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Subject[patch] printk: fix possible printk overrun
Subject: printk: fix possible printk overrun
From: Tejun Heo <htejun@gmail.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@elte.hu:

bug was introduced by me via:

commit 32a76006683f7b28ae3cc491da37716e002f198e
Author: Ingo Molnar <mingo@elte.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@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.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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