netdev - Re: Deadlock with icmpv6fuzz

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Message-ID: <adafxisjzel.fsf@cisco.com>
Date:	Thu, 05 Feb 2009 14:24:02 -0800
From:	Roland Dreier <rdreier@...co.com>
To:	Eric Sesterhenn <snakebyte@....de>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	yoshfuji@...ux-ipv6.org
Subject: Re: Deadlock with icmpv6fuzz

 > [ 2880.044328] icmpv6fuzz: page allocation failure. order:9, mode:0x40d0
 > [ 2880.044495] Pid: 10968, comm: icmpv6fuzz Not tainted
 > 2.6.29-rc3-00580-ga2fe994-dirty #239
 > [ 2880.044694] Call Trace:
 > [ 2880.044802]  [<c016886a>] __alloc_pages_internal+0x38e/0x3aa
 > [ 2880.044954]  [<c016889a>] __get_free_pages+0x14/0x24
 > [ 2880.071336]  [<c018412c>] __kmalloc+0x2e/0x122
 > [ 2880.071589]  [<c06fa227>] ipv6_flowlabel_opt+0x1e0/0x7b1
 > [ 2880.092922]  [<c06e8c9e>] ipv6_setsockopt+0xa0f/0xb89

>From a quick scan of the code, it looks as if optlen is never sanity
checked in the case of setsockopt(IPV6_FLOWLABEL_MGR), and
ipv6_flowlabel_opt() calls into fl_create() with whatever value
userspace passes in, which then pretty much does kmalloc(optlen).
So if icmpv6fuzz passes some big random value, it can cause this failure.

I don't know what the appropriate limit should be, so no patch, sorry.

 - R.
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