From mboxrd@z Thu Jan  1 00:00:00 1970
Return-path: <kexec-bounces+dwmw2=infradead.org@lists.infradead.org>
Received: from esentire.com ([64.7.150.32])
	by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux))
	id 1Kfg4E-0007yC-VS
	for kexec@lists.infradead.org; Tue, 16 Sep 2008 19:18:31 +0000
Message-ID: <48D0067F.3020007@esentire.com>
Date: Tue, 16 Sep 2008 15:18:23 -0400
From: Jonathan Steel <jon.steel@esentire.com>
MIME-Version: 1.0
Subject: [PATCH] kexec, kernel 2.6.26.5, segmentation fault in kimage_add_entry
List-Id: <kexec.lists.infradead.org>
List-Unsubscribe: <http://lists.infradead.org/mailman/listinfo/kexec>,
	<mailto:kexec-request@lists.infradead.org?subject=unsubscribe>
List-Archive: <http://lists.infradead.org/pipermail/kexec>
List-Post: <mailto:kexec@lists.infradead.org>
List-Help: <mailto:kexec-request@lists.infradead.org?subject=help>
List-Subscribe: <http://lists.infradead.org/mailman/listinfo/kexec>,
	<mailto:kexec-request@lists.infradead.org?subject=subscribe>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Sender: kexec-bounces@lists.infradead.org
Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org

A segmentation fault can occur in kimage_add_entry in kexec.c when 
loading a kernel image into memory. The fault occurs because a page is 
requested by calling kimage_alloc_page with gfp_mask GFP_KERNEL and the 
function may actually return a page with gfp_mask GFP_HIGHUSER. The high 
mem page is returned because it was swapped with the kernel page due to 
the kernel page being a page that will shortly be copied to.

This patch ensures that kimage_alloc_page returns a page that was 
created with the correct gfp flags.

--- linux-2.6.26.5.orig/kernel/kexec.c    2008-09-16 13:17:56.000000000 
-0400
+++ linux-2.6.26.5/kernel/kexec.c    2008-09-16 13:26:35.000000000 -0400
@@ -743,8 +743,15 @@ static struct page *kimage_alloc_page(st
             *old = addr | (*old & ~PAGE_MASK);
 
             /* The old page I have found cannot be a
-             * destination page, so return it.
-             */
+             * destination page, so return it if its
+             * gfp_flags honor the ones passed in.
+            */
+            if (!(gfp_mask & __GFP_HIGHMEM) &&
+                    PageHighMem(old_page)) {
+                kimage_free_pages(old_page);
+                continue;
+            }
+
             addr = old_addr;
             page = old_page;
             break;

Signed-off-by: Jonathan Steel <jon.steel@esentire.com>

Jonathan Steel

_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec