Merge pull request #162 from struct/tags_12_3_22

Comment and null ptr checks

Author: struct

Makefile

@@ -14,7 +14,8 @@ SECURITY_FLAGS = -DSANITIZE_CHUNKS=0 -DFUZZ_MODE=0 -DPERM_FREE_REALLOC=0 -DDISAB
 
 ## Enable memory tagging support. This will generate a random
 ## 1 byte tag per addressable chunk of memory. These tags can
-## be retrieved and verified
+## be retrieved and verified. This feature will likely interfere
+## with ARM MTE and PAC. See MEMORY_TAGGING.md for more information
 MEMORY_TAGGING = -DMEMORY_TAGGING=0
 
 ## Enable abort() when isoalloc can't gather enough entropy.

src/iso_alloc.c

@@ -1464,13 +1464,13 @@ INTERNAL_HIDDEN void iso_free_chunk_from_zone(iso_alloc_zone_t *zone, void *rest
 }
 
 INTERNAL_HIDDEN void _iso_free_from_zone(void *p, iso_alloc_zone_t *zone, bool permanent) {
-    if(p == NULL) {
+    if(p == NULL || zone == NULL) {
         return;
     }
 
 #if MEMORY_TAGGING
     /* Its possible that we were passed a tagged pointer */
-    if(UNLIKELY(zone != NULL && zone->tagged == true && ((uintptr_t) p & IS_TAGGED_PTR_MASK) != 0)) {
+    if(UNLIKELY(zone->tagged == true && ((uintptr_t) p & IS_TAGGED_PTR_MASK) != 0)) {
         /* If the untagging results in a bad pointer we
          * will catch it in the free path and abort */
         p = _untag_ptr(p, zone);