fix calloc when __simple_malloc implementation is used

previously, calloc's implementation encoded assumptions about the
implementation of malloc, accessing a size_t word just prior to the
allocated memory to determine if it was obtained by mmap to optimize
out the zero-filling. when __simple_malloc is used (static linking a
program with no realloc/free), it doesn't matter if the result of this
check is wrong, since all allocations are zero-initialized anyway. but
the access could be invalid if it crosses a page boundary or if the
pointer is not sufficiently aligned, which can happen for very small
allocations.

this patch fixes the issue by moving the zero-fill logic into malloc.c
with the full malloc, as a new function named __malloc0, which is
provided by a weak alias to __simple_malloc (which always gives
zero-filled memory) when the full malloc is not in use.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/malloc/lite_malloc.c b/src/malloc/lite_malloc.c
index 008549d6..b09f30b0 100644
--- a/src/malloc/lite_malloc.c
+++ b/src/malloc/lite_malloc.c
@@ -47,3 +47,4 @@ void *__simple_malloc(size_t n)
 }
 
 weak_alias(__simple_malloc, malloc);
+weak_alias(__simple_malloc, malloc0);