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Date: Thu, 10 Nov 2016 07:57:12 +0100
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jann Horn <jann@thejh.net>
Cc: Arnd Bergmann <arnd@arndb.de>,
        Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
        linux-kernel@vger.kernel.org, linux-parport@lists.infradead.org,
        Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH v2] ppdev: fix double-free of pp->pdev->name
Message-ID: <20161110065712.GC29860@kroah.com>
References: <1477865964-4497-1-git-send-email-jann@thejh.net>
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On Sun, Oct 30, 2016 at 11:19:24PM +0100, Jann Horn wrote:
> free_pardevice() is called by parport_unregister_device() and already frees
> pp->pdev->name, don't try to do it again.
> 
> This bug causes kernel crashes.
> 
> I found and verified this with KASAN and some added pr_emerg()s:
> 
> [   60.316568] pp_release: pp->pdev->name == ffff88039cb264c0
> [   60.316692] free_pardevice: freeing par_dev->name at ffff88039cb264c0
> [   60.316706] pp_release: kfree(ffff88039cb264c0)
> [   60.316714] ==========================================================
> [   60.316722] BUG: Double free or freeing an invalid pointer
> [   60.316731] Unexpected shadow byte: 0xFB
> [   60.316801] Object at ffff88039cb264c0, in cache kmalloc-32 size: 32
> [   60.316813] Allocated:
> [   60.316824] PID = 1695
> [   60.316869] Freed:
> [   60.316880] PID = 1695
> [   60.316935] ==========================================================
> 
> Signed-off-by: Jann Horn <jann@thejh.net>
> ---
>  drivers/char/ppdev.c | 3 ---
>  1 file changed, 3 deletions(-)

Sudip, I need an ack here before I can take this...