syzkaller triggered kernel warnings through PCM OSS emulation at closing a stream: WARNING: CPU: 0 PID: 3502 at sound/core/pcm_lib.c:1635 snd_pcm_hw_param_first+0x289/0x690 sound/core/pcm_lib.c:1635 Call Trace: .... snd_pcm_hw_param_near.constprop.27+0x78d/0x9a0 sound/core/oss/pcm_oss.c:457 snd_pcm_oss_change_params+0x17d3/0x3720 sound/core/oss/pcm_oss.c:969 snd_pcm_oss_make_ready+0xaa/0x130 sound/core/oss/pcm_oss.c:1128 snd_pcm_oss_sync+0x257/0x830 sound/core/oss/pcm_oss.c:1638 snd_pcm_oss_release+0x20b/0x280 sound/core/oss/pcm_oss.c:2431 __fput+0x327/0x7e0 fs/file_table.c:210 ....

This happens while it tries to open and set up the aloop device concurrently. The warning above (invoked from snd_BUG_ON() macro) is to detect the unexpected logical error where snd_pcm_hw_refine() call shouldn't fail. The theory is true for the case where the hw_params config rules are static. But for an aloop device, the hw_params rule condition does vary dynamically depending on the connected target; when another device is opened and changes the parameters, the device connected in another side is also affected, and it caused the error from snd_pcm_hw_refine().

That is, the simplest "solution" for this is to remove the incorrect assumption of static rules, and treat such an error as a normal error path. As there are a couple of other places using snd_BUG_ON() incorrectly, this patch removes these spurious snd_BUG_ON() calls.

Reported-by: syzbot+6f11c7e2a1b91d466432@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/core/oss/pcm_oss.c | 1 - sound/core/pcm_lib.c | 4 ++-- 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c index e49f448ee04f..ceaa51f76591 100644 --- a/sound/core/oss/pcm_oss.c +++ b/sound/core/oss/pcm_oss.c @@ -455,7 +455,6 @@ static int snd_pcm_hw_param_near(struct snd_pcm_substream *pcm, v = snd_pcm_hw_param_last(pcm, params, var, dir); else v = snd_pcm_hw_param_first(pcm, params, var, dir); - snd_BUG_ON(v < 0); return v; }

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index 10e7ef7a8804..db7894bb028c 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1632,7 +1632,7 @@ int snd_pcm_hw_param_first(struct snd_pcm_substream *pcm, return changed; if (params->rmask) { int err = snd_pcm_hw_refine(pcm, params); - if (snd_BUG_ON(err < 0)) + if (err < 0) return err; } return snd_pcm_hw_param_value(params, var, dir); @@ -1678,7 +1678,7 @@ int snd_pcm_hw_param_last(struct snd_pcm_substream *pcm, return changed; if (params->rmask) { int err = snd_pcm_hw_refine(pcm, params); - if (snd_BUG_ON(err < 0)) + if (err < 0) return err; } return snd_pcm_hw_param_value(params, var, dir);