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    Subject[PATCH 5.15 049/917] ALSA: PCM: Fix NULL dereference at mmap checks
    Date
    From: Takashi Iwai <tiwai@suse.de>

    commit 8e537d5dec34cac746dd6abf6a83e5de3aa471fc upstream.

    The recent refactoring of mmap handling caused Oops on some devices
    that don't use the standard memory allocations. This patch addresses
    it by allowing snd_dma_buffer_mmap() helper to receive the NULL
    pointer dmab argument (and return an error appropriately).

    Fixes: a202bd1ad86d ("ALSA: core: Move mmap handler into memalloc ops")
    Cc: <stable@vger.kernel.org>
    Link: https://lore.kernel.org/r/20211107163911.13534-1-tiwai@suse.de
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    sound/core/memalloc.c | 5 ++++-
    1 file changed, 4 insertions(+), 1 deletion(-)

    --- a/sound/core/memalloc.c
    +++ b/sound/core/memalloc.c
    @@ -176,8 +176,11 @@ EXPORT_SYMBOL_GPL(snd_devm_alloc_pages);
    int snd_dma_buffer_mmap(struct snd_dma_buffer *dmab,
    struct vm_area_struct *area)
    {
    - const struct snd_malloc_ops *ops = snd_dma_get_ops(dmab);
    + const struct snd_malloc_ops *ops;

    + if (!dmab)
    + return -ENOENT;
    + ops = snd_dma_get_ops(dmab);
    if (ops && ops->mmap)
    return ops->mmap(dmab, area);
    else

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