[Python-checkins] cpython: Issue #1621: Avoid signed int negation overflow in audioop

[martin.panter]

https://hg.python.org/cpython/rev/d6a86018ab33
changeset:   102404:d6a86018ab33
user:        Martin Panter <vadmium+py at gmail.com>
date:        Tue Jul 19 03:05:42 2016 +0000
summary:
  Issue #1621: Avoid signed int negation overflow in audioop

files:
  Misc/NEWS         |  2 ++
  Modules/audioop.c |  4 +++-
  2 files changed, 5 insertions(+), 1 deletions(-)


diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -26,6 +26,8 @@
 Library
 -------
 
+- Issue #1621: Avoid signed int negation overflow in the "audioop" module.
+
 - Issue #27533: Release GIL in nt._isdir
 
 - Issue #17711: Fixed unpickling by the persistent ID with protocol 0.
diff --git a/Modules/audioop.c b/Modules/audioop.c
--- a/Modules/audioop.c
+++ b/Modules/audioop.c
@@ -446,7 +446,9 @@
         return NULL;
     for (i = 0; i < fragment->len; i += width) {
         int val = GETRAWSAMPLE(width, fragment->buf, i);
-        if (val < 0) absval = (-val);
+        /* Cast to unsigned before negating. Unsigned overflow is well-
+        defined, but signed overflow is not. */
+        if (val < 0) absval = -(unsigned int)val;
         else absval = val;
         if (absval > max) max = absval;
     }

-- 
Repository URL: https://hg.python.org/cpython