[PATCH] tools/nolibc/stdlib: fix memory error in realloc()

[Brennan Xavier McManus]

Pass user_p_len to memcpy() instead of heap->len to prevent realloc()
from copying an extra sizeof(heap) bytes from beyond the allocated
region.

Signed-off-by: Brennan Xavier McManus <bxmcmanus@xxxxxxxxx>
---

All tests from Ammar's original test program pass:
https://gist.github.com/ammarfaizi2/db0af6aa0b95a0c7478bce64e349f021
This fix was tested with the following added test for realloc():
https://github.com/brennan913/nolibc-test/blob/main/nolibc_test.c#L73-L120

 tools/include/nolibc/stdlib.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h
index bacfd35c5156..5be9d3c7435a 100644
--- a/tools/include/nolibc/stdlib.h
+++ b/tools/include/nolibc/stdlib.h
@@ -185,7 +185,7 @@ void *realloc(void *old_ptr, size_t new_size)
 	if (__builtin_expect(!ret, 0))
 		return NULL;
 
-	memcpy(ret, heap->user_p, heap->len);
+	memcpy(ret, heap->user_p, user_p_len);
 	munmap(heap, heap->len);
 	return ret;
 }
-- 
2.39.2