On 12/17/20 11:14 AM, Takashi Iwai wrote:
On Thu, 17 Dec 2020 10:55:42 +0100,
Takashi Iwai wrote:
On Thu, 17 Dec 2020 10:43:45 +0100,
Lars-Peter Clausen wrote:
On 12/17/20 5:15 PM, Robin Gong wrote:
Since mmap for userspace is based on page alignment, add page alignment
for iram alloc from pool, otherwise, some good data located in the same
page of dmab->area maybe touched wrongly by userspace like pulseaudio.
I wonder, do we also have to align size to be a multiple of PAGE_SIZE
to avoid leaking unrelated data?
Hm, a good question. Basically the PCM buffer size itself shouldn't
be influenced by that (i.e. no hw-constraint or such is needed), but
the padding should be cleared indeed. I somehow left those to the
allocator side, but maybe it's safer to clear the whole buffer in
sound/core/memalloc.c commonly.
That said, something like below (totally untested).
We might pass the pass-aligned size to dmab->bytes field instead of
keeping the original value, too.
We'd need this for those APIs that also pass the size to the free()
function. Like dma_free_coherent() and free_pages_exact(), but maybe
those round up internally as well.
I had a quick look and I could not find any place were the code relies
on the requested buffer size being stored in dmab->bytes. In fact we
already reuse the buffer if there is an allocated buffer that is larger
than the requested buffer (See snd_pcm_lib_malloc_pages), so this should
be OK.
Takashi
---
--- a/sound/core/memalloc.c
+++ b/sound/core/memalloc.c
@@ -126,6 +126,7 @@ static inline gfp_t snd_mem_get_gfp_flags(const struct
device *dev,
int snd_dma_alloc_pages(int type, struct device *device, size_t size,
struct snd_dma_buffer *dmab)
{
+ size_t orig_size = size;
gfp_t gfp;
if (WARN_ON(!size))
@@ -133,6 +134,7 @@ int snd_dma_alloc_pages(int type, struct device *device,
size_t size,
if (WARN_ON(!dmab))
return -ENXIO;
+ size = PAGE_ALIGN(size);
dmab->dev.type = type;
dmab->dev.dev = device;
dmab->bytes = 0;
@@ -177,7 +179,8 @@ int snd_dma_alloc_pages(int type, struct device *device,
size_t size,
}
if (! dmab->area)
return -ENOMEM;
- dmab->bytes = size;
+ memset(dmab->area, 0, size);
+ dmab->bytes = orig_size;
return 0;
}
EXPORT_SYMBOL(snd_dma_alloc_pages);
