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[v1,1/3] String: Add additional overflow tests for strnlen, memchr, and strncat

Message ID 20210609205257.123944-1-goldstein.w.n@gmail.com
State New
Headers show
Series [v1,1/3] String: Add additional overflow tests for strnlen, memchr, and strncat | expand

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Commit Message

Noah Goldstein June 9, 2021, 8:52 p.m. UTC
This commit adds tests for a bug in the wide char variant of the
functions where the implementation may assume that maxlen for wcsnlen
or n for wmemchr/strncat will not overflow when multiplied by
sizeof(wchar_t).

These tests show the following implementations failing on x86_64:

wcsnlen-sse4_1
wcsnlen-avx2

wmemchr-sse2
wmemchr-avx2

strncat would fail as well if it where on a system that prefered
either of the wcsnlen implementations that failed as it relies on
wcsnlen.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
 string/test-memchr.c  | 39 ++++++++++++++++++++++++---
 string/test-strncat.c | 61 +++++++++++++++++++++++++++++++++++++++++++
 string/test-strnlen.c | 33 +++++++++++++++++++++++
 3 files changed, 130 insertions(+), 3 deletions(-)

Comments

H.J. Lu June 9, 2021, 9:53 p.m. UTC | #1
On Wed, Jun 9, 2021 at 1:53 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> This commit adds tests for a bug in the wide char variant of the
> functions where the implementation may assume that maxlen for wcsnlen
> or n for wmemchr/strncat will not overflow when multiplied by
> sizeof(wchar_t).
>
> These tests show the following implementations failing on x86_64:
>
> wcsnlen-sse4_1
> wcsnlen-avx2
>
> wmemchr-sse2
> wmemchr-avx2
>
> strncat would fail as well if it where on a system that prefered
> either of the wcsnlen implementations that failed as it relies on
> wcsnlen.

Please open a bug report for each standard C function.   We need to
track them for backporting to release branches.

Thanks.

> Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> ---
>  string/test-memchr.c  | 39 ++++++++++++++++++++++++---
>  string/test-strncat.c | 61 +++++++++++++++++++++++++++++++++++++++++++
>  string/test-strnlen.c | 33 +++++++++++++++++++++++
>  3 files changed, 130 insertions(+), 3 deletions(-)
>
> diff --git a/string/test-memchr.c b/string/test-memchr.c
> index 665edc32af..ce964284aa 100644
> --- a/string/test-memchr.c
> +++ b/string/test-memchr.c
> @@ -65,8 +65,8 @@ do_one_test (impl_t *impl, const CHAR *s, int c, size_t n, CHAR *exp_res)
>    CHAR *res = CALL (impl, s, c, n);
>    if (res != exp_res)
>      {
> -      error (0, 0, "Wrong result in function %s %p %p", impl->name,
> -            res, exp_res);
> +      error (0, 0, "Wrong result in function %s (%p, %d, %zu) -> %p != %p",
> +             impl->name, s, c, n, res, exp_res);
>        ret = 1;
>        return;
>      }
> @@ -91,7 +91,7 @@ do_test (size_t align, size_t pos, size_t len, size_t n, int seek_char)
>      }
>    buf[align + len] = 0;
>
> -  if (pos < len)
> +  if (pos < MIN(n, len))
>      {
>        buf[align + pos] = seek_char;
>        buf[align + len] = -seek_char;
> @@ -107,6 +107,38 @@ do_test (size_t align, size_t pos, size_t len, size_t n, int seek_char)
>      do_one_test (impl, (CHAR *) (buf + align), seek_char, n, result);
>  }
>
> +static void
> +do_overflow_tests (void)
> +{
> +  size_t i, j, len;
> +  const size_t one = 1;
> +  uintptr_t buf_addr = (uintptr_t) buf1;
> +
> +  for (i = 0; i < 750; ++i)
> +    {
> +        do_test (0, i, 751, SIZE_MAX - i, BIG_CHAR);
> +        do_test (0, i, 751, i - buf_addr, BIG_CHAR);
> +        do_test (0, i, 751, -buf_addr - i, BIG_CHAR);
> +        do_test (0, i, 751, SIZE_MAX - buf_addr - i, BIG_CHAR);
> +        do_test (0, i, 751, SIZE_MAX - buf_addr + i, BIG_CHAR);
> +
> +      len = 0;
> +      for (j = 8 * sizeof(size_t) - 1; j ; --j)
> +        {
> +          len |= one << j;
> +          do_test (0, i, 751, len - i, BIG_CHAR);
> +          do_test (0, i, 751, len + i, BIG_CHAR);
> +          do_test (0, i, 751, len - buf_addr - i, BIG_CHAR);
> +          do_test (0, i, 751, len - buf_addr + i, BIG_CHAR);
> +
> +          do_test (0, i, 751, ~len - i, BIG_CHAR);
> +          do_test (0, i, 751, ~len + i, BIG_CHAR);
> +          do_test (0, i, 751, ~len - buf_addr - i, BIG_CHAR);
> +          do_test (0, i, 751, ~len - buf_addr + i, BIG_CHAR);
> +        }
> +    }
> +}
> +
>  static void
>  do_random_tests (void)
>  {
> @@ -221,6 +253,7 @@ test_main (void)
>      do_test (page_size / 2 - i, i, i, 1, 0x9B);
>
>    do_random_tests ();
> +  do_overflow_tests ();
>    return ret;
>  }
>
> diff --git a/string/test-strncat.c b/string/test-strncat.c
> index 2ef917b820..0ab7541d4e 100644
> --- a/string/test-strncat.c
> +++ b/string/test-strncat.c
> @@ -134,6 +134,66 @@ do_test (size_t align1, size_t align2, size_t len1, size_t len2,
>      }
>  }
>
> +static void
> +do_overflow_tests (void)
> +{
> +  size_t i, j, len;
> +  const size_t one = 1;
> +  CHAR *s1, *s2;
> +  uintptr_t s1_addr;
> +  s1 = (CHAR *) buf1;
> +  s2 = (CHAR *) buf2;
> +  s1_addr = (uintptr_t)s1;
> + for (j = 0; j < 200; ++j)
> +      s2[j] = 32 + 23 * j % (BIG_CHAR - 32);
> + s2[200] = 0;
