linux-kernel - Re: [PATCH] inet: sanitize socket() protocol value

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Date:	Wed, 16 Dec 2015 17:01:51 -0800
From:	Eric Dumazet <edumazet@...gle.com>
To:	Vegard Nossum <vegard.nossum@...cle.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] inet: sanitize socket() protocol value

On Wed, Dec 16, 2015 at 4:57 PM, Vegard Nossum <vegard.nossum@...cle.com> wrote:
> If you create a raw socket with a protocol of e.g. 0x10000, then
> inet_sk(sk)->inet_num will get set to 0 since it only has room for 16
> bits. This causes problems further down the line as lots of code makes
> assumptions about ->inet_num, for example connect()...inet_autobind()
> will attempt to call sk->sk_prot->get_port() which is invalid:
>
>   BUG: unable to handle kernel NULL pointer dereference at           (null)
>   IP: [<          (null)>]           (null)
>   PGD 19ea0067 PUD 19d3f067 PMD 0
>   Oops: 0010 [#1] SMP
>   CPU: 1 PID: 849 Comm: a.out Not tainted 4.4.0-rc4+ #287
>   task: ffff880019a12640 ti: ffff88000008c000 task.ti: ffff88000008c000
>   RIP: 0010:[<0000000000000000>]  [<          (null)>]           (null)
>   RSP: 0018:ffff88000008fe50  EFLAGS: 00010246
>   RAX: ffffffff81cc61f0 RBX: ffff880019d2ca80 RCX: 0000000000000802
>   RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff880019d2ca80
>   RBP: ffff88000008fe60 R08: 00007f0e6b132e80 R09: ffff880019d2ca80
>   R10: ffff88001a7a72e0 R11: ffff880019a12640 R12: 000000000000000b
>   R13: 0000000000400644 R14: 0000000000000000 R15: 0000000000000000
>   FS:  00007f0e6b355740(0000) GS:ffff88001a900000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 0000000000000000 CR3: 0000000019d3d000 CR4: 00000000001406a0
>   Stack:
>    ffffffff815f1c69 ffff880019d2ca80 ffff88000008fe88 ffffffff815f1cde
>    0000000b0000000b ffff88000008fea0 ffff880019484000 ffff88000008ff38
>    ffffffff8156f310 0000000000000000 2a2a2a2a2a2a2a2a ffffffff8100002a
>   Call Trace:
>    [<ffffffff815f1c69>] ? inet_autobind+0x23/0x50
>    [<ffffffff815f1cde>] inet_dgram_connect+0x48/0x64
>    [<ffffffff8156f310>] SYSC_connect+0x84/0xae
>    [<ffffffff8156f3ed>] ? sock_alloc_file+0xb3/0x108
>    [<ffffffff81132021>] ? fd_install+0x20/0x22
>    [<ffffffff815700d2>] ? SYSC_socket+0x62/0x90
>    [<ffffffff81570318>] SyS_connect+0x9/0xb
>    [<ffffffff816fb86e>] entry_SYSCALL_64_fastpath+0x12/0x71
>   Code:  Bad RIP value.
>   RIP  [<          (null)>]           (null)
>    RSP <ffff88000008fe50>
>   CR2: 0000000000000000
>   ---[ end trace bd60b4fe2edc2537 ]---
>
> Signed-off-by: Vegard Nossum <vegard.nossum@...cle.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: <stable@...r.kernel.org>
> ---
>  net/ipv4/af_inet.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git net/ipv4/af_inet.c net/ipv4/af_inet.c
> index 11c4ca1..4e1583a 100644
> --- net/ipv4/af_inet.c
> +++ net/ipv4/af_inet.c
> @@ -316,6 +316,12 @@ lookup_protocol:
>
>         WARN_ON(!answer_prot->slab);
>
> +       /* Check that the protocol we were given will actually fit in
> +        * inet->inet_num. */
> +       err = -EINVAL;
> +       if (protocol != (typeof(inet->inet_num)) protocol)
> +               goto out;
> +
>         err = -ENOBUFS;
>         sk = sk_alloc(net, PF_INET, GFP_KERNEL, answer_prot, kern);
>         if (!sk)
> --
> 1.9.1
>

It looks already fixed in a better way (IPv6, ...)

http://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=79462ad02e861803b3840cc782248c7359451cd9

Thanks
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