linux-kernel - Re: [PATCH] vsprintf: protect kernel from panic due to non-canonical pointer dereference

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Message-ID: <Y02sENwhtpsx5yhP@smile.fi.intel.com>
Date:   Mon, 17 Oct 2022 22:25:04 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jane Chu <jane.chu@...cle.com>
Cc:     pmladek@...e.com, rostedt@...dmis.org, senozhatsky@...omium.org,
        linux@...musvillemoes.dk, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vsprintf: protect kernel from panic due to non-canonical
 pointer dereference

On Mon, Oct 17, 2022 at 01:16:11PM -0600, Jane Chu wrote:
> While debugging a separate issue, it was found that an invalid string
> pointer could very well contain a non-canical address, such as
> 0x7665645f63616465. In that case, this line of defense isn't enough
> to protect the kernel from crashing due to general protection fault
> 
> 	if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
>                 return "(efault)";
> 
> So instead, use kern_addr_valid() to validate the string pointer.

How did you check that value of the (invalid string) pointer?


-- 
With Best Regards,
Andy Shevchenko