Re: [PATCH v3] Fix integer overflows in internal memalign and malloc functions [BZ #22343]

[Carlos O'Donell <carlos at redhat dot com>]

On 01/18/2018 08:47 AM, Arjun Shankar wrote:
> When posix_memalign is called with an alignment less than MALLOC_ALIGNMENT
> and a requested size close to SIZE_MAX, it falls back to malloc code
> (because the alignment of a block returned by malloc is sufficient to
> satisfy the call).  In this case, an integer overflow in _int_malloc leads
> to posix_memalign incorrectly returning successfully.
> 
> Upon fixing this and writing a somewhat thorough regression test, it was
> discovered that when posix_memalign is called with an alignment larger than
> MALLOC_ALIGNMENT (so it uses _int_memalign instead) and a requested size
> close to SIZE_MAX, a different integer overflow in _int_memalign leads to
> posix_memalign incorrectly returning successfully.
> 
> Both integer overflows affect other memory allocation functions that use
> _int_malloc (one affected malloc in x86) or _int_memalign as well.
> 
> This commit fixes both integer overflows.  In addition to this, it adds a
> regression test to guard against false successful allocations by the
> following memory allocation functions when called with too-large allocation
> sizes and, where relevant, various valid alignments:
> malloc, realloc, calloc, reallocarray, memalign, posix_memalign,
> aligned_alloc, valloc, and pvalloc.
> 
> ChangeLog:
> 
> 2018-01-18  Arjun Shankar  <arjun@redhat.com>
> 
> 	[BZ #22343]
> 	* malloc/malloc.c (checked_request2size): call REQUEST_OUT_OF_RANGE
> 	after padding.
> 	(_int_memalign): check for integer overflow before calling
> 	_int_malloc.
> 	* malloc/tst-malloc-too-large.c: New test.
> 	* malloc/Makefile: Add tst-malloc-too-large.
> ---
> v1 discussion: https://sourceware.org/ml/libc-alpha/2018-01/msg00133.html
> v2 discussion: https://sourceware.org/ml/libc-alpha/2018-01/msg00582.html
> v3:
>  * correctly indents checked_request2size
>  * removes timeout definition in tst-malloc-too-large (20 sec is default)
LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

-- 
Cheers,
Carlos.