[patch v1] malloc: set NON_MAIN_ARENA flag for reclaimed memalign chunk (BZ #30101)

[DJ Delorie <dj@redhat.com>]

From 61bd502ecac4d63f04c74bfc491ca675660d26b7 Mon Sep 17 00:00:00 2001
From: DJ Delorie <dj@redhat.com>
Date: Mon, 3 Apr 2023 17:33:03 -0400
Subject: malloc: set NON_MAIN_ARENA flag for reclaimed memalign chunk (BZ #30101)

Based on these comments in malloc.c:

   size field is or'ed with NON_MAIN_ARENA if the chunk was obtained
   from a non-main arena.  This is only set immediately before handing
   the chunk to the user, if necessary.

   The NON_MAIN_ARENA flag is never set for unsorted chunks, so it
   does not have to be taken into account in size comparisons.

When we pull a chunk off the unsorted list (or any list) we need to
make sure that flag is set properly before returning the chunk.

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 0315ac5d16..66e7ca57dd 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5147,6 +5147,8 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
       p = victim;
       m = chunk2mem (p);
       set_inuse (p);
+      if (av != &main_arena)
+	set_non_main_arena (p);
     }
   else
     {