> +  for (i = 0; i < 750; ++i) {
> +    for (j = 0; j < i; ++j)
> +      s1[j] = 32 + 23 * j % (BIG_CHAR - 32);
> +    s1[i] = '\0';
> +
> +       FOR_EACH_IMPL (impl, 0)
> +    {
> +      s2[0] = '\0';
> +      do_one_test (impl, s2, s1, SIZE_MAX - i);
> +      s2[0] = '\0';
> +      do_one_test (impl, s2, s1, i - s1_addr);
> +      s2[0] = '\0';
> +      do_one_test (impl, s2, s1, -s1_addr - i);
> +      s2[0] = '\0';
> +      do_one_test (impl, s2, s1, SIZE_MAX - s1_addr - i);
> +      s2[0] = '\0';
> +      do_one_test (impl, s2, s1, SIZE_MAX - s1_addr + i);
> +    }
> +
> +    len = 0;
> +    for (j = 8 * sizeof(size_t) - 1; j ; --j)
> +      {
> +        len |= one << j;
> +        FOR_EACH_IMPL (impl, 0)
> +          {
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, len - i);
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, len + i);
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, len - s1_addr - i);
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, len - s1_addr + i);
> +
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, ~len - i);
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, ~len + i);
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, ~len - s1_addr - i);
> +            s2[0] = '\0';
> +            do_one_test (impl, s2, s1, ~len - s1_addr + i);
> +          }
> +      }
> +  }
> +}
> +
>  static void
>  do_random_tests (void)
>  {
> @@ -316,6 +376,7 @@ test_main (void)
>      }
>
>    do_random_tests ();
> +  do_overflow_tests ();
>    return ret;
>  }
>
> diff --git a/string/test-strnlen.c b/string/test-strnlen.c
> index 920f58e97b..f53e09263f 100644
> --- a/string/test-strnlen.c
> +++ b/string/test-strnlen.c
> @@ -89,6 +89,38 @@ do_test (size_t align, size_t len, size_t maxlen, int max_char)
>      do_one_test (impl, (CHAR *) (buf + align), maxlen, MIN (len, maxlen));
>  }
>
> +static void
> +do_overflow_tests (void)
> +{
> +  size_t i, j, len;
> +  const size_t one = 1;
> +  uintptr_t buf_addr = (uintptr_t) buf1;
> +
> +  for (i = 0; i < 750; ++i)
> +    {
> +      do_test (0, i, SIZE_MAX - i, BIG_CHAR);
> +      do_test (0, i, i - buf_addr, BIG_CHAR);
> +      do_test (0, i, -buf_addr - i, BIG_CHAR);
> +      do_test (0, i, SIZE_MAX - buf_addr - i, BIG_CHAR);
> +      do_test (0, i, SIZE_MAX - buf_addr + i, BIG_CHAR);
> +
> +      len = 0;
> +      for (j = 8 * sizeof(size_t) - 1; j ; --j)
> +        {
> +          len |= one << j;
> +          do_test (0, i, len - i, BIG_CHAR);
> +          do_test (0, i, len + i, BIG_CHAR);
> +          do_test (0, i, len - buf_addr - i, BIG_CHAR);
> +          do_test (0, i, len - buf_addr + i, BIG_CHAR);
> +
> +          do_test (0, i, ~len - i, BIG_CHAR);
> +          do_test (0, i, ~len + i, BIG_CHAR);
> +          do_test (0, i, ~len - buf_addr - i, BIG_CHAR);
> +          do_test (0, i, ~len - buf_addr + i, BIG_CHAR);
> +        }
> +    }
> +}
> +
>  static void
>  do_random_tests (void)
>  {
> @@ -283,6 +315,7 @@ test_main (void)
>    do_random_tests ();
>    do_page_tests ();
>    do_page_2_tests ();
> +  do_overflow_tests ();
>    return ret;
>  }
>
> --
> 2.25.1
>
Noah Goldstein June 9, 2021, 10:26 p.m. UTC | #2
On Wed, Jun 9, 2021 at 5:54 PM H.J. Lu <hjl.tools@gmail.com> wrote:

