Merge pull request atomvm#1601 from mat-hek/upstream-fix-posix-read

Fix nif_atomvm_posix_read GC bug

We've been getting ASAN errors in the calls to `nif_atomvm_posix_read`, and it
seems it's because when GC moves things around, it also moves what the
`fd_obj_ptr` variable points to. The proposed solution is to move the GC before
`enif_get_resource`. We haven't encountered the error after the fix, but please
verify that it makes sense.

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

Author: bettio

CHANGELOG.md

@@ -63,6 +63,7 @@ memory error
 - Fix potential use after free with code generated from OTP <= 24
 - Fix `is_function/2` guard
 - Fixed segfault when calling `lists:reverse/1` (#1600)
+- Fixed nif_atomvm_posix_read GC bug
 
 ### Changed
 

src/libAtomVM/posix_nifs.c

@@ -362,14 +362,17 @@ static term nif_atomvm_posix_read(Context *ctx, int argc, term argv[])
     VALIDATE_VALUE(count_term, term_is_integer);
     int count = term_to_int(count_term);
 
+    size_t size = term_binary_data_size_in_terms(count) + BINARY_HEADER_SIZE + TERM_BOXED_SUB_BINARY_SIZE + TUPLE_SIZE(2);
+    if (UNLIKELY(memory_ensure_free_with_roots(ctx, size, argc, argv, MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
+        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
+    }
+
     void *fd_obj_ptr;
+
     if (UNLIKELY(!enif_get_resource(erl_nif_env_from_context(ctx), argv[0], glb->posix_fd_resource_type, &fd_obj_ptr))) {
         RAISE_ERROR(BADARG_ATOM);
     }
     struct PosixFd *fd_obj = (struct PosixFd *) fd_obj_ptr;
-    if (UNLIKELY(memory_ensure_free_opt(ctx, term_binary_data_size_in_terms(count) + BINARY_HEADER_SIZE + TERM_BOXED_SUB_BINARY_SIZE + TUPLE_SIZE(2), MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
-        RAISE_ERROR(OUT_OF_MEMORY_ATOM);
-    }
     term bin_term = term_create_uninitialized_binary(count, &ctx->heap, glb);
     int res = read(fd_obj->fd, (void *) term_binary_data(bin_term), count);
     if (UNLIKELY(res < 0)) {