dma: ste_dma40: don't dereference free:d descriptor
authorLinus Walleij <linus.walleij@linaro.org>
Thu, 13 Feb 2014 09:39:01 +0000 (10:39 +0100)
committerBen Hutchings <ben@decadent.org.uk>
Tue, 1 Apr 2014 23:58:53 +0000 (00:58 +0100)
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: Ben Hutchings <ben@decadent.org.uk>
drivers/dma/ste_dma40.c

index 13259ca..4b27c54 100644 (file)
@@ -1202,6 +1202,7 @@ static void dma_tasklet(unsigned long data)
        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;
 
@@ -1225,6 +1226,7 @@ static void dma_tasklet(unsigned long data)
        }
 
        /* Callback to client */
+       callback_active = !!(d40d->txd.flags & DMA_PREP_INTERRUPT);
        callback = d40d->txd.callback;
        callback_param = d40d->txd.callback_param;
 
@@ -1249,7 +1251,7 @@ static void dma_tasklet(unsigned long data)
 
        spin_unlock_irqrestore(&d40c->lock, flags);
 
-       if (callback && (d40d->txd.flags & DMA_PREP_INTERRUPT))
+       if (callback_active && callback)
                callback(callback_param);
 
        return;