Re: [dpdk-dev] [PATCH] eal: fix end for bounded malloc elements

[Thomas Monjalon <thomas@monjalon.net>]

21/12/2017 17:54, Anatoly Burakov:
> In cases when alignment is bigger than boundary, we may incorrectly
> calculate end of a bounded malloc element.
> 
> Consider this: suppose we are allocating a bounded malloc element
> that should be of 128 bytes in size, bounded to 128 bytes and
> aligned on a 256-byte boundary. Suppose our malloc element ends
> at 0x140 - that is, 256 plus one cacheline.
> 
> So, right at the start, we are aligning our new_data_start to
> include the required element size, and to be aligned on a specified
> boundary - so new_data_start becomes 0. This fails the following
> bounds check, because our element cannot go above 128 bytes from
> the start, and we are at 320. So, we enter the bounds handling
> branch.
> 
> While we're in there, we are aligning end_pt to our boundedness
> requirement of 128 byte, and end up with 0x100 (since 256 is
> 128-byte aligned). We recalculate new_data_size and it stays at
> 0, however our end is at 0x100, which is beyond the 128 byte
> boundary, and we report inability to reserve a bounded element
> when we could have.
> 
> This patch adds an end_pt recalculation after new_data_start
> adjustment - we already know that size <= bound, so we can do it
> safely - and we then correctly report that we can, in fact, try
> using this element for bounded malloc allocation.
> 
> Fixes: fafcc11985a2 ("mem: rework memzone to be allocated by malloc")
> Cc: sergio.gonzalez.monroy@intel.com
> Cc: stable@dpdk.org
> Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>

It looks to be a headache, but as the maintainer of DPDK memory,
I trust you :)

Applied, thanks