In _malloc_init(), round up the region being mprotected RW to the malloc

page size, rather than relying upon mprotect to round up to the actual mmu
page size.

This repairs malloc operation on systems where the malloc page size
(1 << _MAX_PAGE_SHIFT) is larger than the mmu page size.

ok otto@

diff --git a/lib/libc/stdlib/malloc.c b/lib/libc/stdlib/malloc.c
index b5eb212..17ba5fb 100644 (file)
--- a/lib/libc/stdlib/malloc.c
+++ b/lib/libc/stdlib/malloc.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: malloc.c,v 1.295 2023/12/19 06:59:28 otto Exp $       */
+/*     $OpenBSD: malloc.c,v 1.296 2024/03/30 07:50:39 miod Exp $       */
 /*
  * Copyright (c) 2008, 2010, 2011, 2016, 2023 Otto Moerbeek <otto@drijf.net>
  * Copyright (c) 2012 Matthew Dempsky <matthew@openbsd.org>
@@ -1428,7 +1428,7 @@ _malloc_init(int from_rthreads)
        }
        if (!mopts.malloc_canary) {
                char *p;
-               size_t sz, d_avail;
+               size_t sz, roundup_sz, d_avail;
 
                omalloc_init();
                /*
@@ -1436,20 +1436,20 @@ _malloc_init(int from_rthreads)
                 * randomise offset inside the page at which the dir_infos
                 * lay (subject to alignment by 1 << MALLOC_MINSHIFT)
                 */
-               sz = mopts.malloc_mutexes * sizeof(*d) + 2 * MALLOC_PAGESIZE;
-               if ((p = MMAPNONE(sz, 0)) == MAP_FAILED)
+               sz = mopts.malloc_mutexes * sizeof(*d);
+               roundup_sz = (sz + MALLOC_PAGEMASK) & ~MALLOC_PAGEMASK;
+               if ((p = MMAPNONE(roundup_sz + 2 * MALLOC_PAGESIZE, 0)) ==
+                   MAP_FAILED)
                        wrterror(NULL, "malloc_init mmap1 failed");
-               if (mprotect(p + MALLOC_PAGESIZE, mopts.malloc_mutexes *
-                   sizeof(*d), PROT_READ | PROT_WRITE))
+               if (mprotect(p + MALLOC_PAGESIZE, roundup_sz,
+                   PROT_READ | PROT_WRITE))
                        wrterror(NULL, "malloc_init mprotect1 failed");
-               if (mimmutable(p, sz))
+               if (mimmutable(p, roundup_sz + 2 * MALLOC_PAGESIZE))
                        wrterror(NULL, "malloc_init mimmutable1 failed");
-               d_avail = (((mopts.malloc_mutexes * sizeof(*d) +
-                   MALLOC_PAGEMASK) & ~MALLOC_PAGEMASK) -
-                   (mopts.malloc_mutexes * sizeof(*d))) >> MALLOC_MINSHIFT;
+               d_avail = (roundup_sz - sz) >> MALLOC_MINSHIFT;
                d = (struct dir_info *)(p + MALLOC_PAGESIZE +
                    (arc4random_uniform(d_avail) << MALLOC_MINSHIFT));
-               STATS_ADD(d[1].malloc_used, sz);
+               STATS_ADD(d[1].malloc_used, roundup_sz + 2 * MALLOC_PAGESIZE);
                for (i = 0; i < mopts.malloc_mutexes; i++)
                        mopts.malloc_pool[i] = &d[i];
                mopts.internal_funcs = 1;