[3.8.y.z extended stable] Patch "ALSA: memalloc.h - fix wrong truncation of dma_addr_t" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ALSA: memalloc.h - fix wrong truncation of dma_addr_t

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.16.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From a63ee0eea320efc122d0d144eeb7967936dc1e5e Mon Sep 17 00:00:00 2001
From: Stefano Panella <stefano.panella at citrix.com>
Date: Tue, 10 Dec 2013 14:20:28 +0000
Subject: ALSA: memalloc.h - fix wrong truncation of dma_addr_t

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 at citrix.com>
Reviewed-by: Frediano Ziglio <frediano.ziglio at citrix.com>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 include/sound/memalloc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/sound/memalloc.h b/include/sound/memalloc.h
index 844af65..d12356b 100644
--- a/include/sound/memalloc.h
+++ b/include/sound/memalloc.h
@@ -103,7 +103,7 @@ static inline dma_addr_t snd_sgbuf_get_addr(struct snd_dma_buffer *dmab,
 {
 	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;
 }

--
1.8.3.2