netdev - Re: [PATCH] XFRM,IPv6: initialize ip6_dst_blackhole_ops.kmem

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Date:	Thu, 25 Sep 2008 11:21:31 +0200
From:	"Benjamin Thery" <ben.thery@...il.com>
To:	"Arnaud Ebalard" <arno@...isbad.org>
Cc:	netdev@...r.kernel.org, "David Miller" <davem@...emloft.net>,
	"Herbert Xu" <herbert@...dor.apana.org.au>,
	"YOSHIFUJI Hideaki / 吉藤英明" 
	<yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH] XFRM,IPv6: initialize ip6_dst_blackhole_ops.kmem_cachep

On Tue, Sep 23, 2008 at 18:21, Arnaud Ebalard <arno@...isbad.org> wrote:
> Hi,
>
> With the switch to a default value of 1 for xfrm_larval_drop in commit
> 28faa979746b2352cd78a376bf9f52db953bda46 (ipsec: Make xfrm_larval_drop
> default to 1), what seems to be a bug manage to surface on one of my
> test box running today's net-next (*).
>
> When xfrm_tmpl_resolve() returns -EAGAIN in __xfrm_lookup(), the caller
> is returned -EREMOTE and is expected to install a blackhole route. For
> IPv6, the call to dst_alloc(&ip6_dst_blackhole_ops) performed by
> ip6_dst_blackhole() produces the error provided below, because
> kmem_cachep attribute seems to be uninitialized. This does not happen
> when xfrm_larval_drop is set to 0.
>
> The patch below againt today's net-next fixes the issue but I am unable
> to tell if it is the best way (or even a decent way) to do it.
>
> Note that I am able to reproduce the issue on current 2.6.27-rc7 by
> forcing xfrm_larval_drop to 1. The patch below solves the problem,
> i.e. this may be a candidate for 2.6.27-rc8 (if correct).
>
> I may have missed something. Comments welcome.
>
> Cheers,
>
> a+
>
> (*): with the small MIGRATE patch David commented some days ago applied
>     on top of it. No interaction expected.
>
>
>
> From: Arnaud Ebalard <arno@...isbad.org>
> Date: Tue, 23 Sep 2008 16:59:04 +0200
> Subject: [PATCH] XFRM,IPv6: initialize ip6_dst_blackhole_ops.kmem_cachep
>
> ip6_dst_blackhole_ops.kmem_cachep is not expected to be NULL (i.e. to
> be initialized) when dst_alloc() is called from ip6_dst_blackhole().
> Otherwise, it results in the following (xfrm_larval_drop is now set to
> 1 by default):
>
> [   78.697642] Unable to handle kernel paging request for data at address 0x0000004c
> [   78.703449] Faulting instruction address: 0xc0097f54
> [   78.786896] Oops: Kernel access of bad area, sig: 11 [#1]
> [   78.792791] PowerMac
> [   78.798383] Modules linked in: btusb usbhid bluetooth b43 mac80211 cfg80211 ehci_hcd ohci_hcd sungem sungem_phy usbcore ssb
> [   78.804263] NIP: c0097f54 LR: c0334a28 CTR: c002d430
> [   78.809997] REGS: eef19ad0 TRAP: 0300   Not tainted  (2.6.27-rc5)
> [   78.815743] MSR: 00001032 <ME,IR,DR>  CR: 22242482  XER: 20000000
> [   78.821550] DAR: 0000004c, DSISR: 40000000
> [   78.827278] TASK = eef0df40[3035] 'mip6d' THREAD: eef18000
> [   78.827408] GPR00: 00001032 eef19b80 eef0df40 00000000 00008020 eef19c30 00000001 00000000
> [   78.833249] GPR08: eee5101c c05a5c10 ef9ad500 00000000 24242422 1005787c 00000000 1004f960
> [   78.839151] GPR16: 00000000 10024e90 10050040 48030018 0fe44150 00000000 00000000 eef19c30
> [   78.845046] GPR24: eef19e44 00000000 eef19bf8 efb37c14 eef19bf8 00008020 00009032 c0596064
> [   78.856671] NIP [c0097f54] kmem_cache_alloc+0x20/0x94
> [   78.862581] LR [c0334a28] dst_alloc+0x40/0xc4
> [   78.868451] Call Trace:
> [   78.874252] [eef19b80] [c03c1810] ip6_dst_lookup_tail+0x1c8/0x1dc (unreliable)
> [   78.880222] [eef19ba0] [c0334a28] dst_alloc+0x40/0xc4
> [   78.886164] [eef19bb0] [c03cd698] ip6_dst_blackhole+0x28/0x1cc
> [   78.892090] [eef19be0] [c03d9be8] rawv6_sendmsg+0x75c/0xc88
> [   78.897999] [eef19cb0] [c038bca4] inet_sendmsg+0x4c/0x78
> [   78.903907] [eef19cd0] [c03207c8] sock_sendmsg+0xac/0xe4
> [   78.909734] [eef19db0] [c03209e4] sys_sendmsg+0x1e4/0x2a0
> [   78.915540] [eef19f00] [c03220a8] sys_socketcall+0xfc/0x210
> [   78.921406] [eef19f40] [c0014b3c] ret_from_syscall+0x0/0x38
> [   78.927295] --- Exception: c01 at 0xfe2d730
> [   78.927297]     LR = 0xfe2d71c
> [   78.939019] Instruction dump:
> [   78.944835] 91640018 9144001c 900a0000 4bffff44 9421ffe0 7c0802a6 bf810010 7c9d2378
> [   78.950694] 90010024 7fc000a6 57c0045e 7c000124 <83e3004c> 8383005c 2f9f0000 419e0050
> [   78.956464] ---[ end trace 05fa1ed7972487a1 ]---
>
> Signed-off-by: Arnaud Ebalard <arno@...isbad.org>

Looks like I introduced this bug in commit
f2fc6a54585a1be6669613a31fbaba2ecbadcd36,
while adding network namespaces support to ipv6 routes.

Thanks for the fix.

Acked-by: Benjamin Thery <benjamin.thery@...l.net>

> ---
>  net/ipv6/route.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 776871e..f4385a6 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2708,6 +2708,8 @@ int __init ip6_route_init(void)
>        if (ret)
>                goto out_kmem_cache;
>
> +       ip6_dst_blackhole_ops.kmem_cachep = ip6_dst_ops_template.kmem_cachep;
> +
>        /* Registering of the loopback is done before this portion of code,
>         * the loopback reference in rt6_info will not be taken, do it
>         * manually for init_net */
> --
> 1.5.6.3
>
>
>
>
>
>
> --
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