• Stefano Panella's avatar
    ALSA: memalloc.h - fix wrong truncation of dma_addr_t · 932e9dec
    Stefano Panella authored
    When running a 32bit kernel the hda_intel driver is still reporting
    a 64bit dma_mask if the HW supports it.
    
    From sound/pci/hda/hda_intel.c:
    
            /* allow 64bit DMA address if supported by H/W */
            if ((gcap & ICH6_GCAP_64OK) && !pci_set_dma_mask(pci, DMA_BIT_MASK(64)))
                    pci_set_consistent_dma_mask(pci, DMA_BIT_MASK(64));
            else {
                    pci_set_dma_mask(pci, DMA_BIT_MASK(32));
                    pci_set_consistent_dma_mask(pci, DMA_BIT_MASK(32));
            }
    
    which means when there is a call to dma_alloc_coherent from
    snd_malloc_dev_pages a machine address bigger than 32bit can be returned.
    This can be true in particular if running  the 32bit kernel as a pv dom0
    under the Xen Hypervisor or PAE on bare metal.
    
    The problem is that when calling setup_bdle to program the BLE the
    dma_addr_t returned from the dma_alloc_coherent is wrongly truncated
    from snd_sgbuf_get_addr if running a 32bit kernel:
    
    static inline dma_addr_t snd_sgbuf_get_addr(struct snd_dma_buffer *dmab,
                                               size_t offset)
    {
            struct snd_sg_buf *sgbuf = dmab->private_data;
            dma_addr_t addr = sgbuf->table[offset >> PAGE_SHIFT].addr;
            addr &= PAGE_MASK;
            return addr + offset % PAGE_SIZE;
    }
    
    where PAGE_MASK in a 32bit kernel is zeroing the upper 32bit af addr.
    
    Without this patch the HW will fetch the 32bit truncated address,
    which is not the one obtained from dma_alloc_coherent and will result
    to a non working audio but can corrupt host memory at a random location.
    
    The current patch apply to v3.13-rc3-74-g6c843f5
    Signed-off-by: default avatarStefano Panella <stefano.panella@citrix.com>
    Reviewed-by: default avatarFrediano Ziglio <frediano.ziglio@citrix.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
    932e9dec
memalloc.h 4.68 KB