[v2] kasan: fix KASAN unit tests for tag-based KASAN
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Message ID 20200706022150.20848-1-walter-zh.wu@mediatek.com
State New
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  • [v2] kasan: fix KASAN unit tests for tag-based KASAN
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Commit Message

Walter Wu July 6, 2020, 2:21 a.m. UTC
We use tag-based KASAN, then KASAN unit tests don't detect out-of-bounds
memory access. They need to be fixed.

With tag-based KASAN, the state of each 16 aligned bytes of memory is
encoded in one shadow byte and the shadow value is tag of pointer, so
we need to read next shadow byte, the shadow value is not equal to tag
value of pointer, so that tag-based KASAN will detect out-of-bounds
memory access.

Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---

changes since v1:
- Reduce amount of non-compiled code.
- KUnit-KASAN Integration patchset are not merged yet. My patch should
  have conflict with it, if needed, we can continue to wait it.

---

 lib/test_kasan.c | 81 ++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 64 insertions(+), 17 deletions(-)

Comments

Dmitry Vyukov July 6, 2020, 6:19 a.m. UTC | #1
On Mon, Jul 6, 2020 at 4:21 AM Walter Wu <walter-zh.wu@mediatek.com> wrote:
>
> We use tag-based KASAN, then KASAN unit tests don't detect out-of-bounds
> memory access. They need to be fixed.
>
> With tag-based KASAN, the state of each 16 aligned bytes of memory is
> encoded in one shadow byte and the shadow value is tag of pointer, so
> we need to read next shadow byte, the shadow value is not equal to tag
> value of pointer, so that tag-based KASAN will detect out-of-bounds
> memory access.
>
> Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Matthias Brugger <matthias.bgg@gmail.com>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> changes since v1:
> - Reduce amount of non-compiled code.
> - KUnit-KASAN Integration patchset are not merged yet. My patch should
>   have conflict with it, if needed, we can continue to wait it.
>
> ---
>
>  lib/test_kasan.c | 81 ++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 64 insertions(+), 17 deletions(-)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index e3087d90e00d..660664439d52 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -40,7 +40,11 @@ static noinline void __init kmalloc_oob_right(void)
>                 return;
>         }
>
> -       ptr[size] = 'x';
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               ptr[size] = 'x';
> +       else
> +               ptr[size + 5] = 'x';
> +

Hi Walter,

Would if be possible to introduce something like:

#define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : 8)

and then add it throughout as

        ptr[size + OOB_TAG_OFF] = 'x';

?
The current version results in quite some amount of additional code
that needs to be read, extended  and maintained in the future. So I am
thinking if it's possible to minimize it somehow...

