[analyzer] Support kfree in MallocChecker

[Nathan-Huckleberry]

Summary

kmalloc is freed with kfree in the linux kernel. kmalloc support was
added in r204832, but kfree was not. Adding kfree fixes incorrectly
detected memory leaks.

[NoQ]

Whoops. Thanks!!

[Szelethus]

Nice.

clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp

class MallocChecker : public Checker<check::DeadSymbols,
                                      eval::Assume>
 {
 public:
   MallocChecker()
       : II_alloca(nullptr), II_win_alloca(nullptr), II_malloc(nullptr),
         II_free(nullptr), II_realloc(nullptr), II_calloc(nullptr),
         II_valloc(nullptr), II_reallocf(nullptr), II_strndup(nullptr),
         II_strdup(nullptr), II_win_strdup(nullptr), II_kmalloc(nullptr),
-        II_if_nameindex(nullptr), II_if_freenameindex(nullptr),
-        II_wcsdup(nullptr), II_win_wcsdup(nullptr), II_g_malloc(nullptr),
-        II_g_malloc0(nullptr), II_g_realloc(nullptr), II_g_try_malloc(nullptr),
+        II_kfree(nullptr), II_if_nameindex(nullptr),
+        II_if_freenameindex(nullptr), II_wcsdup(nullptr),
+        II_win_wcsdup(nullptr), II_g_malloc(nullptr), II_g_malloc0(nullptr),
+        II_g_realloc(nullptr), II_g_try_malloc(nullptr),
         II_g_try_malloc0(nullptr), II_g_try_realloc(nullptr),
         II_g_free(nullptr), II_g_memdup(nullptr), II_g_malloc_n(nullptr),
         II_g_malloc0_n(nullptr), II_g_realloc_n(nullptr),
         II_g_try_malloc_n(nullptr), II_g_try_malloc0_n(nullptr),
         II_g_try_realloc_n(nullptr) {}
 
   /// In pessimistic mode, the checker assumes that it does not know which
   /// functions might free the memory.
private:
   mutable std::unique_ptr<BugType> BT_BadFree[CK_NumCheckKinds];
   mutable std::unique_ptr<BugType> BT_FreeAlloca[CK_NumCheckKinds];
   mutable std::unique_ptr<BugType> BT_MismatchedDealloc;
   mutable std::unique_ptr<BugType> BT_OffsetFree[CK_NumCheckKinds];
   mutable std::unique_ptr<BugType> BT_UseZerroAllocated[CK_NumCheckKinds];
   mutable IdentifierInfo *II_alloca, *II_win_alloca, *II_malloc, *II_free,
                          *II_realloc, *II_calloc, *II_valloc, *II_reallocf,
                          *II_strndup, *II_strdup, *II_win_strdup, *II_kmalloc,
-                         *II_if_nameindex, *II_if_freenameindex, *II_wcsdup,
-                         *II_win_wcsdup, *II_g_malloc, *II_g_malloc0,
-                         *II_g_realloc, *II_g_try_malloc, *II_g_try_malloc0,
-                         *II_g_try_realloc, *II_g_free, *II_g_memdup,
-                         *II_g_malloc_n, *II_g_malloc0_n, *II_g_realloc_n,
-                         *II_g_try_malloc_n, *II_g_try_malloc0_n,
-                         *II_g_try_realloc_n;
+                         *II_kfree, *II_if_nameindex, *II_if_freenameindex,
+                         *II_wcsdup, *II_win_wcsdup, *II_g_malloc,
+                         *II_g_malloc0, *II_g_realloc, *II_g_try_malloc,
+                         *II_g_try_malloc0, *II_g_try_realloc, *II_g_free,
+                         *II_g_memdup, *II_g_malloc_n, *II_g_malloc0_n,
+                         *II_g_realloc_n, *II_g_try_malloc_n,
+                         *II_g_try_malloc0_n, *II_g_try_realloc_n;
   mutable Optional<uint64_t> KernelZeroFlagVal;
 
   void initIdentifierInfo(ASTContext &C) const;
 
   /// Determine family of a deallocation expression.
   AllocationFamily getAllocationFamily(CheckerContext &C, const Stmt *S) const;
 
