[MSan] Move the access address check before the shadow access for that address

MSan used to insert the shadow check of the store pointer operand
_after_ the shadow of the value operand has been written.
This happens to work in the userspace, as the whole shadow range is
always mapped. However in the kernel the shadow page may not exist, so
the bug may cause a crash.

This patch moves the address check in front of the shadow access.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318901 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index 459e2b39b32870a1047c22e97ed023f5f995d1a8..30b15195e8c269566a2d9019354a96ae02846771 100644 (file)
--- a/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -830,10 +830,9 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
       StoreInst *NewSI =
           IRB.CreateAlignedStore(Shadow, ShadowPtr, SI->getAlignment());
       DEBUG(dbgs() << "  STORE: " << *NewSI << "\n");
-      (void)NewSI;
 
       if (ClCheckAccessAddress)
-        insertShadowCheck(Addr, SI);
+        insertShadowCheck(Addr, NewSI);
 
       if (SI->isAtomic())
         SI->setOrdering(addReleaseOrdering(SI->getOrdering()));

diff --git a/test/Instrumentation/MemorySanitizer/check_access_address.ll b/test/Instrumentation/MemorySanitizer/check_access_address.ll
index 723d6f0cd3449c1b119ffd92dc5bc9d90c11968f..c01d3eec70c6903ac3bea98290c9215afa715c2a 100644 (file)
--- a/test/Instrumentation/MemorySanitizer/check_access_address.ll
+++ b/test/Instrumentation/MemorySanitizer/check_access_address.ll
@@ -26,3 +26,25 @@ entry:
 ; CHECK-LABEL: @ByValArgumentShadowSmallAlignment
 ; CHECK: call void @llvm.memcpy.p0i8.p0i8.i64(i8* {{.*}}, i8* {{.*}}, i64 2, i32 2, i1 false)
 ; CHECK: ret i16
+
+
+; Check instrumentation of stores. The check must precede the shadow store.
+
+define void @Store(i32* nocapture %p, i32 %x) nounwind uwtable sanitize_memory {
+entry:
+  store i32 %x, i32* %p, align 4
+  ret void
+}
+
+; CHECK-LABEL: @Store
+; CHECK: load {{.*}} @__msan_param_tls
+; CHECK: icmp
+; CHECK: br i1
+; CHECK: <label>
+; CHECK: call void @__msan_warning_noreturn
+; CHECK: <label>
+; CHECK: store
+; CHECK: store i32 %x
+; CHECK: ret void
+
+