>         kfree(ptr);
>  }
>
> @@ -92,7 +96,11 @@ static noinline void __init kmalloc_pagealloc_oob_right(void)
>                 return;
>         }
>
> -       ptr[size] = 0;
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               ptr[size] = 0;
> +       else
> +               ptr[size + 6] = 0;
> +
>         kfree(ptr);
>  }
>
> @@ -162,7 +170,11 @@ static noinline void __init kmalloc_oob_krealloc_more(void)
>                 return;
>         }
>
> -       ptr2[size2] = 'x';
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               ptr2[size2] = 'x';
> +       else
> +               ptr2[size2 + 13] = 'x';
> +
>         kfree(ptr2);
>  }
>
> @@ -180,7 +192,12 @@ static noinline void __init kmalloc_oob_krealloc_less(void)
>                 kfree(ptr1);
>                 return;
>         }
> -       ptr2[size2] = 'x';
> +
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               ptr2[size2] = 'x';
> +       else
> +               ptr2[size2 + 2] = 'x';
> +
>         kfree(ptr2);
>  }
>
> @@ -216,7 +233,11 @@ static noinline void __init kmalloc_oob_memset_2(void)
>                 return;
>         }
>
> -       memset(ptr+7, 0, 2);
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               memset(ptr+7, 0, 2);
> +       else
> +               memset(ptr+15, 0, 2);
> +
>         kfree(ptr);
>  }
>
> @@ -232,7 +253,11 @@ static noinline void __init kmalloc_oob_memset_4(void)
>                 return;
>         }
>
> -       memset(ptr+5, 0, 4);
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               memset(ptr+5, 0, 4);
> +       else
> +               memset(ptr+15, 0, 4);
> +
>         kfree(ptr);
>  }
>
> @@ -249,7 +274,11 @@ static noinline void __init kmalloc_oob_memset_8(void)
>                 return;
>         }
>
> -       memset(ptr+1, 0, 8);
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               memset(ptr+1, 0, 8);
> +       else
> +               memset(ptr+15, 0, 8);
> +
>         kfree(ptr);
>  }
>
> @@ -265,7 +294,11 @@ static noinline void __init kmalloc_oob_memset_16(void)
>                 return;
>         }
>
> -       memset(ptr+1, 0, 16);
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               memset(ptr+1, 0, 16);
> +       else
> +               memset(ptr+15, 0, 16);
> +
>         kfree(ptr);
>  }
>
> @@ -281,7 +314,11 @@ static noinline void __init kmalloc_oob_in_memset(void)
>                 return;
>         }
>
> -       memset(ptr, 0, size+5);
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               memset(ptr, 0, size+5);
> +       else
> +               memset(ptr, 0, size+7);
> +
>         kfree(ptr);
>  }
>
> @@ -415,7 +452,11 @@ static noinline void __init kmem_cache_oob(void)
>                 return;
>         }
>
> -       *p = p[size];
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               *p = p[size];
> +       else
> +               *p = p[size + 8];
> +
>         kmem_cache_free(cache, p);
>         kmem_cache_destroy(cache);
>  }
> @@ -497,6 +538,7 @@ static noinline void __init copy_user_test(void)
>         char __user *usermem;
>         size_t size = 10;
>         int unused;
> +       size_t oob_size;
>
>         kmem = kmalloc(size, GFP_KERNEL);
>         if (!kmem)
> @@ -511,26 +553,31 @@ static noinline void __init copy_user_test(void)
>                 return;
>         }
>
> +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> +               oob_size = 1;
> +       else
> +               oob_size = 7;
> +
>         pr_info("out-of-bounds in copy_from_user()\n");
> -       unused = copy_from_user(kmem, usermem, size + 1);
> +       unused = copy_from_user(kmem, usermem, size + oob_size);
>
>         pr_info("out-of-bounds in copy_to_user()\n");
> -       unused = copy_to_user(usermem, kmem, size + 1);
> +       unused = copy_to_user(usermem, kmem, size + oob_size);
>
>         pr_info("out-of-bounds in __copy_from_user()\n");
> -       unused = __copy_from_user(kmem, usermem, size + 1);
> +       unused = __copy_from_user(kmem, usermem, size + oob_size);
>
>         pr_info("out-of-bounds in __copy_to_user()\n");
> -       unused = __copy_to_user(usermem, kmem, size + 1);
> +       unused = __copy_to_user(usermem, kmem, size + oob_size);
>
>         pr_info("out-of-bounds in __copy_from_user_inatomic()\n");
> -       unused = __copy_from_user_inatomic(kmem, usermem, size + 1);
> +       unused = __copy_from_user_inatomic(kmem, usermem, size + oob_size);
>
>         pr_info("out-of-bounds in __copy_to_user_inatomic()\n");
> -       unused = __copy_to_user_inatomic(usermem, kmem, size + 1);
> +       unused = __copy_to_user_inatomic(usermem, kmem, size + oob_size);
>
>         pr_info("out-of-bounds in strncpy_from_user()\n");
> -       unused = strncpy_from_user(kmem, usermem, size + 1);
> +       unused = strncpy_from_user(kmem, usermem, size + oob_size);
>
>         vm_munmap((unsigned long)usermem, PAGE_SIZE);
>         kfree(kmem);
> --
> 2.18.0
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20200706022150.20848-1-walter-zh.wu%40mediatek.com.
Walter Wu July 6, 2020, 6:59 a.m. UTC | #2
On Mon, 2020-07-06 at 08:19 +0200, Dmitry Vyukov wrote:
> On Mon, Jul 6, 2020 at 4:21 AM Walter Wu <walter-zh.wu@mediatek.com> wrote:
> >
> > We use tag-based KASAN, then KASAN unit tests don't detect out-of-bounds
> > memory access. They need to be fixed.
> >
> > With tag-based KASAN, the state of each 16 aligned bytes of memory is
> > encoded in one shadow byte and the shadow value is tag of pointer, so
> > we need to read next shadow byte, the shadow value is not equal to tag
> > value of pointer, so that tag-based KASAN will detect out-of-bounds
> > memory access.
> >
> > Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
> > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Alexander Potapenko <glider@google.com>
> > Cc: Matthias Brugger <matthias.bgg@gmail.com>
> > Cc: Andrey Konovalov <andreyknvl@google.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > ---
> >
> > changes since v1:
> > - Reduce amount of non-compiled code.
> > - KUnit-KASAN Integration patchset are not merged yet. My patch should
> >   have conflict with it, if needed, we can continue to wait it.
> >
> > ---
> >
> >  lib/test_kasan.c | 81 ++++++++++++++++++++++++++++++++++++++----------
> >  1 file changed, 64 insertions(+), 17 deletions(-)
> >
> > diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> > index e3087d90e00d..660664439d52 100644
> > --- a/lib/test_kasan.c
> > +++ b/lib/test_kasan.c
> > @@ -40,7 +40,11 @@ static noinline void __init kmalloc_oob_right(void)
> >                 return;
> >         }
> >
> > -       ptr[size] = 'x';
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               ptr[size] = 'x';
> > +       else
> > +               ptr[size + 5] = 'x';
> > +
> 
> Hi Walter,
> 
> Would if be possible to introduce something like:
> 
> #define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : 8)
> 

