Re: [PATCH] malloc: Fix for infinite loop in memalign/posix_memalign.

[Will Newton <will dot newton at linaro dot org>]

On 17 October 2013 00:42, Will Newton <will.newton@linaro.org> wrote:
> On 10 October 2013 13:26, Will Newton <will.newton@linaro.org> wrote:
>>
>> A very large alignment argument passed to mealign/posix_memalign
>> causes _int_memalign to enter an infinite loop. Limit the maximum
>> alignment value to the maximum representable power of two to
>> prevent this from happening.
>>
>> Changelog:
>>
>> 2013-10-10  Will Newton  <will.newton@linaro.org>
>>
>>         [BZ #16038]
>>         * malloc/hooks.c (memalign_check): Limit alignment to the
>>         maximum representable power of two.
>>         * malloc/malloc.c (__libc_memalign): Likewise.
>>         * malloc/tst-memalign.c (do_test): Add test for very
>>         large alignment values.
>>         * malloc/tst-posix_memalign.c (do_test): Likewise.
>> ---
>>  malloc/hooks.c              |  8 ++++++++
>>  malloc/malloc.c             |  8 ++++++++
>>  malloc/tst-memalign.c       | 15 +++++++++++++++
>>  malloc/tst-posix_memalign.c | 10 ++++++++++
>>  4 files changed, 41 insertions(+)
>>
>> diff --git a/malloc/hooks.c b/malloc/hooks.c
>> index 3f663bb..1dbe93f 100644
>> --- a/malloc/hooks.c
>> +++ b/malloc/hooks.c
>> @@ -361,6 +361,14 @@ memalign_check(size_t alignment, size_t bytes, const void *caller)
>>    if (alignment <= MALLOC_ALIGNMENT) return malloc_check(bytes, NULL);
>>    if (alignment <  MINSIZE) alignment = MINSIZE;
>>
>> +  /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
>> +     power of 2 and will cause overflow in the check below.  */
>> +  if (alignment > SIZE_MAX / 2 + 1)
>> +    {
>> +      __set_errno (EINVAL);
>> +      return 0;
>> +    }
>> +
>>    /* Check for overflow.  */
>>    if (bytes > SIZE_MAX - alignment - MINSIZE)
>>      {
>> diff --git a/malloc/malloc.c b/malloc/malloc.c
>> index 2938234..f1949f0 100644
>> --- a/malloc/malloc.c
>> +++ b/malloc/malloc.c
>> @@ -3026,6 +3026,14 @@ __libc_memalign(size_t alignment, size_t bytes)
>>    /* Otherwise, ensure that it is at least a minimum chunk size */
>>    if (alignment <  MINSIZE) alignment = MINSIZE;
>>
>> +  /* If the alignment is greater than SIZE_MAX / 2 + 1 it cannot be a
>> +     power of 2 and will cause overflow in the check below.  */
>> +  if (alignment > SIZE_MAX / 2 + 1)
>> +    {
>> +      __set_errno (EINVAL);
>> +      return 0;
>> +    }
>> +
>>    /* Check for overflow.  */
>>    if (bytes > SIZE_MAX - alignment - MINSIZE)
>>      {
>> diff --git a/malloc/tst-memalign.c b/malloc/tst-memalign.c
>> index 1c59752..b8eec9e 100644
>> --- a/malloc/tst-memalign.c
>> +++ b/malloc/tst-memalign.c
>> @@ -70,6 +70,21 @@ do_test (void)
>>
>>    free (p);
>>
>> +  errno = 0;
>> +
>> +  /* Test to expose integer overflow in malloc internals from BZ #16038.  */
>> +  p = memalign (-1, pagesize);
>> +
>> +  save = errno;
>> +
>> +  if (p != NULL)
>> +    merror ("memalign (-1, pagesize) succeeded.");
>> +
>> +  if (p == NULL && save != EINVAL)
>> +    merror ("memalign (-1, -pagesize) errno is not set correctly");
>> +
>> +  free (p);
>> +
>>    /* A zero-sized allocation should succeed with glibc, returning a
>>       non-NULL value.  */
>>    p = memalign (sizeof (void *), 0);
>> diff --git a/malloc/tst-posix_memalign.c b/malloc/tst-posix_memalign.c
>> index 27c0dd2..7f34e37 100644
>> --- a/malloc/tst-posix_memalign.c
>> +++ b/malloc/tst-posix_memalign.c
>> @@ -65,6 +65,16 @@ do_test (void)
>>
>>    p = NULL;
>>
>> +  /* Test to expose integer overflow in malloc internals from BZ #16038.  */
>> +  ret = posix_memalign (&p, -1, pagesize);
>> +
>> +  if (ret != EINVAL)
>> +    merror ("posix_memalign (&p, -1, pagesize) succeeded.");
>> +
>> +  free (p);
>> +
>> +  p = NULL;
>> +
>>    /* A zero-sized allocation should succeed with glibc, returning zero
>>       and setting p to a non-NULL value.  */
>>    ret = posix_memalign (&p, sizeof (void *), 0);
>> --
>> 1.8.1.4
>>
>
> Ping?

Ping? Any further comments on this or should I go ahead and commit?

Thanks,

-- 
Will Newton
Toolchain Working Group, Linaro