linux-kernel - Re: [PATCH] Fix kunmap() argument in sg_miter

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Message-ID: <20081115123916.0d83a89e@infradead.org>
Date:	Sat, 15 Nov 2008 12:39:16 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	linux-kernel@...r.kernel.org, htejun@...il.com,
	akpm@...ux-foundation.org, jens.axboe@...cle.com
Subject: Re: [PATCH] Fix kunmap() argument in sg_miter_stop

On Sat, 15 Nov 2008 20:15:15 +0000 (GMT)
Hugh Dickins <hugh@...itas.com> wrote:

> On Sat, 15 Nov 2008, Arjan van de Ven wrote:
> > >From fd5530ac75a919a20bf7951e90a2b12323e9c0a0 Mon Sep 17 00:00:00
> > >2001
> > From: Arjan van de Ven <arjan@...ux.intel.com>
> > Date: Sat, 15 Nov 2008 11:23:58 -0800
> > Subject: [PATCH] Fix kunmap() argument in sg_miter_stop
> > 
> > kunmap() takes as argument the struct page that orginally got
> > kmap()'d, however the sg_miter_stop() function passed it the kernel
> > virtual address instead, resulting in "kernel BUG at
> > arch/x86/mm/highmem_32.c:115!"
> 
> Your patch looks like a good fix to me, but I don't get how its bug
> would manifest as highmem_32.c:115 - that's a check in
> kunmap_atomic(), whereas you're fixing a bad address to kunmap().

patch with updated description:

>From 979d181d6199f639ba78c5eadf85857f6a9f3f89 Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@...ux.intel.com>
Date: Sat, 15 Nov 2008 11:23:58 -0800
Subject: [PATCH] Fix kunmap() argument in sg_miter_stop

kunmap() takes as argument the struct page that orginally got kmap()'d,
however the sg_miter_stop() function passed it the kernel virtual address
instead, resulting in weird stuff.

Somehow I ended up fixing this bug by accident while looking for a bug
in the same area.

Reported-by: kerneloops.org
CC: htejun@...il.com

Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
---
 lib/scatterlist.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 8d2688f..b7b449d 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -395,7 +395,7 @@ void sg_miter_stop(struct sg_mapping_iter *miter)
 			WARN_ON(!irqs_disabled());
 			kunmap_atomic(miter->addr, KM_BIO_SRC_IRQ);
 		} else
-			kunmap(miter->addr);
+			kunmap(miter->page);
 
 		miter->page = NULL;
 		miter->addr = NULL;
-- 
1.6.0.3



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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