[Python-checkins] r87834 - in python/branches/py3k: Misc/ACKS Misc/NEWS Objects/obmalloc.c
antoine.pitrou
python-checkins at python.org
Fri Jan 7 22:44:05 CET 2011
Author: antoine.pitrou
Date: Fri Jan 7 22:43:59 2011
New Revision: 87834
Log:
Issue #8020: Avoid a crash where the small objects allocator would read
non-Python managed memory while it is being modified by another thread.
Patch by Matt Bandy.
Modified:
python/branches/py3k/Misc/ACKS
python/branches/py3k/Misc/NEWS
python/branches/py3k/Objects/obmalloc.c
Modified: python/branches/py3k/Misc/ACKS
==============================================================================
--- python/branches/py3k/Misc/ACKS (original)
+++ python/branches/py3k/Misc/ACKS Fri Jan 7 22:43:59 2011
@@ -46,6 +46,7 @@
Greg Ball
Luigi Ballabio
Jeff Balogh
+Matt Bandy
Michael J. Barber
Chris Barker
Nick Barnes
Modified: python/branches/py3k/Misc/NEWS
==============================================================================
--- python/branches/py3k/Misc/NEWS (original)
+++ python/branches/py3k/Misc/NEWS Fri Jan 7 22:43:59 2011
@@ -36,6 +36,10 @@
Library
-------
+- Issue #8020: Avoid a crash where the small objects allocator would read
+ non-Python managed memory while it is being modified by another thread.
+ Patch by Matt Bandy.
+
- Issue #10827: Changed the rules for 2-digit years. The time.asctime
function will now format any year when ``time.accept2dyear`` is
false and will accept years >= 1000 otherwise. The year range
Modified: python/branches/py3k/Objects/obmalloc.c
==============================================================================
--- python/branches/py3k/Objects/obmalloc.c (original)
+++ python/branches/py3k/Objects/obmalloc.c Fri Jan 7 22:43:59 2011
@@ -682,11 +682,19 @@
obmalloc in a small constant time, independent of the number of arenas
obmalloc controls. Since this test is needed at every entry point, it's
extremely desirable that it be this fast.
+
+Since Py_ADDRESS_IN_RANGE may be reading from memory which was not allocated
+by Python, it is important that (POOL)->arenaindex is read only once, as
+another thread may be concurrently modifying the value without holding the
+GIL. To accomplish this, the arenaindex_temp variable is used to store
+(POOL)->arenaindex for the duration of the Py_ADDRESS_IN_RANGE macro's
+execution. The caller of the macro is responsible for declaring this
+variable.
*/
#define Py_ADDRESS_IN_RANGE(P, POOL) \
- ((POOL)->arenaindex < maxarenas && \
- (uptr)(P) - arenas[(POOL)->arenaindex].address < (uptr)ARENA_SIZE && \
- arenas[(POOL)->arenaindex].address != 0)
+ ((arenaindex_temp = (POOL)->arenaindex) < maxarenas && \
+ (uptr)(P) - arenas[arenaindex_temp].address < (uptr)ARENA_SIZE && \
+ arenas[arenaindex_temp].address != 0)
/* This is only useful when running memory debuggers such as
@@ -945,6 +953,9 @@
block *lastfree;
poolp next, prev;
uint size;
+#ifndef Py_USING_MEMORY_DEBUGGER
+ uint arenaindex_temp;
+#endif
if (p == NULL) /* free(NULL) has no effect */
return;
@@ -1167,6 +1178,9 @@
void *bp;
poolp pool;
size_t size;
+#ifndef Py_USING_MEMORY_DEBUGGER
+ uint arenaindex_temp;
+#endif
if (p == NULL)
return PyObject_Malloc(nbytes);
@@ -1867,8 +1881,10 @@
int
Py_ADDRESS_IN_RANGE(void *P, poolp pool)
{
- return pool->arenaindex < maxarenas &&
- (uptr)P - arenas[pool->arenaindex].address < (uptr)ARENA_SIZE &&
- arenas[pool->arenaindex].address != 0;
+ uint arenaindex_temp = pool->arenaindex;
+
+ return arenaindex_temp < maxarenas &&
+ (uptr)P - arenas[arenaindex_temp].address < (uptr)ARENA_SIZE &&
+ arenas[arenaindex_temp].address != 0;
}
#endif
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