linux-kernel - [PATCH AUTOSEL 4.9 12/26] ALSA: sb: Fix potential double-free of CSP mixer elements

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Message-Id: <20210710023604.3172486-12-sashal@kernel.org>
Date:   Fri,  9 Jul 2021 22:35:50 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Takashi Iwai <tiwai@...e.de>, Sasha Levin <sashal@...nel.org>,
        alsa-devel@...a-project.org
Subject: [PATCH AUTOSEL 4.9 12/26] ALSA: sb: Fix potential double-free of CSP mixer elements

From: Takashi Iwai <tiwai@...e.de>

[ Upstream commit c305366a37441c2ac90b08711cb6f032b43672f2 ]

snd_sb_qsound_destroy() contains the calls of removing the previously
created mixer controls, but it doesn't clear the pointers.  As
snd_sb_qsound_destroy() itself may be repeatedly called via ioctl,
this could lead to double-free potentially.

Fix it by clearing the struct fields properly afterwards.

Link: https://lore.kernel.org/r/20210608140540.17885-4-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/isa/sb/sb16_csp.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/sound/isa/sb/sb16_csp.c b/sound/isa/sb/sb16_csp.c
index 2cc068be7d3b..90fa57ad14c0 100644
--- a/sound/isa/sb/sb16_csp.c
+++ b/sound/isa/sb/sb16_csp.c
@@ -1086,10 +1086,14 @@ static void snd_sb_qsound_destroy(struct snd_sb_csp * p)
 	card = p->chip->card;	
 	
 	down_write(&card->controls_rwsem);
-	if (p->qsound_switch)
+	if (p->qsound_switch) {
 		snd_ctl_remove(card, p->qsound_switch);
-	if (p->qsound_space)
+		p->qsound_switch = NULL;
+	}
+	if (p->qsound_space) {
 		snd_ctl_remove(card, p->qsound_space);
+		p->qsound_space = NULL;
+	}
 	up_write(&card->controls_rwsem);
 
 	/* cancel pending transfer of QSound parameters */
-- 
2.30.2