It is good suggestion. Thanks.

> and then add it throughout as
> 
>         ptr[size + OOB_TAG_OFF] = 'x';
> 
> ?
> The current version results in quite some amount of additional code
> that needs to be read, extended  and maintained in the future. So I am
> thinking if it's possible to minimize it somehow...
> 

Ok, I will send next patch by your suggestion.

Thanks.

> >         kfree(ptr);
> >  }
> >
> > @@ -92,7 +96,11 @@ static noinline void __init kmalloc_pagealloc_oob_right(void)
> >                 return;
> >         }
> >
> > -       ptr[size] = 0;
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               ptr[size] = 0;
> > +       else
> > +               ptr[size + 6] = 0;
> > +
> >         kfree(ptr);
> >  }
> >
> > @@ -162,7 +170,11 @@ static noinline void __init kmalloc_oob_krealloc_more(void)
> >                 return;
> >         }
> >
> > -       ptr2[size2] = 'x';
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               ptr2[size2] = 'x';
> > +       else
> > +               ptr2[size2 + 13] = 'x';
> > +
> >         kfree(ptr2);
> >  }
> >
> > @@ -180,7 +192,12 @@ static noinline void __init kmalloc_oob_krealloc_less(void)
> >                 kfree(ptr1);
> >                 return;
> >         }
> > -       ptr2[size2] = 'x';
> > +
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               ptr2[size2] = 'x';
> > +       else
> > +               ptr2[size2 + 2] = 'x';
> > +
> >         kfree(ptr2);
> >  }
> >
> > @@ -216,7 +233,11 @@ static noinline void __init kmalloc_oob_memset_2(void)
> >                 return;
> >         }
> >
> > -       memset(ptr+7, 0, 2);
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               memset(ptr+7, 0, 2);
> > +       else
> > +               memset(ptr+15, 0, 2);
> > +
> >         kfree(ptr);
> >  }
> >
> > @@ -232,7 +253,11 @@ static noinline void __init kmalloc_oob_memset_4(void)
> >                 return;
> >         }
> >
> > -       memset(ptr+5, 0, 4);
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               memset(ptr+5, 0, 4);
> > +       else
> > +               memset(ptr+15, 0, 4);
> > +
> >         kfree(ptr);
> >  }
> >
> > @@ -249,7 +274,11 @@ static noinline void __init kmalloc_oob_memset_8(void)
> >                 return;
> >         }
> >
> > -       memset(ptr+1, 0, 8);
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               memset(ptr+1, 0, 8);
> > +       else
> > +               memset(ptr+15, 0, 8);
> > +
> >         kfree(ptr);
> >  }
> >
> > @@ -265,7 +294,11 @@ static noinline void __init kmalloc_oob_memset_16(void)
> >                 return;
> >         }
> >
> > -       memset(ptr+1, 0, 16);
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               memset(ptr+1, 0, 16);
> > +       else
> > +               memset(ptr+15, 0, 16);
> > +
> >         kfree(ptr);
> >  }
> >
> > @@ -281,7 +314,11 @@ static noinline void __init kmalloc_oob_in_memset(void)
> >                 return;
> >         }
> >
> > -       memset(ptr, 0, size+5);
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               memset(ptr, 0, size+5);
> > +       else
> > +               memset(ptr, 0, size+7);
> > +
> >         kfree(ptr);
> >  }
> >
> > @@ -415,7 +452,11 @@ static noinline void __init kmem_cache_oob(void)
> >                 return;
> >         }
> >
> > -       *p = p[size];
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               *p = p[size];
