From: Lv Yunlong lyl2019@mail.ustc.edu.cn
commit 1c98f574403dbcf2eb832d5535a10d967333ef2d upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/isa/sb/emu8000.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/sound/isa/sb/emu8000.c +++ b/sound/isa/sb/emu8000.c @@ -1042,8 +1042,10 @@ snd_emu8000_create_mixer(struct snd_card
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;