linux-kernel - Re: [PATCH 00/14] Fix wrong %pF and %pS printk format specifier usages

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Message-ID: <20170908172528.qc2vdtxzqh777k6o@intel.com>
Date:   Fri, 8 Sep 2017 10:25:29 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Helge Deller <deller@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 00/14] Fix wrong %pF and %pS printk format specifier
 usages

On Fri, Sep 08, 2017 at 03:18:30PM +0900, Sergey Senozhatsky wrote:
> if the addr is not in kernel .text, then try dereferencing it and check
> if the dereferenced addr is in kernel .text.

If it really is a function pointer, then we know that it is safe
to dereference. But if it isn't, then maybe not?

If it is a function pointer then dereferening will indeed give
us a .text address. But if it isn't, it might still give us a
.text address (we could reduce the probability of a false hit
by checking that the .text address was exactly on a symbol with
no offset ... but data values that happen to be the addresses of
function entry points are possible).

-Tony