[scudo] allocation_ring_buffer_size <= 0 disables buffer

[fmayer]

Prevent a null pointer exception for allocation_ring_buffer_size < 0.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Florian Mayer (fmayer)

Changes

Prevent a null pointer exception for allocation_ring_buffer_size < 0.

---

Full diff: https://github.com/llvm/llvm-project/pull/71791.diff

2 Files Affected:

• (modified) compiler-rt/lib/scudo/standalone/combined.h (+1-1)
• (modified) compiler-rt/lib/scudo/standalone/flags.inc (+2-1)

diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
index b1700e5ecef7f5b..cb48c8c1e3a1e77 100644
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -886,7 +886,7 @@ class Allocator {
 
   void setTrackAllocationStacks(bool Track) {
     initThreadMaybe();
-    if (getFlags()->allocation_ring_buffer_size == 0) {
+    if (getFlags()->allocation_ring_buffer_size <= 0) {
       DCHECK(!Primary.Options.load().get(OptionBit::TrackAllocationStacks));
       return;
     }
diff --git a/compiler-rt/lib/scudo/standalone/flags.inc b/compiler-rt/lib/scudo/standalone/flags.inc
index 60aeb1f1df570ac..f5a2bab5057ae13 100644
--- a/compiler-rt/lib/scudo/standalone/flags.inc
+++ b/compiler-rt/lib/scudo/standalone/flags.inc
@@ -47,4 +47,5 @@ SCUDO_FLAG(int, release_to_os_interval_ms, SCUDO_ANDROID ? INT32_MIN : 5000,
            "memory to the OS. Negative values disable the feature.")
 
 SCUDO_FLAG(int, allocation_ring_buffer_size, 32768,
-           "Entries to keep in the allocation ring buffer for scudo.")
+           "Entries to keep in the allocation ring buffer for scudo. "
+           "Values less or equal to zero disable the buffer.")

[hctim]

compiler-rt/lib/scudo/standalone/combined.h:1494

Also this (to avoid mapping it as well)?

1492   void mapAndInitializeRingBuffer() {
1493     u32 AllocationRingBufferSize =
1494         static_cast<u32>(getFlags()->allocation_ring_buffer_size);
////     Hoist this check up, and make it be |getFlags()->allocation_ring_buffer_size < 1| to avoid the
////     type punning?
1495     if (AllocationRingBufferSize < 1)
1496       return;
1497     MemMapT MemMap;
1498     MemMap.map(
1499         /*Addr=*/0U,
1500         roundUp(ringBufferSizeInBytes(AllocationRingBufferSize),

[fmayer]

compiler-rt/lib/scudo/standalone/combined.h:1494

Also this (to avoid mapping it as well)?

1492   void mapAndInitializeRingBuffer() {
1493     u32 AllocationRingBufferSize =
1494         static_cast<u32>(getFlags()->allocation_ring_buffer_size);
////     Hoist this check up, and make it be |getFlags()->allocation_ring_buffer_size < 1| to avoid the
////     type punning?
1495     if (AllocationRingBufferSize < 1)
1496       return;
1497     MemMapT MemMap;
1498     MemMap.map(
1499         /*Addr=*/0U,
1500         roundUp(ringBufferSizeInBytes(AllocationRingBufferSize),

ah, yes. thanks

[hctim]

LGTM

[fmayer]

PTAL