ping?
On Thu, 2013-08-29 at 14:47 -0700, Joe Perches wrote:
> This sequence can return non-zeroed memory from the
> padding area of the original allocation.
>
> ptr = kzalloc(foo, GFP_KERNEL);
> if (!ptr)
> ...
> new_ptr = krealloc(ptr, foo + bar, GFP_KERNEL | __GFP_ZERO);
>
> If the realloc size is within the first actual allocation
> then the additional memory is not zeroed.
>
> If the realloc size is not within the original allocation
> size, any non-zeroed padding from the original allocation
> is overwriting newly allocated zeroed memory.
>
> Maybe someone more familiar with the alignment & padding can
> add the proper memset(,0,) for the __GFP_ZERO cases and also
> optimize kmalloc_track_caller to not use __GFP_ZERO, memcpy
> the current (non padded) size and zero the newly returned
> remainder if necessary.
>
> from: mm/util.c
> ---------------------------
> static __always_inline void *__do_krealloc(const void *p, size_t new_size,
> gfp_t flags)
> {
> void *ret;
> size_t ks = 0;
>
> if (p)
> ks = ksize(p);
>
> if (ks >= new_size)
> return (void *)p;
>
> ret = kmalloc_track_caller(new_size, flags);
> if (ret && p)
> memcpy(ret, p, ks);
>
> return ret;
> }
>
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