linux-kernel - Re: [kmemcheck] WARNING: kmemcheck: Caught 32-bit read from uninitialized memory, in sock_init

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Date:	Wed, 26 Aug 2009 09:13:31 +0200
From:	Vegard Nossum <vegard.nossum@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Pekka Enberg <penberg@...helsinki.fi>, linux-kernel@...r.kernel.org
Subject: Re: [kmemcheck] WARNING: kmemcheck: Caught 32-bit read from 
	uninitialized memory, in sock_init_data()

2009/8/26 Ingo Molnar <mingo@...e.hu>:
>
> -tip testing found another kmemcheck warning:
>
> calling  netlink_proto_init+0x0/0x1b0 @ 1
> NET: Registered protocol family 16
> initcall netlink_proto_init+0x0/0x1b0 returned 0 after 39062 usecs
> calling  olpc_init+0x0/0x110 @ 1
> WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (f5c38304)
> 0100000002000000000000000000000000000000ad4eaddeffffffffffffffff
>  i i i i i i u u i i i i i i i i i i i i i i i i i i i i i i i i
>         ^
>
> Pid: 1, comm: swapper Not tainted (2.6.31-rc7-tip-01170-gaaea9cf-dirty #24) P4DC6
> EIP: 0060:[<c15c8ab1>] EFLAGS: 00010286 CPU: 0
> EIP is at sock_init_data+0xe1/0x220
> EAX: 0001b000 EBX: f606196c ECX: 00000000 EDX: c1a148d2
> ESI: f6061800 EDI: f5c38300 EBP: f606ef0c ESP: c1ceb9ac
>  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
> CR0: 8005003b CR2: f60a8108 CR3: 01a61000 CR4: 000006f0
> DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> DR6: ffff4ff0 DR7: 00000400
>  [<c15fac15>] __netlink_create+0x35/0xa0
>  [<c15fd01a>] netlink_kernel_create+0x5a/0x180
>  [<c15df55e>] rtnetlink_net_init+0x1e/0x50
>  [<c15d130a>] register_pernet_operations+0x6a/0xf0
>  [<c15d14fe>] register_pernet_subsys+0x1e/0x30
>  [<c1b3d84c>] rtnetlink_init+0x4c/0x100
>  [<c1b3e105>] netlink_proto_init+0x105/0x1b0
>  [<c1001037>] do_one_initcall+0x27/0x170
>  [<c1afea97>] kernel_init+0x157/0x210
>  [<c10039a7>] kernel_thread_helper+0x7/0x10
>  [<ffffffff>] 0xffffffff
> initcall olpc_init+0x0/0x110 returned 0 after 0 usecs
> calling  bdi_class_init+0x0/0x40 @ 1
>
> config attached.

Thanks. AFAICT, it's this one:

1816 void sock_init_data(struct socket *sock, struct sock *sk)
1817 {
...
1835         sock_set_flag(sk, SOCK_ZAPPED);

Which sort of makes sense, given all the trouble we've had with bitfields/flags.

Is it possible that struct sock's sk_flags is (partially)
uninitialized at this point?

I'll investigate more later, lecture of statistics is about to begin.


Vegard
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