diff mbox series

Handle NULL input to malloc_usable_size [BZ #28506]

Message ID 20211029031802.254600-1-siddhesh@sourceware.org
State Superseded
Headers
Series Handle NULL input to malloc_usable_size [BZ #28506] |

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent
dj/TryBot-32bit success Build for i686

Commit Message

Siddhesh Poyarekar Oct. 29, 2021, 3:18 a.m. UTC 
  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>
---
 malloc/malloc-debug.c      | 12 ++++++------
 malloc/malloc.c            | 23 ++++++++++-------------
 malloc/tst-malloc-usable.c | 21 ++++++++-------------
 3 files changed, 24 insertions(+), 32 deletions(-)

Comments

Florian Weimer Oct. 29, 2021, 8:30 a.m. UTC | #1 
* Siddhesh Poyarekar via Libc-alpha:

>  size_t
>  __malloc_usable_size (void *m)
>  {
> +  size_t result = 0;
>  
> +  if (m != NULL)
> +    result = musable (m);
>    return result;
>  }

Is there a reason for not writing it this way?

size_t
__malloc_usable_size (void *m)
{
  if (m == NULL)
    return 0;
  return musable (m);
}

The extra variable seems a bit … unnecessary?

> diff --git a/malloc/tst-malloc-usable.c b/malloc/tst-malloc-usable.c
> index a1074b782a..cd5c27cfcd 100644
> --- a/malloc/tst-malloc-usable.c
> +++ b/malloc/tst-malloc-usable.c
> @@ -21,29 +21,24 @@
>  #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);
>  
> +  TEST_VERIFY_EXIT (p != NULL);
>    usable_size = malloc_usable_size (p);
> +  TEST_VERIFY_EXIT (usable_size == 7);

You can use TEST_COMPARE here.

>    memset (p, 0, usable_size);
>    free (p);
> +
> +  TEST_VERIFY_EXIT (malloc_usable_size (NULL) == 0);

And here.

Thanks,
Florian
diff mbox series

Patch

diff --git a/malloc/malloc-debug.c b/malloc/malloc-debug.c
index 9922ef5f25..5e954d7dc2 100644
--- a/malloc/malloc-debug.c
+++ b/malloc/malloc-debug.c
@@ -399,17 +399,17 @@  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 2ba1fee144..9a345572a1 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -5008,29 +5008,26 @@  static size_t
 musable (void *mem)
 {
   mchunkptr p;
-  if (mem != 0)
-    {
-      size_t result = 0;
+  size_t result = 0;
 
-      p = mem2chunk (mem);
+  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))
+    result = chunksize (p) - CHUNK_HDR_SZ;
+  else if (inuse (p))
+    result = memsize (p);
 
-      return result;
-    }
-  return 0;
+  return result;
 }
 
 #if IS_IN (libc)
 size_t
 __malloc_usable_size (void *m)
 {
-  size_t result;
+  size_t result = 0;
 
-  result = musable (m);
+  if (m != NULL)
+    result = musable (m);
   return result;
 }
 #endif
diff --git a/malloc/tst-malloc-usable.c b/malloc/tst-malloc-usable.c
index a1074b782a..cd5c27cfcd 100644
--- a/malloc/tst-malloc-usable.c
+++ b/malloc/tst-malloc-usable.c
@@ -21,29 +21,24 @@ 
 #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_VERIFY_EXIT (usable_size == 7);
   memset (p, 0, usable_size);
   free (p);
+
+  TEST_VERIFY_EXIT (malloc_usable_size (NULL) == 0);
+
   return 0;
 }
 
-#define TEST_FUNCTION do_test ()
-#include "../test-skeleton.c"
+#include "support/test-driver.c"