   /// Print names of allocators and deallocators.
void MallocChecker::initIdentifierInfo(ASTContext &Ctx) const {
   II_realloc = &Ctx.Idents.get("realloc");
   II_reallocf = &Ctx.Idents.get("reallocf");
   II_calloc = &Ctx.Idents.get("calloc");
   II_valloc = &Ctx.Idents.get("valloc");
   II_strdup = &Ctx.Idents.get("strdup");
   II_strndup = &Ctx.Idents.get("strndup");
   II_wcsdup = &Ctx.Idents.get("wcsdup");
   II_kmalloc = &Ctx.Idents.get("kmalloc");
+  II_kfree = &Ctx.Idents.get("kfree");
   II_if_nameindex = &Ctx.Idents.get("if_nameindex");
   II_if_freenameindex = &Ctx.Idents.get("if_freenameindex");
 
   //MSVC uses `_`-prefixed instead, so we check for them too.
   II_win_strdup = &Ctx.Idents.get("_strdup");
   II_win_wcsdup = &Ctx.Idents.get("_wcsdup");
   II_win_alloca = &Ctx.Idents.get("_alloca");
 
bool CheckAlloc = (MemKind == MemoryOperationKind::MOK_Any ||
                      MemKind == MemoryOperationKind::MOK_Allocate);
 
   if (FD->getKind() == Decl::Function) {
     const IdentifierInfo *FunI = FD->getIdentifier();
     initIdentifierInfo(C);
 
     if (Family == AF_Malloc && CheckFree) {
       if (FunI == II_free || FunI == II_realloc || FunI == II_reallocf ||
-          FunI == II_g_free)
+          FunI == II_g_free || FunI == II_kfree)
         return true;
     }
 
     if (Family == AF_Malloc && CheckAlloc) {
       if (FunI == II_malloc || FunI == II_realloc || FunI == II_reallocf ||
           FunI == II_calloc || FunI == II_valloc || FunI == II_strdup ||
           FunI == II_win_strdup || FunI == II_strndup || FunI == II_wcsdup ||
           FunI == II_win_wcsdup || FunI == II_kmalloc ||
if (FunI == II_malloc || FunI == II_g_malloc || FunI == II_g_try_malloc) {
       State = ProcessZeroAllocation(C, CE, 1, State);
     } else if (FunI == II_reallocf) {
       State = ReallocMemAux(C, CE, true, State);
       State = ProcessZeroAllocation(C, CE, 1, State);
     } else if (FunI == II_calloc) {
       State = CallocMem(C, CE, State);
       State = ProcessZeroAllocation(C, CE, 0, State);
       State = ProcessZeroAllocation(C, CE, 1, State);
-    } else if (FunI == II_free || FunI == II_g_free) {
+    } else if (FunI == II_free || FunI == II_g_free || FunI == II_kfree) {
       State = FreeMemAux(C, CE, State, 0, false, ReleasedAllocatedMemory);
     } else if (FunI == II_strdup || FunI == II_win_strdup ||
                FunI == II_wcsdup || FunI == II_win_wcsdup) {
       State = MallocUpdateRefState(C, CE, State);
     } else if (FunI == II_strndup) {
       State = MallocUpdateRefState(C, CE, State);
     } else if (FunI == II_alloca || FunI == II_win_alloca) {
       if (CE->getNumArgs() < 1)

clang/test/Analysis/kmalloc-linux.c

void test_zeroed() {
   list = kmalloc(sizeof(*list) * 10, __GFP_ZERO);
   if (list == NULL)
     return;
 
   for (i = 0; i < 10; i++) {
     t = list[i];
     foo(t);
   }
-  free(list); // no-warning
+  kfree(list); // no-warning
 }
 
 void test_nonzero() {
   struct test **list, *t;
   int i;
 
   list = kmalloc(sizeof(*list) * 10, 0);
   if (list == NULL)
     return;
 
   for (i = 0; i < 10; i++) {
     t = list[i]; // expected-warning{{undefined}}
     foo(t);
   }
-  free(list);
+  kfree(list);
 }
 
 void test_indeterminate(int flags) {
   struct test **list, *t;
   int i;
 
   list = kmalloc(sizeof(*list) * 10, flags);
   if (list == NULL)
     return;
 
   for (i = 0; i < 10; i++) {
     t = list[i]; // expected-warning{{undefined}}
     foo(t);
   }
-  free(list);
+  kfree(list);
 }