From: Phil Sutter <phil@nwl.cc>
To: Florian Westphal <fw@strlen.de>
Cc: Ren Wei <enjou1224z@gmail.com>,
netfilter-devel@vger.kernel.org, pablo@netfilter.org,
davem@davemloft.net, edumazet@google.com, pabeni@redhat.com,
horms@kernel.org, yuantan098@gmail.com, dstsmallbird@foxmail.com,
chzhengyang2023@lzu.edu.cn
Subject: Re: [PATCH nf 1/1] netfilter: xt_time: reject pre-epoch calendar matching
Date: Fri, 3 Jul 2026 13:03:43 +0200 [thread overview]
Message-ID: <akeXD_GwEFarWAuK@orbyte.nwl.cc> (raw)
In-Reply-To: <akeO-v0H9QP1psep@strlen.de>
On Fri, Jul 03, 2026 at 12:29:14PM +0200, Florian Westphal wrote:
> Phil Sutter <phil@nwl.cc> wrote:
> > > This is silly. I'm not sure this is even a bug.
> > > We're in 2026 not 1970. I really don't see why this patch is required.
> >
> > I imagined a system with broken BIOS clock which boots at epoch until
> > NTP has fixed it. Then stamp will be close to zero, no?
>
> So what? Rule won't match either way. I wish we could get somehow
> get rid of xt_time and nft_meta time matching, this was a very bad
> idea from the start.
Sure, time-based packet matching won't work on a system with wrong time,
but AIUI the patch is merely trying to prevent the unexpectedly large
lshift. It seems harmless, though:
- current_time.weekday can't exceed 7, it is assigned the result of a
modulo operation
- current_time.monthday is type u8, so worst case the kernel will
compute '1U << 255'
Cheers, Phil
next prev parent reply other threads:[~2026-07-03 11:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <cover.1782879547.git.chzhengyang2023@lzu.edu.cn>
2026-07-03 7:32 ` [PATCH nf 1/1] netfilter: xt_time: reject pre-epoch calendar matching Ren Wei
2026-07-03 9:00 ` Phil Sutter
2026-07-03 10:08 ` Florian Westphal
2026-07-03 10:15 ` Phil Sutter
2026-07-03 10:29 ` Florian Westphal
2026-07-03 11:03 ` Phil Sutter [this message]
2026-07-03 11:07 ` Pablo Neira Ayuso
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