[ 3.5.y.z extended stable ] Patch "kernel/resource.c: fix stack overflow in" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    kernel/resource.c: fix stack overflow in

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From eada91d3628ac4496b6561b02036a23f2fcf652e Mon Sep 17 00:00:00 2001
From: T Makphaibulchoke <tmac at hp.com>
Date: Thu, 4 Oct 2012 17:16:55 -0700
Subject: [PATCH] kernel/resource.c: fix stack overflow in
 __reserve_region_with_split()

commit 4965f5667f36a95b41cda6638875bc992bd7d18b upstream.

Using a recursive call add a non-conflicting region in
__reserve_region_with_split() could result in a stack overflow in the case
that the recursive calls are too deep.  Convert the recursive calls to an
iterative loop to avoid the problem.

Tested on a machine containing 135 regions.  The kernel no longer panicked
with stack overflow.

Also tested with code arbitrarily adding regions with no conflict,
embedding two consecutive conflicts and embedding two non-consecutive
conflicts.

Signed-off-by: T Makphaibulchoke <tmac at hp.com>
Reviewed-by: Ram Pai <linuxram at us.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker at gmail.com>
Cc: Wei Yang <weiyang at linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Jiri Slaby <jslaby at suse.cz>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 kernel/resource.c |   50 ++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 38 insertions(+), 12 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index e1d2b8e..7de982e 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -758,6 +758,7 @@ static void __init __reserve_region_with_split(struct resource *root,
 	struct resource *parent = root;
 	struct resource *conflict;
 	struct resource *res = kzalloc(sizeof(*res), GFP_ATOMIC);
+	struct resource *next_res = NULL;

 	if (!res)
 		return;
@@ -767,21 +768,46 @@ static void __init __reserve_region_with_split(struct resource *root,
 	res->end = end;
 	res->flags = IORESOURCE_BUSY;

-	conflict = __request_resource(parent, res);
-	if (!conflict)
-		return;
+	while (1) {

-	/* failed, split and try again */
-	kfree(res);
+		conflict = __request_resource(parent, res);
+		if (!conflict) {
+			if (!next_res)
+				break;
+			res = next_res;
+			next_res = NULL;
+			continue;
+		}

-	/* conflict covered whole area */
-	if (conflict->start <= start && conflict->end >= end)
-		return;
+		/* conflict covered whole area */
+		if (conflict->start <= res->start &&
+				conflict->end >= res->end) {
+			kfree(res);
+			WARN_ON(next_res);
+			break;
+		}
+
+		/* failed, split and try again */
+		if (conflict->start > res->start) {
+			end = res->end;
+			res->end = conflict->start - 1;
+			if (conflict->end < end) {
+				next_res = kzalloc(sizeof(*next_res),
+						GFP_ATOMIC);
+				if (!next_res) {
+					kfree(res);
+					break;
+				}
+				next_res->name = name;
+				next_res->start = conflict->end + 1;
+				next_res->end = end;
+				next_res->flags = IORESOURCE_BUSY;
+			}
+		} else {
+			res->start = conflict->end + 1;
+		}
+	}

-	if (conflict->start > start)
-		__reserve_region_with_split(root, start, conflict->start-1, name);
-	if (conflict->end < end)
-		__reserve_region_with_split(root, conflict->end+1, end, name);
 }

 void __init reserve_region_with_split(struct resource *root,
--
1.7.9.5