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pcm: dshare: Fix overflow when slave_hw_ptr rolls over boundary

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In snd_pcm_dshare_sync_area() when 'slave_hw_ptr' rolls over
'slave_boundary', the wrong variable is checked ('dshare->slave_hw_ptr' vs
the local 'slave_hw_ptr'). In some cases, this results in 'slave_hw_ptr'
not rolling over correctly. 'slave_size' and 'size' are then much too
large, and the for loop blocks for several minutes copying samples.

This was likely only triggered on 32-bit systems, since the PCM boundary
is computed based on LONG_MAX and is much larger on 64-bit systems.

This same change was made to pcm_dmix in commit
6c7f60f7a9 ("Fix boundary overlap”) from
June 2005.

Signed-off-by: Brendan Shanks <brendan.shanks@teradek.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Brendan Shanks 2019-02-11 11:51:26 -08:00 • committed by Takashi Iwai
parent 4d9374e61d
commit 7cea8c1562
1 changed files with 1 additions and 1 deletions
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2
src/pcm/pcm_dshare.c
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@ -121,7 +121,7 @@ static void snd_pcm_dshare_sync_area(snd_pcm_t *pcm)
*/ */
slave_hw_ptr -= slave_hw_ptr % dshare->slave_period_size; slave_hw_ptr -= slave_hw_ptr % dshare->slave_period_size;
slave_hw_ptr += dshare->slave_buffer_size; slave_hw_ptr += dshare->slave_buffer_size;
if (dshare->slave_hw_ptr > dshare->slave_boundary) if (slave_hw_ptr >= dshare->slave_boundary)
slave_hw_ptr -= dshare->slave_boundary; slave_hw_ptr -= dshare->slave_boundary;
if (slave_hw_ptr < dshare->slave_appl_ptr) if (slave_hw_ptr < dshare->slave_appl_ptr)
slave_size = slave_hw_ptr + (dshare->slave_boundary - dshare->slave_appl_ptr); slave_size = slave_hw_ptr + (dshare->slave_boundary - dshare->slave_appl_ptr);