linux-kernel - [patch] printk: fix possible printk overrun

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Message-ID: <20080225155038.GA25423@elte.hu>
Date:	Mon, 25 Feb 2008 16:50:38 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [patch] printk: fix possible printk overrun

Subject: printk: fix possible printk overrun
From: Tejun Heo <htejun@...il.com>
Date: Thu, 14 Feb 2008 10:32:07 +0900

printk recursion detection prepends message to printk_buf and offsets 
printk_buf when actual message is printed but it forgets to trim buffer 
length accordingly. This can result in overrun in extreme cases. Fix it.

[ mingo@...e.hu:

  bug was introduced by me via:

   commit 32a76006683f7b28ae3cc491da37716e002f198e
   Author: Ingo Molnar <mingo@...e.hu>
   Date:   Fri Jan 25 21:07:58 2008 +0100

       printk: make printk more robust by not allowing recursion
]

Signed-off-by: Tejun Heo <htejun@...il.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/printk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux/kernel/printk.c
===================================================================
--- linux.orig/kernel/printk.c
+++ linux/kernel/printk.c
@@ -666,7 +666,7 @@ asmlinkage int vprintk(const char *fmt, 
 	}
 	/* Emit the output into the temporary buffer */
 	printed_len += vscnprintf(printk_buf + printed_len,
-				  sizeof(printk_buf), fmt, args);
+				  sizeof(printk_buf) - printed_len, fmt, args);
 
 	/*
 	 * Copy the output into log_buf.  If the caller didn't provide
--
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