From: Lv Yunlong <lyl2019@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210426131129.4796-1-lyl2019@xxxxxxxxxxxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -1029,8 +1029,10 @@ 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;
