commit 1cdac61065e72db60d26e03ef9286d2743d7000e
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Thu Oct 21 08:39:58 2021 -0700
committer GitHub <noreply@github.com> Thu Oct 21 08:39:58 2021 -0700
tree b118974db71db92f73df741a6373c5682baa8e6a
parent 00ddc1fbd7296ffe066077194a895b175cca26de

bpo-45521: Fix a bug in the obmalloc radix tree code. (GH-29051) (GH-29122)

MAP_BOT_LENGTH was incorrectly used to compute MAP_TOP_MASK instead of
MAP_TOP_LENGTH. On 64-bit machines, the error causes the tree to hold
46-bits of virtual addresses, rather than the intended 48-bits.
(cherry picked from commit 311910b31a4bd94dc79298388b7cb65ca5546438)

Objects/obmalloc.c

diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 15c442b..615703a 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -1328,7 +1328,7 @@ _Py_GetAllocatedBlocks(void)
 
 #define MAP_TOP_BITS INTERIOR_BITS
 #define MAP_TOP_LENGTH (1 << MAP_TOP_BITS)
-#define MAP_TOP_MASK (MAP_BOT_LENGTH - 1)
+#define MAP_TOP_MASK (MAP_TOP_LENGTH - 1)
 
 #define MAP_MID_BITS INTERIOR_BITS
 #define MAP_MID_LENGTH (1 << MAP_MID_BITS)