linux-kernel - [PATCH] Fix x86 iounmap() calling ioremap_change

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Message-ID: <4774297B.1060305@myri.com>
Date:	Thu, 27 Dec 2007 17:38:51 -0500
From:	Loic Prylli <loic@...i.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] Fix x86 iounmap() calling ioremap_change_attr() with a size
 that's too big.

The get_vm_area() allocates one extra guard page, and stores the augmented
size in area->size. But the ioremap/iounmap code on x86 relies on finding
the original size in area->size (otherwise it does change the attribute
of some random device in the linear-map by using a wrong size in
ioremap_change_attr() ). The problem is avoided by not using an extra guard
page for VM_IOREMAP allocations (if somebody can think of an easy way to
store the original size across ioremap()/iounmap() calls, that could be
a more elegant solution).

Signed-off-by: Loic Prylli <loic@...i.com>
---
 mm/vmalloc.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index af77e17..efd0093 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -196,9 +196,10 @@ static struct vm_struct *__get_vm_area_node(unsigned long size, unsigned long fl
 		return NULL;

 	/*
-	 * We always allocate a guard page.
+	 * We allocate a guard page (except for ioremap() which relies on area->size == size)
 	 */
-	size += PAGE_SIZE;
+	if (!(flags & VM_IOREMAP))
+	    size += PAGE_SIZE;

 	write_lock(&vmlist_lock);
 	for (p = &vmlist; (tmp = *p) != NULL ;p = &tmp->next) {
-- 
1.5.2.2

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