> On Wed, Jun 9, 2021 at 1:53 PM Noah Goldstein <goldstein.w.n@gmail.com>
> wrote:
> >
> > This commit adds tests for a bug in the wide char variant of the
> > functions where the implementation may assume that maxlen for wcsnlen
> > or n for wmemchr/strncat will not overflow when multiplied by
> > sizeof(wchar_t).
> >
> > These tests show the following implementations failing on x86_64:
> >
> > wcsnlen-sse4_1
> > wcsnlen-avx2
> >
> > wmemchr-sse2
> > wmemchr-avx2
> >
> > strncat would fail as well if it where on a system that prefered
> > either of the wcsnlen implementations that failed as it relies on
> > wcsnlen.
>
> Please open a bug report for each standard C function.   We need to
> track them for backporting to release branches.
>

Done: https://sourceware.org/bugzilla/show_bug.cgi?id=27974


>
> Thanks.
>
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> >  string/test-memchr.c  | 39 ++++++++++++++++++++++++---
> >  string/test-strncat.c | 61 +++++++++++++++++++++++++++++++++++++++++++
> >  string/test-strnlen.c | 33 +++++++++++++++++++++++
> >  3 files changed, 130 insertions(+), 3 deletions(-)
> >
> > diff --git a/string/test-memchr.c b/string/test-memchr.c
> > index 665edc32af..ce964284aa 100644
> > --- a/string/test-memchr.c
> > +++ b/string/test-memchr.c
> > @@ -65,8 +65,8 @@ do_one_test (impl_t *impl, const CHAR *s, int c,
> size_t n, CHAR *exp_res)
> >    CHAR *res = CALL (impl, s, c, n);
> >    if (res != exp_res)
> >      {
> > -      error (0, 0, "Wrong result in function %s %p %p", impl->name,
> > -            res, exp_res);
> > +      error (0, 0, "Wrong result in function %s (%p, %d, %zu) -> %p !=
> %p",
> > +             impl->name, s, c, n, res, exp_res);
> >        ret = 1;
> >        return;
> >      }
> > @@ -91,7 +91,7 @@ do_test (size_t align, size_t pos, size_t len, size_t
> n, int seek_char)
> >      }
> >    buf[align + len] = 0;
> >
> > -  if (pos < len)
> > +  if (pos < MIN(n, len))
> >      {
> >        buf[align + pos] = seek_char;
> >        buf[align + len] = -seek_char;
> > @@ -107,6 +107,38 @@ do_test (size_t align, size_t pos, size_t len,
> size_t n, int seek_char)
> >      do_one_test (impl, (CHAR *) (buf + align), seek_char, n, result);
> >  }
> >
> > +static void
> > +do_overflow_tests (void)
> > +{
> > +  size_t i, j, len;
> > +  const size_t one = 1;
> > +  uintptr_t buf_addr = (uintptr_t) buf1;
> > +
> > +  for (i = 0; i < 750; ++i)
> > +    {
> > +        do_test (0, i, 751, SIZE_MAX - i, BIG_CHAR);
> > +        do_test (0, i, 751, i - buf_addr, BIG_CHAR);
> > +        do_test (0, i, 751, -buf_addr - i, BIG_CHAR);
> > +        do_test (0, i, 751, SIZE_MAX - buf_addr - i, BIG_CHAR);
> > +        do_test (0, i, 751, SIZE_MAX - buf_addr + i, BIG_CHAR);
> > +
> > +      len = 0;
> > +      for (j = 8 * sizeof(size_t) - 1; j ; --j)
> > +        {
> > +          len |= one << j;
> > +          do_test (0, i, 751, len - i, BIG_CHAR);
> > +          do_test (0, i, 751, len + i, BIG_CHAR);
> > +          do_test (0, i, 751, len - buf_addr - i, BIG_CHAR);
> > +          do_test (0, i, 751, len - buf_addr + i, BIG_CHAR);
> > +
> > +          do_test (0, i, 751, ~len - i, BIG_CHAR);
> > +          do_test (0, i, 751, ~len + i, BIG_CHAR);
> > +          do_test (0, i, 751, ~len - buf_addr - i, BIG_CHAR);
> > +          do_test (0, i, 751, ~len - buf_addr + i, BIG_CHAR);
> > +        }
> > +    }
> > +}
> > +
> >  static void
> >  do_random_tests (void)
> >  {
> > @@ -221,6 +253,7 @@ test_main (void)
> >      do_test (page_size / 2 - i, i, i, 1, 0x9B);
> >
> >    do_random_tests ();
> > +  do_overflow_tests ();
> >    return ret;
> >  }
> >
> > diff --git a/string/test-strncat.c b/string/test-strncat.c
> > index 2ef917b820..0ab7541d4e 100644
> > --- a/string/test-strncat.c
> > +++ b/string/test-strncat.c
