printk: fix possible printk overrun

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 32a7600668
   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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Tejun Heo 2008-02-14 10:32:07 +09:00 committed by Linus Torvalds
parent bfa274e243
commit cf3680b90c

View File

@ -666,7 +666,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
}
/* 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