[PATCH 5.4 040/149] ALSA: sb: Fix potential double-free of CSP mixer elements

Greg Kroah-Hartman
2021-07-19T16:48:10Z

From: Takashi Iwai <tiwai@suse.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@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.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 69960cf1bb51..ef1289cc78a4 100644
--- a/sound/isa/sb/sb16_csp.c
+++ b/sound/isa/sb/sb16_csp.c
@@ -1072,10 +1072,14 @@ 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