linux-kernel - [ 029/184] kernel/resource.c: fix stack overflow in

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Message-Id: <20130604172131.510859183@1wt.eu>
Date:	Tue, 04 Jun 2013 19:21:59 +0200
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	T Makphaibulchoke <tmac@...com>,
	Paul Gortmaker <paul.gortmaker@...il.com>,
	Wei Yang <weiyang@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Willy Tarreau <w@....eu>
Subject: [ 029/184] kernel/resource.c: fix stack overflow in

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------
 __reserve_region_with_split()

From: T Makphaibulchoke <tmac@...com>

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@...com>
Reviewed-by: Ram Pai <linuxram@...ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@...il.com>
Cc: Wei Yang <weiyang@...ux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Jiri Slaby <jslaby@...e.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 kernel/resource.c | 50 ++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 38 insertions(+), 12 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index fb11a58..207915a 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -533,6 +533,7 @@ 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;
@@ -542,21 +543,46 @@ 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,
-- 
1.7.12.2.21.g234cd45.dirty



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