[dpdk-stable] patch 'malloc: fix end for bounded elements' has been queued to LTS release 16.11.5

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to LTS release 16.11.5

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 01/28/18. So please
shout if anyone has objections.

Thanks.

Luca Boccassi

---
>From 8d84c383b7262434ff8e93e03be60fdb2a3e07db Mon Sep 17 00:00:00 2001
From: Anatoly Burakov <anatoly.burakov at intel.com>
Date: Thu, 21 Dec 2017 16:54:24 +0000
Subject: [PATCH] malloc: fix end for bounded elements

[ upstream commit 20d2159d4640a1844a5856d8d8df86cf0b24b7c1 ]

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")

Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
---
 lib/librte_eal/common/malloc_elem.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/librte_eal/common/malloc_elem.c b/lib/librte_eal/common/malloc_elem.c
index 77a86151b..e2bd3ac21 100644
--- a/lib/librte_eal/common/malloc_elem.c
+++ b/lib/librte_eal/common/malloc_elem.c
@@ -98,6 +98,7 @@ elem_start_pt(struct malloc_elem *elem, size_t size, unsigned align,
 	if ((new_data_start & bmask) != ((end_pt - 1) & bmask)) {
 		end_pt = RTE_ALIGN_FLOOR(end_pt, bound);
 		new_data_start = RTE_ALIGN_FLOOR((end_pt - size), align);
+		end_pt = new_data_start + size;
 		if (((end_pt - 1) & bmask) != (new_data_start & bmask))
 			return NULL;
 	}
-- 
2.14.2