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    Subject[PATCH AUTOSEL 5.10 54/93] ALSA: sb: Fix potential double-free of CSP mixer elements
    Date
    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 1528e04a4d28..dbcd9ab2c2b7 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
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