[PATCH 2/4] libm/stdlib: don't read past source in nano_realloc
Corinna Vinschen
vinschen@redhat.com
Wed Aug 12 08:01:19 GMT 2020
On Aug 11 16:05, Keith Packard via Newlib wrote:
> Save the computed block size and use it to avoid reading past
> the end of the source block.
>
> Signed-off-by: Keith Packard <keithp@keithp.com>
> ---
> newlib/libc/stdlib/nano-mallocr.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/newlib/libc/stdlib/nano-mallocr.c b/newlib/libc/stdlib/nano-mallocr.c
> index 04465eb9e..cef23977e 100644
> --- a/newlib/libc/stdlib/nano-mallocr.c
> +++ b/newlib/libc/stdlib/nano-mallocr.c
> @@ -466,6 +466,7 @@ void * nano_realloc(RARG void * ptr, malloc_size_t size)
> {
> void * mem;
> chunk * p_to_realloc;
> + malloc_size_t old_size;
>
> if (ptr == NULL) return nano_malloc(RCALL size);
>
> @@ -477,12 +478,15 @@ void * nano_realloc(RARG void * ptr, malloc_size_t size)
>
> /* TODO: There is chance to shrink the chunk if newly requested
> * size is much small */
> - if (nano_malloc_usable_size(RCALL ptr) >= size)
> + old_size = nano_malloc_usable_size(RCALL ptr);
> + if (old_size >= size)
> return ptr;
So, after this statement, we can be sure that size > old_size, right?
> mem = nano_malloc(RCALL size);
> if (mem != NULL)
> {
> + if (size > old_size)
...which makes this condition useless.
> + size = old_size;
> memcpy(mem, ptr, size);
why not just
memcpy(mem, ptr, old_size);
instead?
> nano_free(RCALL ptr);
> }
> --
> 2.28.0
Thanks,
Corinna
--
Corinna Vinschen
Cygwin Maintainer
Red Hat
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