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authorTakashi Iwai <tiwai@suse.de>2018-04-07 11:48:58 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-04-24 09:29:27 +0200
commitc9c4ad4d4c12f178671ebb2b2f7e84aab32d0972 (patch)
tree0759ef059da5252d2c97d7e5ef191ad9bde9077c /sound/core
parent45ee7eb686073d883a16ceade8da36cb94f34c80 (diff)
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ALSA: pcm: Fix endless loop for XRUN recovery in OSS emulation
commit e15dc99dbb9cf99f6432e8e3c0b3a8f7a3403a86 upstream. The commit 02a5d6925cd3 ("ALSA: pcm: Avoid potential races between OSS ioctls and read/write") split the PCM preparation code to a locked version, and it added a sanity check of runtime->oss.prepare flag along with the change. This leaded to an endless loop when the stream gets XRUN: namely, snd_pcm_oss_write3() and co call snd_pcm_oss_prepare() without setting runtime->oss.prepare flag and the loop continues until the PCM state reaches to another one. As the function is supposed to execute the preparation unconditionally, drop the invalid state check there. The bug was triggered by syzkaller. Fixes: 02a5d6925cd3 ("ALSA: pcm: Avoid potential races between OSS ioctls and read/write") Reported-by: syzbot+150189c103427d31a053@syzkaller.appspotmail.com Reported-by: syzbot+7e3f31a52646f939c052@syzkaller.appspotmail.com Reported-by: syzbot+4f2016cf5185da7759dc@syzkaller.appspotmail.com Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'sound/core')
-rw-r--r--sound/core/oss/pcm_oss.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
index 0c03f97a6ea0..e3c5fee7f838 100644
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -1139,13 +1139,14 @@ static int snd_pcm_oss_get_active_substream(struct snd_pcm_oss_file *pcm_oss_fil
}
/* call with params_lock held */
+/* NOTE: this always call PREPARE unconditionally no matter whether
+ * runtime->oss.prepare is set or not
+ */
static int snd_pcm_oss_prepare(struct snd_pcm_substream *substream)
{
int err;
struct snd_pcm_runtime *runtime = substream->runtime;
- if (!runtime->oss.prepare)
- return 0;
err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_PREPARE, NULL);
if (err < 0) {
pcm_dbg(substream->pcm,