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    Subject[PATCH 4.9 173/207] ALSA: gus: fix null pointer dereference on pointer block
    Date
    From: Chengfeng Ye <cyeaa@connect.ust.hk>

    [ Upstream commit a0d21bb3279476c777434c40d969ea88ca64f9aa ]

    The pointer block return from snd_gf1_dma_next_block could be
    null, so there is a potential null pointer dereference issue.
    Fix this by adding a null check before dereference.

    Signed-off-by: Chengfeng Ye <cyeaa@connect.ust.hk>
    Link: https://lore.kernel.org/r/20211024104611.9919-1-cyeaa@connect.ust.hk
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    sound/isa/gus/gus_dma.c | 2 ++
    1 file changed, 2 insertions(+)

    diff --git a/sound/isa/gus/gus_dma.c b/sound/isa/gus/gus_dma.c
    index 36c27c8323601..2e27cd3427c87 100644
    --- a/sound/isa/gus/gus_dma.c
    +++ b/sound/isa/gus/gus_dma.c
    @@ -141,6 +141,8 @@ static void snd_gf1_dma_interrupt(struct snd_gus_card * gus)
    }
    block = snd_gf1_dma_next_block(gus);
    spin_unlock(&gus->dma_lock);
    + if (!block)
    + return;
    snd_gf1_dma_program(gus, block->addr, block->buf_addr, block->count, (unsigned short) block->cmd);
    kfree(block);
    #if 0
    --
    2.33.0


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