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    Subject[PATCH 3.13 161/172] dma: ste_dma40: dont dereference free:d descriptor
    Date
    3.13-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Linus Walleij <linus.walleij@linaro.org>

    commit e9baa9d9d520fb0e24cca671e430689de2d4a4b2 upstream.

    It appears that in the DMA40 driver the DMA tasklet will very
    often dereference memory for a descriptor just free:d from the
    DMA40 slab. Nothing happens because no other part of the driver
    has yet had a chance to claim this memory, but it's really
    nasty to dereference free:d memory, so let's check the flag
    before the descriptor is free and store it in a bool variable.

    Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
    Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
    Signed-off-by: Vinod Koul <vinod.koul@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/dma/ste_dma40.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/drivers/dma/ste_dma40.c
    +++ b/drivers/dma/ste_dma40.c
    @@ -1641,6 +1641,7 @@ static void dma_tasklet(unsigned long da
    struct d40_chan *d40c = (struct d40_chan *) data;
    struct d40_desc *d40d;
    unsigned long flags;
    + bool callback_active;
    dma_async_tx_callback callback;
    void *callback_param;

    @@ -1668,6 +1669,7 @@ static void dma_tasklet(unsigned long da
    }

    /* Callback to client */
    + callback_active = !!(d40d->txd.flags & DMA_PREP_INTERRUPT);
    callback = d40d->txd.callback;
    callback_param = d40d->txd.callback_param;

    @@ -1690,7 +1692,7 @@ static void dma_tasklet(unsigned long da

    spin_unlock_irqrestore(&d40c->lock, flags);

    - if (callback && (d40d->txd.flags & DMA_PREP_INTERRUPT))
    + if (callback_active && callback)
    callback(callback_param);

    return;



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