From 5061bb7065d05efbac35a660eb30ed4c3100690b Mon Sep 17 00:00:00 2001
From: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Date: Wed, 27 Nov 2019 05:06:22 -0600
Subject: [PATCH] ALSA: aloop: Avoid pointer dereference before null-check
Git-commit: 5061bb7065d05efbac35a660eb30ed4c3100690b
Patch-mainline: v5.5-rc1
References: jsc#SLE-16518
Static analysis tools (cppcheck and PVS Studio) report an error
in loopback_snd_timer_period_elapsed() regarding dpcm_play pointer
dereference earlier than its null-check. And although this is a result
of a formal check, and the pointer correctness is also protected
by having a corresponding bit set in the "running" mask, re-ordering
of the lines can imake the code even formally correct and eliminate
those static analysis error reports.
Fixes: 26c53379f98d ("ALSA: aloop: Support selection of snd_timer instead of jiffies")
Reported-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>
Link: https://lore.kernel.org/r/20191127110622.26105-1-andrew_gabbasov@mentor.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/drivers/aloop.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 0ebfbe70db00..6bb46423f5ae 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -727,10 +727,6 @@ static void loopback_snd_timer_period_elapsed(struct loopback_cable *cable,
dpcm_play = cable->streams[SNDRV_PCM_STREAM_PLAYBACK];
dpcm_capt = cable->streams[SNDRV_PCM_STREAM_CAPTURE];
- substream_play = (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ?
- dpcm_play->substream : NULL;
- substream_capt = (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) ?
- dpcm_capt->substream : NULL;
if (event == SNDRV_TIMER_EVENT_MSTOP) {
if (!dpcm_play ||
@@ -741,6 +737,10 @@ static void loopback_snd_timer_period_elapsed(struct loopback_cable *cable,
}
}
+ substream_play = (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ?
+ dpcm_play->substream : NULL;
+ substream_capt = (running & (1 << SNDRV_PCM_STREAM_CAPTURE)) ?
+ dpcm_capt->substream : NULL;
valid_runtime = (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ?
dpcm_play->substream->runtime :
dpcm_capt->substream->runtime;
--
2.16.4