> > @@ -134,6 +134,66 @@ do_test (size_t align1, size_t align2, size_t len1,
> size_t len2,
> >      }
> >  }
> >
> > +static void
> > +do_overflow_tests (void)
> > +{
> > +  size_t i, j, len;
> > +  const size_t one = 1;
> > +  CHAR *s1, *s2;
> > +  uintptr_t s1_addr;
> > +  s1 = (CHAR *) buf1;
> > +  s2 = (CHAR *) buf2;
> > +  s1_addr = (uintptr_t)s1;
> > + for (j = 0; j < 200; ++j)
> > +      s2[j] = 32 + 23 * j % (BIG_CHAR - 32);
> > + s2[200] = 0;
> > +  for (i = 0; i < 750; ++i) {
> > +    for (j = 0; j < i; ++j)
> > +      s1[j] = 32 + 23 * j % (BIG_CHAR - 32);
> > +    s1[i] = '\0';
> > +
> > +       FOR_EACH_IMPL (impl, 0)
> > +    {
> > +      s2[0] = '\0';
> > +      do_one_test (impl, s2, s1, SIZE_MAX - i);
> > +      s2[0] = '\0';
> > +      do_one_test (impl, s2, s1, i - s1_addr);
> > +      s2[0] = '\0';
> > +      do_one_test (impl, s2, s1, -s1_addr - i);
> > +      s2[0] = '\0';
> > +      do_one_test (impl, s2, s1, SIZE_MAX - s1_addr - i);
> > +      s2[0] = '\0';
> > +      do_one_test (impl, s2, s1, SIZE_MAX - s1_addr + i);
> > +    }
> > +
> > +    len = 0;
> > +    for (j = 8 * sizeof(size_t) - 1; j ; --j)
> > +      {
> > +        len |= one << j;
> > +        FOR_EACH_IMPL (impl, 0)
> > +          {
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, len - i);
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, len + i);
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, len - s1_addr - i);
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, len - s1_addr + i);
> > +
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, ~len - i);
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, ~len + i);
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, ~len - s1_addr - i);
> > +            s2[0] = '\0';
> > +            do_one_test (impl, s2, s1, ~len - s1_addr + i);
> > +          }
> > +      }
> > +  }
> > +}
> > +
> >  static void
> >  do_random_tests (void)
> >  {
> > @@ -316,6 +376,7 @@ test_main (void)
> >      }
> >
> >    do_random_tests ();
> > +  do_overflow_tests ();
> >    return ret;
> >  }
> >
> > diff --git a/string/test-strnlen.c b/string/test-strnlen.c
> > index 920f58e97b..f53e09263f 100644
> > --- a/string/test-strnlen.c
> > +++ b/string/test-strnlen.c
> > @@ -89,6 +89,38 @@ do_test (size_t align, size_t len, size_t maxlen, int
> max_char)
> >      do_one_test (impl, (CHAR *) (buf + align), maxlen, MIN (len,
> maxlen));
> >  }
> >
> > +static void
> > +do_overflow_tests (void)
> > +{
> > +  size_t i, j, len;
> > +  const size_t one = 1;
> > +  uintptr_t buf_addr = (uintptr_t) buf1;
> > +
> > +  for (i = 0; i < 750; ++i)
> > +    {
> > +      do_test (0, i, SIZE_MAX - i, BIG_CHAR);
> > +      do_test (0, i, i - buf_addr, BIG_CHAR);
> > +      do_test (0, i, -buf_addr - i, BIG_CHAR);
> > +      do_test (0, i, SIZE_MAX - buf_addr - i, BIG_CHAR);
> > +      do_test (0, i, SIZE_MAX - buf_addr + i, BIG_CHAR);
> > +
> > +      len = 0;
> > +      for (j = 8 * sizeof(size_t) - 1; j ; --j)
> > +        {
> > +          len |= one << j;
> > +          do_test (0, i, len - i, BIG_CHAR);
> > +          do_test (0, i, len + i, BIG_CHAR);
> > +          do_test (0, i, len - buf_addr - i, BIG_CHAR);
> > +          do_test (0, i, len - buf_addr + i, BIG_CHAR);
> > +
> > +          do_test (0, i, ~len - i, BIG_CHAR);
> > +          do_test (0, i, ~len + i, BIG_CHAR);
> > +          do_test (0, i, ~len - buf_addr - i, BIG_CHAR);
> > +          do_test (0, i, ~len - buf_addr + i, BIG_CHAR);
> > +        }
> > +    }
> > +}
> > +
> >  static void
> >  do_random_tests (void)
> >  {
> > @@ -283,6 +315,7 @@ test_main (void)
> >    do_random_tests ();
> >    do_page_tests ();
> >    do_page_2_tests ();
> > +  do_overflow_tests ();
> >    return ret;
> >  }
> >
> > --
> > 2.25.1
> >
>
>
> --
> H.J.
>
diff mbox series

