From: Eric Biggers <ebiggers3@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org, keyrings@vger.kernel.org,
mark.rutland@arm.com, ebiggers@google.com
Subject: Re: [PATCH RESEND net-next v2] KEYS: DNS: limit the length of option strings
Date: Tue, 17 Apr 2018 11:23:40 -0700 [thread overview]
Message-ID: <20180417182340.GB9237@gmail.com> (raw)
In-Reply-To: <20180417.134316.1413649044013070735.davem@davemloft.net>
On Tue, Apr 17, 2018 at 01:43:16PM -0400, David Miller wrote:
> From: Eric Biggers <ebiggers3@gmail.com>
> Date: Mon, 16 Apr 2018 14:29:22 -0700
>
> > From: Eric Biggers <ebiggers@google.com>
> >
> > Adding a dns_resolver key whose payload contains a very long option name
> > resulted in that string being printed in full. This hit the WARN_ONCE()
> > in set_precision() during the printk(), because printk() only supports a
> > precision of up to 32767 bytes:
> >
> > precision 1000000 too large
> > WARNING: CPU: 0 PID: 752 at lib/vsprintf.c:2189 vsnprintf+0x4bc/0x5b0
> >
> > Fix it by limiting option strings (combined name + value) to a much more
> > reasonable 128 bytes. The exact limit is arbitrary, but currently the
> > only recognized option is formatted as "dnserror=%lu" which fits well
> > within this limit.
> >
> > Also ratelimit the printks.
> >
> > Reproducer:
> >
> > perl -e 'print "#", "A" x 1000000, "\x00"' | keyctl padd dns_resolver desc @s
> >
> > This bug was found using syzkaller.
> >
> > Reported-by: Mark Rutland <mark.rutland@arm.com>
> > Fixes: 4a2d789267e0 ("DNS: If the DNS server returns an error, allow that to be cached [ver #2]")
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
>
> Applied, thanks.
Can you queue this up for stable too? syzbot has been hitting this on older
kernel versions.
Eric
next prev parent reply other threads:[~2018-04-17 18:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-16 21:29 [PATCH RESEND net-next v2] KEYS: DNS: limit the length of option strings Eric Biggers
2018-04-17 17:43 ` David Miller
2018-04-17 18:23 ` Eric Biggers [this message]
2018-04-17 18:24 ` David Miller
2018-04-17 18:37 ` Eric Biggers
2018-04-17 18:52 ` David Miller
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