From 1c98f574403dbcf2eb832d5535a10d967333ef2d Mon Sep 17 00:00:00 2001
From: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Date: Mon, 26 Apr 2021 06:11:29 -0700
Subject: [PATCH] ALSA: emu8000: Fix a use after free in snd_emu8000_create_mixer
Git-commit: 1c98f574403dbcf2eb832d5535a10d967333ef2d
Patch-mainline: v5.13-rc1
References: git-fixes
Our code analyzer reported a uaf.
In snd_emu8000_create_mixer, the callee snd_ctl_add(..,emu->controls[i])
calls snd_ctl_add_replace(.., kcontrol,..). Inside snd_ctl_add_replace(),
if error happens, kcontrol will be freed by snd_ctl_free_one(kcontrol).
Then emu->controls[i] points to a freed memory, and the execution comes
to __error branch of snd_emu8000_create_mixer. The freed emu->controls[i]
is used in snd_ctl_remove(card, emu->controls[i]).
My patch set emu->controls[i] to NULL if snd_ctl_add() failed to avoid
the uaf.
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210426131129.4796-1-lyl2019@mail.ustc.edu.cn
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/isa/sb/emu8000.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/sound/isa/sb/emu8000.c b/sound/isa/sb/emu8000.c
index 0aa545ac6e60..1c90421a88dc 100644
--- a/sound/isa/sb/emu8000.c
+++ b/sound/isa/sb/emu8000.c
@@ -1029,8 +1029,10 @@ snd_emu8000_create_mixer(struct snd_card *card, struct snd_emu8000 *emu)
memset(emu->controls, 0, sizeof(emu->controls));
for (i = 0; i < EMU8000_NUM_CONTROLS; i++) {
- if ((err = snd_ctl_add(card, emu->controls[i] = snd_ctl_new1(mixer_defs[i], emu))) < 0)
+ if ((err = snd_ctl_add(card, emu->controls[i] = snd_ctl_new1(mixer_defs[i], emu))) < 0) {
+ emu->controls[i] = NULL;
goto __error;
+ }
}
return 0;
--
2.26.2