linux-kernel - [PATCH 4.1 040/123] ALSA: pcm: Fix lockdep warning with nonatomic PCM ops

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat,  8 Aug 2015 15:08:38 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	Jeeja Kp <jeeja.kp@...el.com>, Takashi Iwai <tiwai@...e.de>
Subject: [PATCH 4.1 040/123] ALSA: pcm: Fix lockdep warning with nonatomic PCM ops

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@...e.de>

commit 67756e3191c90e7c0b94b8b2fb63de255b6cd337 upstream.

With the nonatomic PCM ops, the system may spew lockdep warnings like:

 =============================================
 [ INFO: possible recursive locking detected ]
 4.2.0-rc1-jeejaval3 #12 Not tainted
 ---------------------------------------------
 aplay/4029 is trying to acquire lock:
  (snd_pcm_link_rwsem){.+.+.+}, at: [<ffffffff816fd473>] snd_pcm_stream_lock+0x43/0x60

 but task is already holding lock:
  (snd_pcm_link_rwsem){.+.+.+}, at: [<ffffffff816fcf29>] snd_pcm_action_nonatomic+0x29/0x80

 other info that might help us debug this:
  Possible unsafe locking scenario:

        CPU0
        ----
   lock(snd_pcm_link_rwsem);
   lock(snd_pcm_link_rwsem);

Although this is false-positive as the rwsem is taken always as
read-only for these code paths, it's certainly annoying to see this at
any occasion.  A simple fix is to use down_read_nested() in
snd_pcm_stream_lock() that can be called inside another lock.

Reported-by: Vinod Koul <vinod.koul@...el.com>
Reported-by: Jeeja Kp <jeeja.kp@...el.com>
Tested-by: Jeeja Kp <jeeja.kp@...el.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 sound/core/pcm_native.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -85,7 +85,7 @@ static DECLARE_RWSEM(snd_pcm_link_rwsem)
 void snd_pcm_stream_lock(struct snd_pcm_substream *substream)
 {
 	if (substream->pcm->nonatomic) {
-		down_read(&snd_pcm_link_rwsem);
+		down_read_nested(&snd_pcm_link_rwsem, SINGLE_DEPTH_NESTING);
 		mutex_lock(&substream->self_group.mutex);
 	} else {
 		read_lock(&snd_pcm_link_rwlock);


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/