netdev - Re: [PATCH ipsec v2] xfrm: policy: fix metadata dst->dev xmit null pointer dereference

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Message-ID: <20220818111103.GG566407@gauss3.secunet.de>
Date:   Thu, 18 Aug 2022 13:11:03 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     Nikolay Aleksandrov <razor@...ckwall.org>
CC:     <netdev@...r.kernel.org>, <davem@...emloft.net>,
        <edumazet@...gle.com>, <pabeni@...hat.com>, <kuba@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH ipsec v2] xfrm: policy: fix metadata dst->dev xmit null
 pointer dereference

On Tue, Aug 16, 2022 at 06:30:50PM +0300, Nikolay Aleksandrov wrote:
> When we try to transmit an skb with metadata_dst attached (i.e. dst->dev
> == NULL) through xfrm interface we can hit a null pointer dereference[1]
> in xfrmi_xmit2() -> xfrm_lookup_with_ifid() due to the check for a
> loopback skb device when there's no policy which dereferences dst->dev
> unconditionally. Not having dst->dev can be interepreted as it not being
> a loopback device, so just add a check for a null dst_orig->dev.
> 
> With this fix xfrm interface's Tx error counters go up as usual.
> 
> [1] net-next calltrace captured via netconsole:
>   BUG: kernel NULL pointer dereference, address: 00000000000000c0
>   #PF: supervisor read access in kernel mode
>   #PF: error_code(0x0000) - not-present page
>   PGD 0 P4D 0
>   Oops: 0000 [#1] PREEMPT SMP
>   CPU: 1 PID: 7231 Comm: ping Kdump: loaded Not tainted 5.19.0+ #24
>   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-1.fc36 04/01/2014
>   RIP: 0010:xfrm_lookup_with_ifid+0x5eb/0xa60
>   Code: 8d 74 24 38 e8 26 a4 37 00 48 89 c1 e9 12 fc ff ff 49 63 ed 41 83 fd be 0f 85 be 01 00 00 41 be ff ff ff ff 45 31 ed 48 8b 03 <f6> 80 c0 00 00 00 08 75 0f 41 80 bc 24 19 0d 00 00 01 0f 84 1e 02
>   RSP: 0018:ffffb0db82c679f0 EFLAGS: 00010246
>   RAX: 0000000000000000 RBX: ffffd0db7fcad430 RCX: ffffb0db82c67a10
>   RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffb0db82c67a80
>   RBP: ffffb0db82c67a80 R08: ffffb0db82c67a14 R09: 0000000000000000
>   R10: 0000000000000000 R11: ffff8fa449667dc8 R12: ffffffff966db880
>   R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000000
>   FS:  00007ff35c83f000(0000) GS:ffff8fa478480000(0000) knlGS:0000000000000000
>   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>   CR2: 00000000000000c0 CR3: 000000001ebb7000 CR4: 0000000000350ee0
>   Call Trace:
>    <TASK>
>    xfrmi_xmit+0xde/0x460
>    ? tcf_bpf_act+0x13d/0x2a0
>    dev_hard_start_xmit+0x72/0x1e0
>    __dev_queue_xmit+0x251/0xd30
>    ip_finish_output2+0x140/0x550
>    ip_push_pending_frames+0x56/0x80
>    raw_sendmsg+0x663/0x10a0
>    ? try_charge_memcg+0x3fd/0x7a0
>    ? __mod_memcg_lruvec_state+0x93/0x110
>    ? sock_sendmsg+0x30/0x40
>    sock_sendmsg+0x30/0x40
>    __sys_sendto+0xeb/0x130
>    ? handle_mm_fault+0xae/0x280
>    ? do_user_addr_fault+0x1e7/0x680
>    ? kvm_read_and_reset_apf_flags+0x3b/0x50
>    __x64_sys_sendto+0x20/0x30
>    do_syscall_64+0x34/0x80
>    entry_SYSCALL_64_after_hwframe+0x46/0xb0
>   RIP: 0033:0x7ff35cac1366
>   Code: eb 0b 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 72 c3 90 55 48 83 ec 30 44 89 4c 24 2c 4c 89
>   RSP: 002b:00007fff738e4028 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
>   RAX: ffffffffffffffda RBX: 00007fff738e57b0 RCX: 00007ff35cac1366
>   RDX: 0000000000000040 RSI: 0000557164e4b450 RDI: 0000000000000003
>   RBP: 0000557164e4b450 R08: 00007fff738e7a2c R09: 0000000000000010
>   R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000040
>   R13: 00007fff738e5770 R14: 00007fff738e4030 R15: 0000001d00000001
>    </TASK>
>   Modules linked in: netconsole veth br_netfilter bridge bonding virtio_net [last unloaded: netconsole]
>   CR2: 00000000000000c0
> 
> CC: Steffen Klassert <steffen.klassert@...unet.com>
> CC: Daniel Borkmann <daniel@...earbox.net>
> Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy")
> Signed-off-by: Nikolay Aleksandrov <razor@...ckwall.org>

Applied, thanks Nikolay!