[PATCH 3.2 130/185] ALSA: memalloc.h - fix wrong truncation ofdma_addr_t

From: Ben Hutchings
Date: Sat Dec 28 2013 - 21:47:13 EST

3.2.54-rc1 review patch. If anyone has any objections, please let me know.


From: Stefano Panella <stefano.panella@xxxxxxxxxx>

commit 932e9dec380c67ec15ac3eb073bb55797d8b4801 upstream.

When running a 32bit kernel the hda_intel driver is still reporting
a 64bit dma_mask if the HW supports it.


/* 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@xxxxxxxxxx>
Reviewed-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
include/sound/memalloc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/sound/memalloc.h
+++ b/include/sound/memalloc.h
@@ -101,7 +101,7 @@ static inline unsigned int snd_sgbuf_ali
static inline dma_addr_t snd_sgbuf_get_addr(struct snd_sg_buf *sgbuf, size_t offset)
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;

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