linux-kernel - [PATCH v4 1/6] resources: ensure alignment callback doesn't allocate below available start

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Date:	Thu, 14 Oct 2010 17:18:26 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Bob Picco <bpicco@...hat.com>,
	Brian Bloniarz <phunge0@...mail.com>,
	Charles Butterfield <charles.butterfield@...tcentury.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	linux-pci@...r.kernel.org,
	"Horst H. von Brand" <vonbrand@....utfsm.cl>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Stefan Becker <chemobejk@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org>,
	Leann Ogasawara <leann.ogasawara@...onical.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v4 1/6] resources: ensure alignment callback doesn't allocate
	below available start


The alignment callback returns a proposed location, which may have been
adjusted to avoid ISA aliases or for other architecture-specific reasons.
We already had a check ("tmp.start < tmp.end") to make sure the callback
doesn't return a location above the available area.

This patch adds a check to make sure the callback doesn't return something
*below* the available area, as may happen if the callback tries to allocate
top-down.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@...com>
---

 kernel/resource.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)


diff --git a/kernel/resource.c b/kernel/resource.c
index 7b36976..ace2269 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -371,6 +371,7 @@ static int find_resource(struct resource *root, struct resource *new,
 {
 	struct resource *this = root->child;
 	struct resource tmp = *new;
+	resource_size_t start;
 
 	tmp.start = root->start;
 	/*
@@ -391,8 +392,13 @@ static int find_resource(struct resource *root, struct resource *new,
 		if (tmp.end > max)
 			tmp.end = max;
 		tmp.start = ALIGN(tmp.start, align);
-		if (alignf)
-			tmp.start = alignf(alignf_data, &tmp, size, align);
+		if (alignf) {
+			start = alignf(alignf_data, &tmp, size, align);
+			if (tmp.start <= start && start <= tmp.end)
+				tmp.start = start;
+			else
+				tmp.start = tmp.end;
+		}
 		if (tmp.start < tmp.end && tmp.end - tmp.start >= size - 1) {
 			new->start = tmp.start;
 			new->end = tmp.start + size - 1;

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