Patch

diff --git a/string/test-memchr.c b/string/test-memchr.c
index 665edc32af..ce964284aa 100644
--- a/string/test-memchr.c
+++ b/string/test-memchr.c
@@ -65,8 +65,8 @@  do_one_test (impl_t *impl, const CHAR *s, int c, size_t n, CHAR *exp_res)
   CHAR *res = CALL (impl, s, c, n);
   if (res != exp_res)
     {
-      error (0, 0, "Wrong result in function %s %p %p", impl->name,
-	     res, exp_res);
+      error (0, 0, "Wrong result in function %s (%p, %d, %zu) -> %p != %p",
+             impl->name, s, c, n, res, exp_res);
       ret = 1;
       return;
     }
@@ -91,7 +91,7 @@  do_test (size_t align, size_t pos, size_t len, size_t n, int seek_char)
     }
   buf[align + len] = 0;
 
-  if (pos < len)
+  if (pos < MIN(n, len))
     {
       buf[align + pos] = seek_char;
       buf[align + len] = -seek_char;
@@ -107,6 +107,38 @@  do_test (size_t align, size_t pos, size_t len, size_t n, int seek_char)
     do_one_test (impl, (CHAR *) (buf + align), seek_char, n, result);
 }
 
+static void
+do_overflow_tests (void)
+{
+  size_t i, j, len;
+  const size_t one = 1;
+  uintptr_t buf_addr = (uintptr_t) buf1;
+
+  for (i = 0; i < 750; ++i)
+    {
+        do_test (0, i, 751, SIZE_MAX - i, BIG_CHAR);
+        do_test (0, i, 751, i - buf_addr, BIG_CHAR);
+        do_test (0, i, 751, -buf_addr - i, BIG_CHAR);
+        do_test (0, i, 751, SIZE_MAX - buf_addr - i, BIG_CHAR);
+        do_test (0, i, 751, SIZE_MAX - buf_addr + i, BIG_CHAR);
+
+      len = 0;
+      for (j = 8 * sizeof(size_t) - 1; j ; --j)
+        {
+          len |= one << j;
+          do_test (0, i, 751, len - i, BIG_CHAR);
+          do_test (0, i, 751, len + i, BIG_CHAR);
+          do_test (0, i, 751, len - buf_addr - i, BIG_CHAR);
+          do_test (0, i, 751, len - buf_addr + i, BIG_CHAR);
+
+          do_test (0, i, 751, ~len - i, BIG_CHAR);
+          do_test (0, i, 751, ~len + i, BIG_CHAR);
+          do_test (0, i, 751, ~len - buf_addr - i, BIG_CHAR);
+          do_test (0, i, 751, ~len - buf_addr + i, BIG_CHAR);
+        }
+    }
+}
+
 static void
 do_random_tests (void)
 {
@@ -221,6 +253,7 @@  test_main (void)
     do_test (page_size / 2 - i, i, i, 1, 0x9B);
 
   do_random_tests ();
+  do_overflow_tests ();
   return ret;
 }
 
diff --git a/string/test-strncat.c b/string/test-strncat.c
index 2ef917b820..0ab7541d4e 100644
--- a/string/test-strncat.c
+++ b/string/test-strncat.c
@@ -134,6 +134,66 @@  do_test (size_t align1, size_t align2, size_t len1, size_t len2,
     }
 }
 
