[gentoo-commits] proj/sandbox:master commit in: libsandbox/

[Mike Gilbert]

commit:     aaaf1052ff7bed04feece2a1d865974eb578ef57
Author:     Mike Gilbert <floppym <AT> gentoo <DOT> org>
AuthorDate: Sat Mar  8 19:30:13 2025 +0000
Commit:     Mike Gilbert <floppym <AT> gentoo <DOT> org>
CommitDate: Sat Mar  8 19:36:04 2025 +0000
URL:        https://gitweb.gentoo.org/proj/sandbox.git/commit/?id=aaaf1052

libsandbox: fix pagesize rounding

Signed-off-by: Mike Gilbert <floppym <AT> gentoo.org>

 libsandbox/memory.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/libsandbox/memory.c b/libsandbox/memory.c
index 1446116..c861fbc 100644
--- a/libsandbox/memory.c
+++ b/libsandbox/memory.c
@@ -53,15 +53,16 @@ static void *sb_mremap(void *old_address, size_t old_size, 
size_t new_size, int
 #define ALIGN_FACTOR 2
 #define ALIGN_SIZE (ALIGN_FACTOR * sizeof(size_t))
 
-void *malloc(size_t size)
+static size_t round_to_page(size_t size)
 {
        long pagesize = sysconf(_SC_PAGESIZE);
+       size_t remainder = size % pagesize;
+       return remainder ? size + pagesize - remainder : size;
+}
 
-       if (__builtin_add_overflow(size, ALIGN_SIZE, &size) ||
-                       __builtin_add_overflow(size, pagesize - size % 
pagesize, &size)) {
-               errno = ENOMEM;
-               return NULL;
-       }
+void *malloc(size_t size)
+{
+       size = round_to_page(size + ALIGN_SIZE);
 
        size_t *sp = mmap(0, size, PROT_READ|PROT_WRITE, 
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
        if (sp == MAP_FAILED)
@@ -103,18 +104,13 @@ void *realloc(void *ptr, size_t size)
 {
        if (ptr == NULL)
                return malloc(size);
+
        if (size == 0) {
                free(ptr);
                return NULL;
        }
 
-       long pagesize = sysconf(_SC_PAGESIZE);
-
-       if (__builtin_add_overflow(size, ALIGN_SIZE, &size) ||
-                       __builtin_add_overflow(size, pagesize - size % 
pagesize, &size)) {
-               errno = ENOMEM;
-               return NULL;
-       }
+       size = round_to_page(size + ALIGN_SIZE);
 
        size_t *sp = ptr;
        sp -= 2;