From: Jaroslav Kysela <perex@perex.cz>
Date: Wed, 20 Mar 2013 19:37:50 +0000 (+0100)
Subject: pcm: fix and optimize snd_pcm_areas_copy function
X-Git-Tag: v1.0.27~9
X-Git-Url: https://git.alsa-project.org/?a=commitdiff_plain;h=009193a34575fe439211b9a711e56322afc7460e;p=alsa-lib.git

pcm: fix and optimize snd_pcm_areas_copy function

The memcpy() function in snd_pcm_area_copy() should not be called
with the overlapped areas. Alex discovered - using own LD_PRELOAD checked
for memcpy() input - that the memcpy() is called with src == dst.

For some special plugin combos (rate+softvol+hw for example), the same
areas with same offsets can be asked to be copied (softvol). The collapse
check uses own areas created on heap, causing dst_area == src_area &&
dst_offset == src_offset check bypassed.

Two fixes are in this patch:

- use assert to check the memcpy() input for future triggers
- bypass the snd_pcm_area_copy() call for collapsed identical areas

Reported-by: Alexander Kruppa <akruppa@gmail.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
---

diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index 5053a7bc..05737d99 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -2711,6 +2711,8 @@ int snd_pcm_area_copy(const snd_pcm_channel_area_t *dst_area, snd_pcm_uframes_t
 	    dst_area->step == (unsigned int) width) {
 		size_t bytes = samples * width / 8;
 		samples -= bytes * 8 / width;
+		assert(src < dst || src >= dst + bytes);
+		assert(dst < src || dst >= src + bytes);
 		memcpy(dst, src, bytes);
 		if (samples == 0)
 			return 0;
@@ -2845,17 +2847,21 @@ int snd_pcm_areas_copy(const snd_pcm_channel_area_t *dst_areas, snd_pcm_uframes_
 				break;
 		}
 		if (chns > 1 && chns * width == step) {
-			/* Collapse the areas */
-			snd_pcm_channel_area_t s, d;
-			s.addr = src_start->addr;
-			s.first = src_start->first;
-			s.step = width;
-			d.addr = dst_start->addr;
-			d.first = dst_start->first;
-			d.step = width;
-			snd_pcm_area_copy(&d, dst_offset * chns,
-					  &s, src_offset * chns, 
-					  frames * chns, format);
+			if (src_offset != dst_offset ||
+			    src_start->addr != dst_start->addr ||
+			    src_start->first != dst_start->first) {
+				/* Collapse the areas */
+				snd_pcm_channel_area_t s, d;
+				s.addr = src_start->addr;
+				s.first = src_start->first;
+				s.step = width;
+				d.addr = dst_start->addr;
+				d.first = dst_start->first;
+				d.step = width;
+				snd_pcm_area_copy(&d, dst_offset * chns,
+						  &s, src_offset * chns, 
+						  frames * chns, format);
+			}
 			channels -= chns;
 		} else {
 			snd_pcm_area_copy(dst_start, dst_offset,