linux-kernel - [BUGFIX][PATCH 1/3] unmap vmalloc area after hide it

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Date:	Mon, 3 Aug 2009 20:15:57 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Mike Smith <scgtrp@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	bugzilla-daemon@...zilla.kernel.org,
	bugme-daemon@...zilla.kernel.org,
	Amerigo Wang <xiyou.wangcong@...il.com>,
	linux-kernel@...r.kernel.org
Subject: [BUGFIX][PATCH 1/3] unmap vmalloc area after hide it

This is necessary to garantee sane access of vread/vwrite.

==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

vmap area should be purged after vm_struct is removed from the list
because vread/vwrite etc...believes the range is valid while it's on
vm_struct list.

Reviewed-by: WANG Cong <xiyou.wangcong@...il.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
 mm/vmalloc.c |   14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Index: linux-2.6.31-rc4/mm/vmalloc.c
===================================================================
--- linux-2.6.31-rc4.orig/mm/vmalloc.c	2009-07-31 15:51:56.000000000 +0900
+++ linux-2.6.31-rc4/mm/vmalloc.c	2009-07-31 15:52:42.000000000 +0900
@@ -1256,17 +1256,21 @@
 	if (va && va->flags & VM_VM_AREA) {
 		struct vm_struct *vm = va->private;
 		struct vm_struct *tmp, **p;
-
-		vmap_debug_free_range(va->va_start, va->va_end);
-		free_unmap_vmap_area(va);
-		vm->size -= PAGE_SIZE;
-
+		/*
+		 * remove from list and disallow access to this vm_struct
+		 * before unmap. (address range confliction is maintained by
+		 * vmap.)
+		 */
 		write_lock(&vmlist_lock);
 		for (p = &vmlist; (tmp = *p) != vm; p = &tmp->next)
 			;
 		*p = tmp->next;
 		write_unlock(&vmlist_lock);
 
+		vmap_debug_free_range(va->va_start, va->va_end);
+		free_unmap_vmap_area(va);
+		vm->size -= PAGE_SIZE;
+
 		return vm;
 	}
 	return NULL;

--
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