netdev - Re: [PATCH] tcp: Replace infinite loop on recvmsg bug with proper crash

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Message-ID: <CAODwPW-636Sn3B4CYajvrgccXxresZwPLg2UFz6xDDk9-FfTYQ@mail.gmail.com>
Date:	Tue, 6 Nov 2012 17:51:19 -0800
From:	Julius Werner <jwerner@...omium.org>
To:	Dave Jones <davej@...hat.com>,
	Julius Werner <jwerner@...omium.org>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Patrick McHardy <kaber@...sh.net>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	James Morris <jmorris@...ei.org>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	"David S. Miller" <davem@...emloft.net>,
	Sameer Nanda <snanda@...omium.org>,
	Mandeep Singh Baines <msb@...omium.org>,
	Eric Dumazet <edumazet@...omium.org>
Subject: Re: [PATCH] tcp: Replace infinite loop on recvmsg bug with proper crash

> We've had reports of this WARN against the Fedora kernel for a while.
> Had this been immediately followed by a BUG(), we'd have never seen those traces at all,
> and just got "my machine just locked up" reports instead.
>
> The proper fix here is to find out why we're getting into this state.

Are you sure you don't mean the WARN below that ("recvmsg bug 2")
instead? I don't think this one can happen without eventually running
into the syslog overflow issue I described.

I agree that the underlying cause must be fixed too, but as we will
always have bugs in the kernel I think proper handling when it does
happen is also important (and filling the hard disk with junk is
obviously not the best approach). If you think a full panic is too
extreme, I have an alternative version of this patch that logs the
WARN once, closes the socket, and returns EBADFD from the syscall...
would you think that is more appropriate?
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