> > +       else
> > +               *p = p[size + 8];
> > +
> >         kmem_cache_free(cache, p);
> >         kmem_cache_destroy(cache);
> >  }
> > @@ -497,6 +538,7 @@ static noinline void __init copy_user_test(void)
> >         char __user *usermem;
> >         size_t size = 10;
> >         int unused;
> > +       size_t oob_size;
> >
> >         kmem = kmalloc(size, GFP_KERNEL);
> >         if (!kmem)
> > @@ -511,26 +553,31 @@ static noinline void __init copy_user_test(void)
> >                 return;
> >         }
> >
> > +       if (IS_ENABLED(CONFIG_KASAN_GENERIC))
> > +               oob_size = 1;
> > +       else
> > +               oob_size = 7;
> > +
> >         pr_info("out-of-bounds in copy_from_user()\n");
> > -       unused = copy_from_user(kmem, usermem, size + 1);
> > +       unused = copy_from_user(kmem, usermem, size + oob_size);
> >
> >         pr_info("out-of-bounds in copy_to_user()\n");
> > -       unused = copy_to_user(usermem, kmem, size + 1);
> > +       unused = copy_to_user(usermem, kmem, size + oob_size);
> >
> >         pr_info("out-of-bounds in __copy_from_user()\n");
> > -       unused = __copy_from_user(kmem, usermem, size + 1);
> > +       unused = __copy_from_user(kmem, usermem, size + oob_size);
> >
> >         pr_info("out-of-bounds in __copy_to_user()\n");
> > -       unused = __copy_to_user(usermem, kmem, size + 1);
> > +       unused = __copy_to_user(usermem, kmem, size + oob_size);
> >
> >         pr_info("out-of-bounds in __copy_from_user_inatomic()\n");
> > -       unused = __copy_from_user_inatomic(kmem, usermem, size + 1);
> > +       unused = __copy_from_user_inatomic(kmem, usermem, size + oob_size);
> >
> >         pr_info("out-of-bounds in __copy_to_user_inatomic()\n");
> > -       unused = __copy_to_user_inatomic(usermem, kmem, size + 1);
> > +       unused = __copy_to_user_inatomic(usermem, kmem, size + oob_size);
> >
> >         pr_info("out-of-bounds in strncpy_from_user()\n");
> > -       unused = strncpy_from_user(kmem, usermem, size + 1);
> > +       unused = strncpy_from_user(kmem, usermem, size + oob_size);
> >
> >         vm_munmap((unsigned long)usermem, PAGE_SIZE);
> >         kfree(kmem);
> > --
> > 2.18.0
> >
> > --
> > You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
> > To view this discussion on the web visit https://urldefense.com/v3/__https://groups.google.com/d/msgid/kasan-dev/20200706022150.20848-1-walter-zh.wu*40mediatek.com__;JQ!!CTRNKA9wMg0ARbw!zqGS_g-oLI7o6850GjV_P7YQPr8SufdeC8fbnt27o4WtvhX5PZ8-eZ6BWyF3bwm7Tizipw$ .

Patch
diff mbox series

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index e3087d90e00d..660664439d52 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -40,7 +40,11 @@  static noinline void __init kmalloc_oob_right(void)
 		return;
 	}
 
-	ptr[size] = 'x';
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		ptr[size] = 'x';
+	else
+		ptr[size + 5] = 'x';
+
 	kfree(ptr);
 }
 
@@ -92,7 +96,11 @@  static noinline void __init kmalloc_pagealloc_oob_right(void)
 		return;
 	}
 
-	ptr[size] = 0;
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		ptr[size] = 0;
+	else
+		ptr[size + 6] = 0;
+
 	kfree(ptr);
 }
 
@@ -162,7 +170,11 @@  static noinline void __init kmalloc_oob_krealloc_more(void)
 		return;
 	}
 
-	ptr2[size2] = 'x';
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		ptr2[size2] = 'x';
+	else
+		ptr2[size2 + 13] = 'x';
+
 	kfree(ptr2);
 }
 
