[aot] Fix some races if GOT entries are already set. (#18636)

decode_patch_info () would not decode patches if their corresponding GOT entry
was already set, causing half initialized MonoJumpInfo entries to be returned
to callers. Set the type of the MonoJumpInfo entry to MONO_PATCH_INFO_NONE
in these cases, and have the callers handle it.

Co-authored-by: Zoltan Varga <vargaz@gmail.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/mono/mini/aot-runtime.c b/mono/mini/aot-runtime.c
index 74ae3053f77..ca8747e78ab 100644
--- a/mono/mini/aot-runtime.c
+++ b/mono/mini/aot-runtime.c
@@ -2043,6 +2043,7 @@ init_amodule_got (MonoAotModule *amodule)
 			}
 		} else if (ji->type == MONO_PATCH_INFO_AOT_MODULE) {
 			amodule->shared_got [i] = amodule;
+		} else if (ji->type == MONO_PATCH_INFO_NONE) {
 		} else {
 			amodule->shared_got [i] = mono_resolve_patch_target (NULL, mono_get_root_domain (), NULL, ji, FALSE, error);
 			mono_error_assert_ok (error);
@@ -4031,7 +4032,8 @@ decode_patch (MonoAotModule *aot_module, MonoMemPool *mp, MonoJumpInfo *ji, guin
  * decode_patches:
  *
  *    Decode a list of patches identified by the got offsets in GOT_OFFSETS. Return an array of
- * MonoJumpInfo structures allocated from MP.
+ * MonoJumpInfo structures allocated from MP. GOT entries already loaded have their
+ * ji->type set to MONO_PATCH_INFO_NONE.
  */
 static MonoJumpInfo*
 decode_patches (MonoAotModule *amodule, MonoMemPool *mp, int n_patches, gboolean llvm, guint32 *got_offsets)
@@ -4061,6 +4063,7 @@ decode_patches (MonoAotModule *amodule, MonoMemPool *mp, int n_patches, gboolean
 		/* See load_method () for SFLDA */
 		if (got && got [got_offsets [i]] && ji->type != MONO_PATCH_INFO_SFLDA) {
 			/* Already loaded */
+			ji->type = MONO_PATCH_INFO_NONE;
 		} else {
 			res = decode_patch (amodule, mp, ji, p, &p);
 			if (!res)
@@ -4597,7 +4600,8 @@ init_method (MonoAotModule *amodule, guint32 method_index, MonoMethod *method, M
 			 * been initialized by load_method () for a static cctor before the cctor has
 			 * finished executing (#23242).
 			 */
-			if (!got [got_slots [pindex]] || ji->type == MONO_PATCH_INFO_SFLDA) {
+			if (ji->type == MONO_PATCH_INFO_NONE) {
+			} else if (!got [got_slots [pindex]] || ji->type == MONO_PATCH_INFO_SFLDA) {
 				/* In llvm-only made, we might encounter shared methods */
 				if (mono_llvm_only && ji->type == MONO_PATCH_INFO_METHOD && mono_method_check_context_used (ji->data.method)) {
 					g_assert (context);
@@ -5347,7 +5351,6 @@ load_function_full (MonoAotModule *amodule, const char *name, MonoTrampInfo **ou
 				target = mono_create_specific_trampoline (GUINT_TO_POINTER (ji->data.uindex), MONO_TRAMPOLINE_RGCTX_LAZY_FETCH, mono_get_root_domain (), NULL);
 				target = mono_create_ftnptr_malloc ((guint8 *)target);
 			} else if (ji->type == MONO_PATCH_INFO_JIT_ICALL_ADDR) {
-
 				const MonoJitICallId jit_icall_id = (MonoJitICallId)ji->data.jit_icall_id;
 				switch (jit_icall_id) {
 
@@ -5394,7 +5397,8 @@ load_function_full (MonoAotModule *amodule, const char *name, MonoTrampInfo **ou
 				g_assert (target);
 			}
 
-			amodule->got [got_slots [pindex]] = target;
+			if (ji->type != MONO_PATCH_INFO_NONE)
+				amodule->got [got_slots [pindex]] = target;
 		}
 
 		g_free (got_slots);