking") Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> --- sound/core/pcm_native.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 3ad399cb6f30..5b36881f7095 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -138,6 +138,16 @@ void snd_pcm_stream_lock_irq(struct snd_pcm_substream *substream) } EXPORT_SYMBOL_GPL(snd_pcm_stream_lock_irq); +static void snd_pcm_stream_lock_nested(struct snd_pcm_substream *substream) +{ + struct snd_pcm_group *group = &substream->self_group; + + if (substream->pcm->nonatomic) + mutex_lock_nested(&group->mutex, SINGLE_DEPTH_NESTING); + else + spin_lock_nested(&group->lock, SINGLE_DEPTH_NESTING); +} + /** * snd_pcm_stream_unlock_irq - Unlock the PCM stream * @substream: PCM substream @@ -2200,7 +2210,7 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) snd_pcm_stream_unlock_irq(substream); snd_pcm_group_lock_irq(target_group, nonatomic); - snd_pcm_stream_lock(substream1); + snd_pcm_stream_lock_nested(substream1); snd_pcm_group_assign(substream1, target_group); refcount_inc(&target_group->refs); snd_pcm_stream_unlock(substream1); @@ -2216,7 +2226,7 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) static void relink_to_local(struct snd_pcm_substream *substream) { - snd_pcm_stream_lock(substream); + snd_pcm_stream_lock_nested(substream); snd_pcm_group_assign(substream, &substream->self_group); snd_pcm_stream_unlock(substream); } -- 2.20.1 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat 2020-06-08 10:06 ` [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat Michał Mirosław @ 2020-06-08 13:02 ` Takashi Iwai 0 siblings, 0 replies; 7+ messages in thread From: Takashi Iwai @ 2020-06-08 13:02 UTC (permalink / raw) To: Michał Mirosław; +Cc: linux-kernel, alsa-devel, Takashi Iwai On Mon, 08 Jun 2020 12:06:32 +0200, Michał Mirosław wrote: > > Add and use snd_pcm_stream_lock_nested() in snd_pcm_link/unlink > implementation. The code is fine, but generates a lockdep complaint: > > ============================================ > WARNING: possible recursive locking detected > 5.7.1mq+ #381 Tainted: G O > -------------------------------------------- > pulseaudio/4180 is trying to acquire lock: > ffff888402d6f508 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xda8/0xee0 [snd_pcm] > > but task is already holding lock: > ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm] > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&group->lock); > lock(&group->lock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 2 locks held by pulseaudio/4180: > #0: ffffffffa1a05190 (snd_pcm_link_rwsem){++++}-{3:3}, at: snd_pcm_common_ioctl+0xca0/0xee0 [snd_pcm] > #1: ffff8883f7a8cf18 (&group->lock){-...}-{2:2}, at: snd_pcm_common_ioctl+0xe4e/0xee0 [snd_pcm] > [...] > > Cc: stable@vger.kernel.org > Fixes: f57f3df03a8e ("ALSA: pcm: More fine-grained PCM link locking") > Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> Applied now. Thanks. Takashi ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2020-06-08 17:36 UTC | newest] Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-06-08 10:06 [PATCH 0/2] ALSA: pcm: stream linking locking fixes Michał Mirosław 2020-06-08 10:06 ` [PATCH 1/2] ALSA: pcm: disallow linking stream to itself Michał Mirosław 2020-06-08 12:48 ` Takashi Iwai 2020-06-08 16:50 ` [PATCH v2] " Michał Mirosław 2020-06-08 17:35 ` Takashi Iwai 2020-06-08 10:06 ` [PATCH 2/2] ALSA: pcm: fix snd_pcm_link() lockdep splat Michał Mirosław 2020-06-08 13:02 ` Takashi Iwai
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