Re: [dpdk-stable] [dpdk-dev] [PATCH v3] mem: fix the alloc size roundup overflow

[David Marchand <david.marchand@redhat.com>]

On Thu, May 7, 2020 at 10:03 AM Bing Zhao <bingz@mellanox.com> wrote:
>
> The size checking is done in the caller. The size parameter is an
> unsigned (64b wide) right now, so the comparison with zero should be
> enough in most cases. But it won't help in the following case.
> If the allocating request input a huge number by mistake, e.g., some
> overflow after the calculation (especially subtraction), the checking
> in the caller will succeed since it is not zero. Indeed, there is not
> enough space in the system to support such huge memory allocation.
> Usually it will return failure in the following code. But if the
> input size is just a little smaller than the UINT64_MAX, like -2 in
> signed type.
> The roundup will cause an overflow and then "reset" the size to 0,
> and then only a header (128B now) with zero length will be returned.
> The following will be the previous allocation header.
> It should be OK in most cases if the application won't access the
> memory body. Or else, some critical issue will be caused and not easy
> to debug. So this issue should be prevented at the beginning, like
> other big size failure, NULL pointer should be returned also.
>
> Fixes: fdf20fa7bee9 ("add prefix to cache line macros")
> Cc: stable@dpdk.org
>
> Signed-off-by: Bing Zhao <bingz@mellanox.com>

Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

Applied, thanks.


-- 
David Marchand