+static void
+do_overflow_tests (void)
+{
+  size_t i, j, len;
+  const size_t one = 1;
+  CHAR *s1, *s2;
+  uintptr_t s1_addr;
+  s1 = (CHAR *) buf1;
+  s2 = (CHAR *) buf2;
+  s1_addr = (uintptr_t)s1;
+ for (j = 0; j < 200; ++j)
+      s2[j] = 32 + 23 * j % (BIG_CHAR - 32);
+ s2[200] = 0;
+  for (i = 0; i < 750; ++i) {
+    for (j = 0; j < i; ++j)
+      s1[j] = 32 + 23 * j % (BIG_CHAR - 32);
+    s1[i] = '\0';
+
+       FOR_EACH_IMPL (impl, 0)
+    {
+      s2[0] = '\0';
+      do_one_test (impl, s2, s1, SIZE_MAX - i);
+      s2[0] = '\0';
+      do_one_test (impl, s2, s1, i - s1_addr);
+      s2[0] = '\0';
+      do_one_test (impl, s2, s1, -s1_addr - i);
+      s2[0] = '\0';
+      do_one_test (impl, s2, s1, SIZE_MAX - s1_addr - i);
+      s2[0] = '\0';
+      do_one_test (impl, s2, s1, SIZE_MAX - s1_addr + i);
+    }
+
+    len = 0;
+    for (j = 8 * sizeof(size_t) - 1; j ; --j)
+      {
+        len |= one << j;
+        FOR_EACH_IMPL (impl, 0)
+          {
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, len - i);
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, len + i);
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, len - s1_addr - i);
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, len - s1_addr + i);
+
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, ~len - i);
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, ~len + i);
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, ~len - s1_addr - i);
+            s2[0] = '\0';
+            do_one_test (impl, s2, s1, ~len - s1_addr + i);
+          }
+      }
+  }
+}
+
 static void
 do_random_tests (void)
 {
@@ -316,6 +376,7 @@  test_main (void)
     }
 
   do_random_tests ();
+  do_overflow_tests ();
   return ret;
 }
 
diff --git a/string/test-strnlen.c b/string/test-strnlen.c
index 920f58e97b..f53e09263f 100644
--- a/string/test-strnlen.c
+++ b/string/test-strnlen.c
@@ -89,6 +89,38 @@  do_test (size_t align, size_t len, size_t maxlen, int max_char)
     do_one_test (impl, (CHAR *) (buf + align), maxlen, MIN (len, maxlen));
 }
 
+static void
+do_overflow_tests (void)
+{
+  size_t i, j, len;
+  const size_t one = 1;
+  uintptr_t buf_addr = (uintptr_t) buf1;
+
+  for (i = 0; i < 750; ++i)
+    {
+      do_test (0, i, SIZE_MAX - i, BIG_CHAR);
+      do_test (0, i, i - buf_addr, BIG_CHAR);
+      do_test (0, i, -buf_addr - i, BIG_CHAR);
+      do_test (0, i, SIZE_MAX - buf_addr - i, BIG_CHAR);
+      do_test (0, i, SIZE_MAX - buf_addr + i, BIG_CHAR);
+
+      len = 0;
+      for (j = 8 * sizeof(size_t) - 1; j ; --j)
+        {
+          len |= one << j;
+          do_test (0, i, len - i, BIG_CHAR);
+          do_test (0, i, len + i, BIG_CHAR);
+          do_test (0, i, len - buf_addr - i, BIG_CHAR);
+          do_test (0, i, len - buf_addr + i, BIG_CHAR);
+
+          do_test (0, i, ~len - i, BIG_CHAR);
+          do_test (0, i, ~len + i, BIG_CHAR);
+          do_test (0, i, ~len - buf_addr - i, BIG_CHAR);
+          do_test (0, i, ~len - buf_addr + i, BIG_CHAR);
+        }
+    }
+}
+
 static void
 do_random_tests (void)
 {
@@ -283,6 +315,7 @@  test_main (void)
   do_random_tests ();
   do_page_tests ();
   do_page_2_tests ();
+  do_overflow_tests ();
   return ret;
 }