linux-kernel - Re: Reading /proc/kcore causes a BUG()

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Message-Id: <20090907151422.4d42e382.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Mon, 7 Sep 2009 15:14:22 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Craig-Wood <nick@...ig-wood.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Reading /proc/kcore causes a BUG()

On Mon, 7 Sep 2009 09:38:56 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> > That's a lot of stuff for 2.6.31.  Is there some simple quickfix we can do?
> > 
> I don't like this patch. But here, my 1st version which wasn't sent out.
> -Kame

Fixed warnings. (I confirmed this patch works well on x86-64.)
==
To access vmalloc area which may have memory holes, copy_from_user is
useful. By this, 
 # cat /proc/kcore > /dev/null
will not panic.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
 fs/proc/kcore.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Index: linux-2.6.31-rc8/fs/proc/kcore.c
===================================================================
--- linux-2.6.31-rc8.orig/fs/proc/kcore.c
+++ linux-2.6.31-rc8/fs/proc/kcore.c
@@ -361,7 +361,13 @@ read_kcore(struct file *file, char __use
 				/* don't dump ioremap'd stuff! (TA) */
 				if (m->flags & VM_IOREMAP)
 					continue;
-				memcpy(elf_buf + (vmstart - start),
+				/*
+				 * we may access memory holes, then use
+				 * ex_table. checking return value just for
+				 * avoid warnings.
+				 */
+				vmsize = __copy_from_user_inatomic(
+					elf_buf + (vmstart - start),
 					(char *)vmstart, vmsize);
 			}
 			read_unlock(&vmlist_lock);

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