[compiler-rt] 0a62c54 - [asan] Only suggest increasing poison_history_size if the buffer is full (#195732)

[via llvm-commits]

Author: Vitaly Buka
Date: 2026-05-04T23:50:43Z
New Revision: 0a62c541467eb15ebd39de379b23492e691dc965

URL: https://github.com/llvm/llvm-project/commit/0a62c541467eb15ebd39de379b23492e691dc965
DIFF: https://github.com/llvm/llvm-project/commit/0a62c541467eb15ebd39de379b23492e691dc965.diff

LOG: [asan] Only suggest increasing poison_history_size if the buffer is full (#195732)

I unlikely but possible to setup shadow state, e.g unpoison heap red
zone just after partial granule.

If buffer is not full, increasing it will not help.

Added: 
    

Modified: 
    compiler-rt/lib/asan/asan_errors.cpp
    compiler-rt/lib/asan/asan_poisoning.cpp
    compiler-rt/lib/asan/asan_poisoning.h

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/asan/asan_errors.cpp b/compiler-rt/lib/asan/asan_errors.cpp
index 802c838ee5307..cf52cd5e80136 100644
--- a/compiler-rt/lib/asan/asan_errors.cpp
+++ b/compiler-rt/lib/asan/asan_errors.cpp
@@ -662,14 +662,18 @@ static void CheckPoisonRecords(uptr addr) {
   }
 
   PoisonRecord record;
-  if (FindPoisonRecord(addr, record)) {
+  bool is_full = false;
+  if (FindPoisonRecord(addr, record, is_full)) {
     Printf("Memory was manually poisoned by thread T%u:\n", record.thread_id);
     StackTrace poison_stack = StackDepotGet(record.stack_id);
     if (poison_stack.size > 0)
       poison_stack.Print();
   } else {
     Printf("NOTE: no matching poison tracking record found.\n");
-    Printf("Try a larger value for ASAN_OPTIONS=poison_history_size=<size>.\n");
+    if (is_full) {
+      Printf(
+          "Try a larger value for ASAN_OPTIONS=poison_history_size=<size>.\n");
+    }
   }
 }
 

diff  --git a/compiler-rt/lib/asan/asan_poisoning.cpp b/compiler-rt/lib/asan/asan_poisoning.cpp
index 1da167330a0fd..7cdb8712f9592 100644
--- a/compiler-rt/lib/asan/asan_poisoning.cpp
+++ b/compiler-rt/lib/asan/asan_poisoning.cpp
@@ -19,6 +19,7 @@
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_flags.h"
 #include "sanitizer_common/sanitizer_interface_internal.h"
+#include "sanitizer_common/sanitizer_internal_defs.h"
 #include "sanitizer_common/sanitizer_libc.h"
 #include "sanitizer_common/sanitizer_ring_buffer.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
@@ -45,19 +46,20 @@ void AddPoisonRecord(const PoisonRecord &new_record) {
   poison_records->push(new_record);
 }
 
-bool FindPoisonRecord(uptr addr, PoisonRecord &match) {
+bool FindPoisonRecord(uptr addr, PoisonRecord& match, bool& is_full) {
   if (flags()->poison_history_size <= 0)
     return false;
 
   GenericScopedLock<Mutex> l(&poison_records_mutex);
 
-  if (poison_records) {
-    for (unsigned int i = 0; i < poison_records->size(); i++) {
-      PoisonRecord record = (*poison_records)[i];
-      if (record.begin <= addr && addr < record.end) {
-        internal_memcpy(&match, &record, sizeof(record));
-        return true;
-      }
+  const uptr records_count = poison_records ? poison_records->size() : 0;
+  is_full = records_count >= static_cast<uptr>(flags()->poison_history_size);
+
+  for (uptr i = 0; i < records_count; i++) {
+    PoisonRecord record = (*poison_records)[i];
+    if (record.begin <= addr && addr < record.end) {
+      internal_memcpy(&match, &record, sizeof(record));
+      return true;
     }
   }
 

diff  --git a/compiler-rt/lib/asan/asan_poisoning.h b/compiler-rt/lib/asan/asan_poisoning.h
index 4b2d6220b1b14..1490d88c5fb40 100644
--- a/compiler-rt/lib/asan/asan_poisoning.h
+++ b/compiler-rt/lib/asan/asan_poisoning.h
@@ -30,7 +30,7 @@ struct PoisonRecord {
 };
 
 void AddPoisonRecord(const PoisonRecord& new_record);
-bool FindPoisonRecord(uptr addr, PoisonRecord& match);
+bool FindPoisonRecord(uptr addr, PoisonRecord& match, bool& is_full);
 
 void AcquirePoisonRecords();
 void ReleasePoisonRecords();