From: Florian Weimer <fweimer@redhat.com>
Date: Thu, 13 Oct 2022 03:45:41 +0000 (+0200)
Subject: malloc: Switch global_max_fast to uint8_t
X-Git-Tag: glibc-2.37~260
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=15a94e6668a6d7c5697e805d8d67f1d102d0d52e;p=thirdparty%2Fglibc.git

malloc: Switch global_max_fast to uint8_t

MAX_FAST_SIZE is 160 at most, so a uint8_t is sufficient.  This makes
it harder to use memory corruption, by overwriting global_max_fast
with a large value, to fundamentally alter malloc behavior.

Reviewed-by: DJ Delorie <dj@redhat.com>
---

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 953183e9567..2a61c8b5ee3 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1757,7 +1757,7 @@ typedef struct malloc_chunk *mfastbinptr;
 #define set_contiguous(M)      ((M)->flags &= ~NONCONTIGUOUS_BIT)
 
 /* Maximum size of memory handled in fastbins.  */
-static INTERNAL_SIZE_T global_max_fast;
+static uint8_t global_max_fast;
 
 /*
    Set value of max_fast.