[clang] [Clang] Fix potential null pointer dereference in retain cycle detection (PR #95192)

[via cfe-commits]

https://github.com/smanna12 updated https://github.com/llvm/llvm-project/pull/95192

>From 6852bd6773c13dd9e573df460e74e2b7306c63f0 Mon Sep 17 00:00:00 2001
From: "Manna, Soumi" <soumi.manna at intel.com>
Date: Tue, 11 Jun 2024 19:52:03 -0700
Subject: [PATCH 1/3] [Clang] Fix potential null pointer dereference in retain
 cycle detection

This patch resolves a static analyzer bug where `S.getCurMethodDecl()` could return `nullptr` when calling getSelfDecl(() and was being dereferenced without a null check. The fix introduces a check for a non-null return value before accessing `getSelfDecl()` to ensure safe dereferencing.

This change prevents undefined behavior in scenarios where the current method declaration is not available, thus enhancing the robustness of the retain cycle detection logic.
---
 clang/lib/Sema/SemaObjC.cpp | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/clang/lib/Sema/SemaObjC.cpp b/clang/lib/Sema/SemaObjC.cpp
index d396258cfc7d1..69c78f034bd43 100644
--- a/clang/lib/Sema/SemaObjC.cpp
+++ b/clang/lib/Sema/SemaObjC.cpp
@@ -848,12 +848,16 @@ static bool findRetainCycleOwner(Sema &S, Expr *e, RetainCycleOwner &owner) {
 
       owner.Indirect = true;
       if (pre->isSuperReceiver()) {
-        owner.Variable = S.getCurMethodDecl()->getSelfDecl();
-        if (!owner.Variable)
+        if (const auto *CurMethodDecl = S.getCurMethodDecl()) {
+          owner.Variable = CurMethodDecl()->getSelfDecl();
+          if (!owner.Variable)
+            return false;
+          owner.Loc = pre->getLocation();
+          owner.Range = pre->getSourceRange();
+          return true;
+        } else {
           return false;
-        owner.Loc = pre->getLocation();
-        owner.Range = pre->getSourceRange();
-        return true;
+        }
       }
       e = const_cast<Expr *>(
           cast<OpaqueValueExpr>(pre->getBase())->getSourceExpr());

>From dcf371b72e3d1fbfdeaa6658aebdcdabc7b6f4ae Mon Sep 17 00:00:00 2001
From: "Manna, Soumi" <soumi.manna at intel.com>
Date: Tue, 11 Jun 2024 20:08:45 -0700
Subject: [PATCH 2/3] Fix build errors

---
 clang/lib/Sema/SemaObjC.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaObjC.cpp b/clang/lib/Sema/SemaObjC.cpp
index 69c78f034bd43..65e297b3b1249 100644
--- a/clang/lib/Sema/SemaObjC.cpp
+++ b/clang/lib/Sema/SemaObjC.cpp
@@ -849,7 +849,7 @@ static bool findRetainCycleOwner(Sema &S, Expr *e, RetainCycleOwner &owner) {
       owner.Indirect = true;
       if (pre->isSuperReceiver()) {
         if (const auto *CurMethodDecl = S.getCurMethodDecl()) {
-          owner.Variable = CurMethodDecl()->getSelfDecl();
+          owner.Variable = CurMethodDecl->getSelfDecl();
           if (!owner.Variable)
             return false;
           owner.Loc = pre->getLocation();

>From 969d0a85dd0516e914b4d9fad00c9350f5009a2e Mon Sep 17 00:00:00 2001
From: "Manna, Soumi" <soumi.manna at intel.com>
Date: Tue, 11 Jun 2024 21:18:28 -0700
Subject: [PATCH 3/3] Add new bug

---
 clang/lib/Sema/SemaObjC.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Sema/SemaObjC.cpp b/clang/lib/Sema/SemaObjC.cpp
index 65e297b3b1249..4b951ea536034 100644
--- a/clang/lib/Sema/SemaObjC.cpp
+++ b/clang/lib/Sema/SemaObjC.cpp
@@ -1173,9 +1173,13 @@ void SemaObjC::checkRetainCycles(ObjCMessageExpr *msg) {
       return;
   } else {
     assert(msg->getReceiverKind() == ObjCMessageExpr::SuperInstance);
-    owner.Variable = SemaRef.getCurMethodDecl()->getSelfDecl();
-    owner.Loc = msg->getSuperLoc();
-    owner.Range = msg->getSuperLoc();
+    if (const auto *CurMethodDecl = SemaRef.getCurMethodDecl()) {
+      owner.Variable = CurMethodDecl->getSelfDecl();
+      owner.Loc = msg->getSuperLoc();
+      owner.Range = msg->getSuperLoc();
+    } else {
+      return;
+    }
   }
 
   // Check whether the receiver is captured by any of the arguments.