[03/66] ALSA: sb: Fix potential double-free of CSP mixer elements

Message ID 20210608140540.17885-4-tiwai@suse.de
State Accepted
Commit c305366a37441c2ac90b08711cb6f032b43672f2
Headers show
Series
  • ALSA: Fix assignment in if condition
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Commit Message

Takashi Iwai June 8, 2021, 2:04 p.m.
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.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/isa/sb/sb16_csp.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Patch

diff --git a/sound/isa/sb/sb16_csp.c b/sound/isa/sb/sb16_csp.c
index dec68ae6b599..5bbe6695689d 100644
--- a/sound/isa/sb/sb16_csp.c
+++ b/sound/isa/sb/sb16_csp.c
@@ -1077,10 +1077,14 @@  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 */