Handle NULL input to malloc_usable_size [BZ #28506]

Hoist the NULL check for malloc_usable_size into its entry points in
malloc-debug and malloc and assume non-NULL in all callees.  This fixes
BZ #28506

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>

3 files changed, 25 insertions, 35 deletions

diff --git a/malloc/malloc-debug.c b/malloc/malloc-debug.c
index 9922ef5..3d7e6d4 100644
--- a/malloc/malloc-debug.c
+++ b/malloc/malloc-debug.c
@@ -1,5 +1,6 @@
 /* Malloc debug DSO.
    Copyright (C) 2021 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -399,17 +400,17 @@ strong_alias (__debug_calloc, calloc)
 size_t
 malloc_usable_size (void *mem)
 {
+  if (mem == NULL)
+    return 0;
+
   if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
     return mcheck_usable_size (mem);
   if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
     return malloc_check_get_size (mem);
 
-  if (mem != NULL)
-    {
-      mchunkptr p = mem2chunk (mem);
-     if (DUMPED_MAIN_ARENA_CHUNK (p))
-       return chunksize (p) - SIZE_SZ;
-    }
+  mchunkptr p = mem2chunk (mem);
+  if (DUMPED_MAIN_ARENA_CHUNK (p))
+    return chunksize (p) - SIZE_SZ;
 
   return musable (mem);
 }
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 2ba1fee..095d97a 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1,5 +1,6 @@
 /* Malloc implementation for multiple threads without lock contention.
    Copyright (C) 1996-2021 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -5007,20 +5008,13 @@ __malloc_trim (size_t s)
 static size_t
 musable (void *mem)
 {
-  mchunkptr p;
-  if (mem != 0)
-    {
-      size_t result = 0;
-
-      p = mem2chunk (mem);
+  mchunkptr p = mem2chunk (mem);
 
-      if (chunk_is_mmapped (p))
-	result = chunksize (p) - CHUNK_HDR_SZ;
-      else if (inuse (p))
-	result = memsize (p);
+  if (chunk_is_mmapped (p))
+    return chunksize (p) - CHUNK_HDR_SZ;
+  else if (inuse (p))
+    return memsize (p);
 
-      return result;
-    }
   return 0;
 }
 
@@ -5028,10 +5022,9 @@ musable (void *mem)
 size_t
 __malloc_usable_size (void *m)
 {
-  size_t result;
-
-  result = musable (m);
-  return result;
+  if (m == NULL)
+    return 0;
+  return musable (m);
 }
 #endif
 
diff --git a/malloc/tst-malloc-usable.c b/malloc/tst-malloc-usable.c
index a1074b7..b0d702b 100644
--- a/malloc/tst-malloc-usable.c
+++ b/malloc/tst-malloc-usable.c
@@ -2,6 +2,7 @@
    MALLOC_CHECK_ exported to a positive value.
 
    Copyright (C) 2012-2021 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -21,29 +22,24 @@
 #include <malloc.h>
 #include <string.h>
 #include <stdio.h>
+#include <support/support.h>
+#include <support/check.h>
 
 static int
 do_test (void)
 {
   size_t usable_size;
   void *p = malloc (7);
-  if (!p)
-    {
-      printf ("memory allocation failed\n");
-      return 1;
-    }
 
+  TEST_VERIFY_EXIT (p != NULL);
   usable_size = malloc_usable_size (p);
-  if (usable_size != 7)
-    {
-      printf ("malloc_usable_size: expected 7 but got %zu\n", usable_size);
-      return 1;
-    }
-
+  TEST_COMPARE (usable_size, 7);
   memset (p, 0, usable_size);
   free (p);
+
+  TEST_COMPARE (malloc_usable_size (NULL), 0);
+
   return 0;
 }
 
-#define TEST_FUNCTION do_test ()
-#include "../test-skeleton.c"
+#include "support/test-driver.c"