This is a note to let you know that I've just added the patch titled
ALSA: pcm: Remove incorrect snd_BUG_ON() usages
to the 4.4-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-remove-incorrect-snd_bug_on-usages.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From fe08f34d066f4404934a509b6806db1a4f700c86 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Mon, 1 Jan 2018 09:50:50 +0100
Subject: ALSA: pcm: Remove incorrect snd_BUG_ON() usages
From: Takashi Iwai <tiwai@xxxxxxx>
commit fe08f34d066f4404934a509b6806db1a4f700c86 upstream.
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/oss/pcm_oss.c | 1 -
sound/core/pcm_lib.c | 4 ++--
2 files changed, 2 insertions(+), 3 deletions(-)
--- a/sound/core/oss/pcm_oss.c
+++ b/sound/core/oss/pcm_oss.c
@@ -465,7 +465,6 @@ static int snd_pcm_hw_param_near(struct
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;
}
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1664,7 +1664,7 @@ int snd_pcm_hw_param_first(struct snd_pc
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);
@@ -1711,7 +1711,7 @@ int snd_pcm_hw_param_last(struct snd_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);
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-4.4/alsa-pcm-remove-incorrect-snd_bug_on-usages.patch
queue-4.4/alsa-aloop-fix-inconsistent-format-due-to-incomplete-rule.patch
queue-4.4/alsa-pcm-add-missing-error-checks-in-oss-emulation-plugin-builder.patch
queue-4.4/alsa-pcm-abort-properly-at-pending-signal-in-oss-read-write-loops.patch
queue-4.4/alsa-pcm-allow-aborting-mutex-lock-at-oss-read-write-loops.patch
queue-4.4/alsa-aloop-fix-racy-hw-constraints-adjustment.patch
queue-4.4/alsa-aloop-release-cable-upon-open-error-path.patch