linux-kernel - [PATCH v5 4/9] resources: handle overflow when aligning start of available area

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Date:	Tue, 26 Oct 2010 15:41:28 -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>,
	Ingo Molnar <mingo@...e.hu>, linux-pci@...r.kernel.org,
	"Horst H. von Brand" <vonbrand@....utfsm.cl>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Stefan Becker <chemobejk@...il.com>,
	Chuck Ebbert <cebbert@...hat.com>,
	Fabrice Bellet <fabrice@...let.info>,
	Yinghai Lu <yinghai@...nel.org>,
	Leann Ogasawara <leann.ogasawara@...onical.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v5 4/9] resources: handle overflow when aligning start of
	available area


If tmp.start is near ~0, ALIGN(tmp.start) may overflow, which would
make us think there's more available space than there really is.  We
would likely return something that conflicts with a previous resource,
which would cause a failure when allocate_resource() requests the newly-
allocated region.

Reference: https://bugzilla.redhat.com/show_bug.cgi?id=646027
Reported-by: Fabrice Bellet <fabrice@...let.info>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@...com>
---

 kernel/resource.c |   21 +++++++++++++--------
 1 files changed, 13 insertions(+), 8 deletions(-)


diff --git a/kernel/resource.c b/kernel/resource.c
index 89d5041..e15b922 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -392,7 +392,7 @@ static int find_resource(struct resource *root, struct resource *new,
 			 void *alignf_data)
 {
 	struct resource *this = root->child;
-	struct resource tmp = *new, alloc;
+	struct resource tmp = *new, avail, alloc;
 
 	tmp.start = root->start;
 	/*
@@ -410,14 +410,19 @@ static int find_resource(struct resource *root, struct resource *new,
 			tmp.end = root->end;
 
 		resource_clip(&tmp, min, max);
-		tmp.start = ALIGN(tmp.start, align);
 
-		alloc.start = alignf(alignf_data, &tmp, size, align);
-		alloc.end = alloc.start + size - 1;
-		if (resource_contains(&tmp, &alloc)) {
-			new->start = alloc.start;
-			new->end = alloc.end;
-			return 0;
+		/* Check for overflow after ALIGN() */
+		avail = *new;
+		avail.start = ALIGN(tmp.start, align);
+		avail.end = tmp.end;
+		if (avail.start >= tmp.start) {
+			alloc.start = alignf(alignf_data, &avail, size, align);
+			alloc.end = alloc.start + size - 1;
+			if (resource_contains(&avail, &alloc)) {
+				new->start = alloc.start;
+				new->end = alloc.end;
+				return 0;
+			}
 		}
 		if (!this)
 			break;

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