[PATCH 5.10 111/167] ALSA: sb: Fix potential ABBA deadlock in CSP driver
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2021-07-26 16:25:52
Also in:
lkml
From: Takashi Iwai <redacted>
commit 1c2b9519159b470ef24b2638f4794e86e2952ab7 upstream.
SB16 CSP driver may hit potentially a typical ABBA deadlock in two
code paths:
In snd_sb_csp_stop():
spin_lock_irqsave(&p->chip->mixer_lock, flags);
spin_lock(&p->chip->reg_lock);
In snd_sb_csp_load():
spin_lock_irqsave(&p->chip->reg_lock, flags);
spin_lock(&p->chip->mixer_lock);
Also the similar pattern is seen in snd_sb_csp_start().
Although the practical impact is very small (those states aren't
triggered in the same running state and this happens only on a real
hardware, decades old ISA sound boards -- which must be very difficult
to find nowadays), it's a real scenario and has to be fixed.
This patch addresses those deadlocks by splitting the locks in
snd_sb_csp_start() and snd_sb_csp_stop() for avoiding the nested
locks.
Reported-by: Jia-Ju Bai <redacted>
Cc: <redacted>
Link: https://lore.kernel.org/r/7b0fcdaf-cd4f-4728-2eae-48c151a92e10@gmail.com (local)
Link: https://lore.kernel.org/r/20210716132723.13216-1-tiwai@suse.de (local)
Signed-off-by: Takashi Iwai <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/isa/sb/sb16_csp.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/sound/isa/sb/sb16_csp.c
+++ b/sound/isa/sb/sb16_csp.c@@ -814,6 +814,7 @@ static int snd_sb_csp_start(struct snd_s mixR = snd_sbmixer_read(p->chip, SB_DSP4_PCM_DEV + 1); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV, mixL & 0x7); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV + 1, mixR & 0x7); + spin_unlock_irqrestore(&p->chip->mixer_lock, flags); spin_lock(&p->chip->reg_lock); set_mode_register(p->chip, 0xc0); /* c0 = STOP */
@@ -853,6 +854,7 @@ static int snd_sb_csp_start(struct snd_s spin_unlock(&p->chip->reg_lock); /* restore PCM volume */ + spin_lock_irqsave(&p->chip->mixer_lock, flags); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV, mixL); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV + 1, mixR); spin_unlock_irqrestore(&p->chip->mixer_lock, flags);
@@ -878,6 +880,7 @@ static int snd_sb_csp_stop(struct snd_sb mixR = snd_sbmixer_read(p->chip, SB_DSP4_PCM_DEV + 1); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV, mixL & 0x7); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV + 1, mixR & 0x7); + spin_unlock_irqrestore(&p->chip->mixer_lock, flags); spin_lock(&p->chip->reg_lock); if (p->running & SNDRV_SB_CSP_ST_QSOUND) {
@@ -892,6 +895,7 @@ static int snd_sb_csp_stop(struct snd_sb spin_unlock(&p->chip->reg_lock); /* restore PCM volume */ + spin_lock_irqsave(&p->chip->mixer_lock, flags); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV, mixL); snd_sbmixer_write(p->chip, SB_DSP4_PCM_DEV + 1, mixR); spin_unlock_irqrestore(&p->chip->mixer_lock, flags);