@@ -180,7 +192,12 @@  static noinline void __init kmalloc_oob_krealloc_less(void)
 		kfree(ptr1);
 		return;
 	}
-	ptr2[size2] = 'x';
+
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		ptr2[size2] = 'x';
+	else
+		ptr2[size2 + 2] = 'x';
+
 	kfree(ptr2);
 }
 
@@ -216,7 +233,11 @@  static noinline void __init kmalloc_oob_memset_2(void)
 		return;
 	}
 
-	memset(ptr+7, 0, 2);
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		memset(ptr+7, 0, 2);
+	else
+		memset(ptr+15, 0, 2);
+
 	kfree(ptr);
 }
 
@@ -232,7 +253,11 @@  static noinline void __init kmalloc_oob_memset_4(void)
 		return;
 	}
 
-	memset(ptr+5, 0, 4);
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		memset(ptr+5, 0, 4);
+	else
+		memset(ptr+15, 0, 4);
+
 	kfree(ptr);
 }
 
@@ -249,7 +274,11 @@  static noinline void __init kmalloc_oob_memset_8(void)
 		return;
 	}
 
-	memset(ptr+1, 0, 8);
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		memset(ptr+1, 0, 8);
+	else
+		memset(ptr+15, 0, 8);
+
 	kfree(ptr);
 }
 
@@ -265,7 +294,11 @@  static noinline void __init kmalloc_oob_memset_16(void)
 		return;
 	}
 
-	memset(ptr+1, 0, 16);
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		memset(ptr+1, 0, 16);
+	else
+		memset(ptr+15, 0, 16);
+
 	kfree(ptr);
 }
 
@@ -281,7 +314,11 @@  static noinline void __init kmalloc_oob_in_memset(void)
 		return;
 	}
 
-	memset(ptr, 0, size+5);
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		memset(ptr, 0, size+5);
+	else
+		memset(ptr, 0, size+7);
+
 	kfree(ptr);
 }
 
@@ -415,7 +452,11 @@  static noinline void __init kmem_cache_oob(void)
 		return;
 	}
 
-	*p = p[size];
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		*p = p[size];
+	else
+		*p = p[size + 8];
+
 	kmem_cache_free(cache, p);
 	kmem_cache_destroy(cache);
 }
@@ -497,6 +538,7 @@  static noinline void __init copy_user_test(void)
 	char __user *usermem;
 	size_t size = 10;
 	int unused;
+	size_t oob_size;
 
 	kmem = kmalloc(size, GFP_KERNEL);
 	if (!kmem)
@@ -511,26 +553,31 @@  static noinline void __init copy_user_test(void)
 		return;
 	}
 
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		oob_size = 1;
+	else
+		oob_size = 7;
+
 	pr_info("out-of-bounds in copy_from_user()\n");
-	unused = copy_from_user(kmem, usermem, size + 1);
+	unused = copy_from_user(kmem, usermem, size + oob_size);
 
 	pr_info("out-of-bounds in copy_to_user()\n");
-	unused = copy_to_user(usermem, kmem, size + 1);
+	unused = copy_to_user(usermem, kmem, size + oob_size);
 
 	pr_info("out-of-bounds in __copy_from_user()\n");
-	unused = __copy_from_user(kmem, usermem, size + 1);
+	unused = __copy_from_user(kmem, usermem, size + oob_size);
 
 	pr_info("out-of-bounds in __copy_to_user()\n");
-	unused = __copy_to_user(usermem, kmem, size + 1);
+	unused = __copy_to_user(usermem, kmem, size + oob_size);
 
 	pr_info("out-of-bounds in __copy_from_user_inatomic()\n");
-	unused = __copy_from_user_inatomic(kmem, usermem, size + 1);
+	unused = __copy_from_user_inatomic(kmem, usermem, size + oob_size);
 
 	pr_info("out-of-bounds in __copy_to_user_inatomic()\n");
-	unused = __copy_to_user_inatomic(usermem, kmem, size + 1);
+	unused = __copy_to_user_inatomic(usermem, kmem, size + oob_size);
 
 	pr_info("out-of-bounds in strncpy_from_user()\n");
-	unused = strncpy_from_user(kmem, usermem, size + 1);
+	unused = strncpy_from_user(kmem, usermem, size + oob_size);
 
 	vm_munmap((unsigned long)usermem, PAGE_SIZE);
 	kfree(kmem);