Avoid NULL+X UB in bss_mem.c
Fixes
@@ -254,7 +254,7 @@ static long mem_ctrl(BIO *b, int cmd, long num, void *ptr)
bm = bbm->readp;
bo = bbm->buf;
}
- off = bm->data - bo->data;
+ off = (bm->data == bo->data) ? 0 : bm->data - bo->data;
remain = bm->length;
switch (cmd) {
@@ -277,7 +277,7 @@ static long mem_ctrl(BIO *b, int cmd, long num, void *ptr)
if (num < 0 || num > off + remain)
return -1; /* Can't see outside of the current buffer */
- bm->data = bo->data + num;
+ bm->data = (num != 0) ? bo->data + num : bo->data;
bm->length = bo->length - num;
bm->max = bo->max - num;
off = num;
