[PATCH 3.12 004/118] ALSA: memalloc.h - fix wrong truncation of dma_addr_t

Greg Kroah-Hartman
2013-12-18T21:13:18Z

From: Stefano Panella <stefano.panella@citrix.com>

commit 932e9dec380c67ec15ac3eb073bb55797d8b4801 upstream.

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: Stefano Panella <stefano.panella@citrix.com>
Reviewed-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/sound/memalloc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/sound/memalloc.h
+++ b/include/sound/memalloc.h
@@ -103,7 +103,7 @@ static inline dma_addr_t snd_sgbuf_get_a
{
struct snd_sg_buf *sgbuf = dmab->private_data;
dma_addr_t addr = sgbuf->table[offset >> PAGE_SHIFT].addr;
- addr &= PAGE_MASK;
+ addr &= ~((dma_addr_t)PAGE_SIZE - 1);
return addr + offset % PAGE_SIZE;
}