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Message-ID: <65b652e60d8681b0898efcd6e020f69447b6e606.camel@hammerspace.com>
Date: Thu, 24 Oct 2024 02:20:35 +0000
From: Trond Myklebust <trondmy@...merspace.com>
To: "Dai.Ngo@...cle.com" <Dai.Ngo@...cle.com>, "davem@...emloft.net"
<davem@...emloft.net>, "chuck.lever@...cle.com" <chuck.lever@...cle.com>,
"ebiederm@...ssion.com" <ebiederm@...ssion.com>, "okorniev@...hat.com"
<okorniev@...hat.com>, "anna@...nel.org" <anna@...nel.org>, "kuba@...nel.org"
<kuba@...nel.org>, "tom@...pey.com" <tom@...pey.com>, "jlayton@...nel.org"
<jlayton@...nel.org>, "liujian56@...wei.com" <liujian56@...wei.com>,
"neilb@...e.de" <neilb@...e.de>, "edumazet@...gle.com" <edumazet@...gle.com>,
"pabeni@...hat.com" <pabeni@...hat.com>
CC: "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net] sunrpc: fix one UAF issue caused by sunrpc kernel tcp
socket
On Thu, 2024-10-24 at 09:55 +0800, Liu Jian wrote:
> BUG: KASAN: slab-use-after-free in
> tcp_write_timer_handler+0x156/0x3e0
> Read of size 1 at addr ffff888111f322cd by task swapper/0/0
>
> CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.12.0-rc4-dirty #7
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1
> Call Trace:
> <IRQ>
> dump_stack_lvl+0x68/0xa0
> print_address_description.constprop.0+0x2c/0x3d0
> print_report+0xb4/0x270
> kasan_report+0xbd/0xf0
> tcp_write_timer_handler+0x156/0x3e0
> tcp_write_timer+0x66/0x170
> call_timer_fn+0xfb/0x1d0
> __run_timers+0x3f8/0x480
> run_timer_softirq+0x9b/0x100
> handle_softirqs+0x153/0x390
> __irq_exit_rcu+0x103/0x120
> irq_exit_rcu+0xe/0x20
> sysvec_apic_timer_interrupt+0x76/0x90
> </IRQ>
> <TASK>
> asm_sysvec_apic_timer_interrupt+0x1a/0x20
> RIP: 0010:default_idle+0xf/0x20
> Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90
> 90 90
> 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 33 f8 25 00 fb f4 <fa> c3 cc
> cc cc
> cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
> RSP: 0018:ffffffffa2007e28 EFLAGS: 00000242
> RAX: 00000000000f3b31 RBX: 1ffffffff4400fc7 RCX: ffffffffa09c3196
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff9f00590f
> RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed102360835d
> R10: ffff88811b041aeb R11: 0000000000000001 R12: 0000000000000000
> R13: ffffffffa202d7c0 R14: 0000000000000000 R15: 00000000000147d0
> default_idle_call+0x6b/0xa0
> cpuidle_idle_call+0x1af/0x1f0
> do_idle+0xbc/0x130
> cpu_startup_entry+0x33/0x40
> rest_init+0x11f/0x210
> start_kernel+0x39a/0x420
> x86_64_start_reservations+0x18/0x30
> x86_64_start_kernel+0x97/0xa0
> common_startup_64+0x13e/0x141
> </TASK>
>
> Allocated by task 595:
> kasan_save_stack+0x24/0x50
> kasan_save_track+0x14/0x30
> __kasan_slab_alloc+0x87/0x90
> kmem_cache_alloc_noprof+0x12b/0x3f0
> copy_net_ns+0x94/0x380
> create_new_namespaces+0x24c/0x500
> unshare_nsproxy_namespaces+0x75/0xf0
> ksys_unshare+0x24e/0x4f0
> __x64_sys_unshare+0x1f/0x30
> do_syscall_64+0x70/0x180
> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> Freed by task 100:
> kasan_save_stack+0x24/0x50
> kasan_save_track+0x14/0x30
> kasan_save_free_info+0x3b/0x60
> __kasan_slab_free+0x54/0x70
> kmem_cache_free+0x156/0x5d0
> cleanup_net+0x5d3/0x670
> process_one_work+0x776/0xa90
> worker_thread+0x2e2/0x560
> kthread+0x1a8/0x1f0
> ret_from_fork+0x34/0x60
> ret_from_fork_asm+0x1a/0x30
>
> Reproduction script:
>
> mkdir -p /mnt/nfsshare
> mkdir -p /mnt/nfs/netns_1
> mkfs.ext4 /dev/sdb
> mount /dev/sdb /mnt/nfsshare
> systemctl restart nfs-server
> chmod 777 /mnt/nfsshare
> exportfs -i -o rw,no_root_squash *:/mnt/nfsshare
>
> ip netns add netns_1
> ip link add name veth_1_peer type veth peer veth_1
> ifconfig veth_1_peer 11.11.0.254 up
> ip link set veth_1 netns netns_1
> ip netns exec netns_1 ifconfig veth_1 11.11.0.1
>
> ip netns exec netns_1 /root/iptables -A OUTPUT -d 11.11.0.254 -p tcp
> \
> --tcp-flags FIN FIN -j DROP
>
> (note: In my environment, a DESTROY_CLIENTID operation is always sent
> immediately, breaking the nfs tcp connection.)
> ip netns exec netns_1 timeout -s 9 300 mount -t nfs -o
> proto=tcp,vers=4.1 \
> 11.11.0.254:/mnt/nfsshare /mnt/nfs/netns_1
>
> ip netns del netns_1
>
> The reason here is that the tcp socket in netns_1 (nfs side) has been
> shutdown and closed (done in xs_destroy), but the FIN message (with
> ack)
> is discarded, and the nfsd side keeps sending retransmission
> messages.
> As a result, when the tcp sock in netns_1 processes the received
> message,
> it sends the message (FIN message) in the sending queue, and the tcp
> timer
> is re-established. When the network namespace is deleted, the net
> structure
> accessed by tcp's timer handler function causes problems.
>
> The modification here aborts the TCP connection directly in
> xs_destroy().
>
> Fixes: 26abe14379f8 ("net: Modify sk_alloc to not reference count the
> netns of kernel sockets.")
> Signed-off-by: Liu Jian <liujian56@...wei.com>
> ---
> net/sunrpc/xprtsock.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index 0e1691316f42..91ee3484155a 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -1287,6 +1287,9 @@ static void xs_reset_transport(struct sock_xprt
> *transport)
> release_sock(sk);
> mutex_unlock(&transport->recv_mutex);
>
> + if (sk->sk_prot == &tcp_prot)
> + tcp_abort(sk, ECONNABORTED);
We've already called kernel_sock_shutdown(sock, SHUT_RDWR), and we're
about to close the socket. Why on earth should we need a hack like the
above in order to abort the connection at this point?
This would appear to be a networking layer bug, and not an RPC level
problem.
> +
> trace_rpc_socket_close(xprt, sock);
> __fput_sync(filp);
>
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@...merspace.com
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