USB: EHCI: fix NULL pointer dererence in HCDs that use HCD_LOCAL_MEM
If we use the HCD_LOCAL_MEM flag and dma_declare_coherent_memory() to enforce the host controller's local memory utilization we also need to disable native scatter-gather support, otherwise hcd_alloc_coherent() in map_urb_for_dma() is called with urb->transfer_buffer == NULL, that triggers a NULL pointer dereference. We can also consider to add a WARN_ON() and return an error code to better catch this problem in the future. At the moment no driver seems to hit this bug, so I should consider this a low-priority fix. Signed-off-by: Andrea Righi <arighi@develer.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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