linux-kernel - Re: [PATCH RFC] random: fix syzkaller fuzzer test int overflow

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Date:   Wed, 25 Oct 2017 08:56:46 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Chen Feng <puck.chen@...ilicon.com>
Cc:     Theodore Ts'o <tytso@....edu>, zhaoyukun@...wei.com, arnd@...db.de,
        linux-kernel@...r.kernel.org, suzhuangluan@...ilicon.com,
        dan.zhao@...ilicon.com
Subject: Re: [PATCH RFC] random: fix syzkaller fuzzer test int overflow

On Wed, Oct 25, 2017 at 02:30:56PM +0800, Chen Feng wrote:
> Hi Ted,
> 
> On 2017/10/24 18:25, Theodore Ts'o wrote:
> > On Tue, Oct 24, 2017 at 11:09:27AM +0200, Greg KH wrote:
> >> On Tue, Oct 24, 2017 at 03:44:17PM +0800, Chen Feng wrote:
> >>> [pid:11940,cpu6,syz-executor][flp_ioctl]cmd[0x1]
> >>> Restart is not permit
> >>> =================================================================
> >>> UBSAN: Undefined behaviour in
> >>> kernel/linux-4.4/drivers/char/random.c:676:19
> >>> signed integer overflow:
> >>> 2147483645 + 268435455 cannot be represented in type 'int'
> >>> CPU: 4 PID: 11941 Comm: syz-executor Not tainted 4.4.76+ #2
> >>
> >> Does this also happen on 4.14-rc6?
> > 
> > No.  It was fixed in 4.8, by commit 86a574de4590: "random: strengthen
> > input validation for RNDADDTOENTCNT".
> 
> 
> I see my kernel has already merged this patch. So I don't think this patch
> can resolve the issue above.

Do you have a reproducer for this issue that we can use to test?

thanks,

greg k-h