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[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.

llvm-svn: 318901
This commit is contained in:
Alexander Potapenko 2017-11-23 08:34:32 +00:00
parent 270ced2bce
commit 391804f54b
2 changed files with 23 additions and 2 deletions
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3
llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
View File

@ -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()));

22
llvm/test/Instrumentation/MemorySanitizer/check_access_address.ll
View File

@ -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