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Message-ID: <b8947e4ef24c00cd9757b408bece1b8c25f7002c.camel@kernel.org>
Date: Tue, 12 Nov 2024 09:28:47 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Liu Jian <liujian56@...wei.com>, chuck.lever@...cle.com, neilb@...e.de,
okorniev@...hat.com, Dai.Ngo@...cle.com, tom@...pey.com,
trondmy@...nel.org, anna@...nel.org, davem@...emloft.net,
edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
ebiederm@...ssion.com, kuniyu@...zon.com
Cc: linux-nfs@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net v4] sunrpc: fix one UAF issue caused by sunrpc
kernel tcp socket
On Tue, 2024-11-12 at 21:54 +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.
>
> To fix this problem, let's hold netns refcnt for the tcp kernel socket as
> done in other modules. This is an ugly hack which can easily be backported
> to earlier kernels. A proper fix which cleans up the interfaces will
> follow, but may not be so easy to backport.
>
> Fixes: 26abe14379f8 ("net: Modify sk_alloc to not reference count the netns of kernel sockets.")
> Signed-off-by: Liu Jian <liujian56@...wei.com>
> ---
> v3->v4: Add the commit message suggested by NeilBrown.
> net/sunrpc/svcsock.c | 4 ++++
> net/sunrpc/xprtsock.c | 7 +++++++
> 2 files changed, 11 insertions(+)
>
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index 6f272013fd9b..d4330aaadc23 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -1551,6 +1551,10 @@ static struct svc_xprt *svc_create_socket(struct svc_serv *serv,
> newlen = error;
>
> if (protocol == IPPROTO_TCP) {
> + __netns_tracker_free(net, &sock->sk->ns_tracker, false);
> + sock->sk->sk_net_refcnt = 1;
> + get_net_track(net, &sock->sk->ns_tracker, GFP_KERNEL);
> + sock_inuse_add(net, 1);
> if ((error = kernel_listen(sock, 64)) < 0)
> goto bummer;
> }
Given that this is an ugly hack, some comments over these new blocks
that explains exactly what is going on would be welcome. That might
make it simpler to review the eventual change to a cleaner interface
later too.
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index d2f31b59457b..906a1b563aee 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -1942,6 +1942,13 @@ static struct socket *xs_create_sock(struct rpc_xprt *xprt,
> goto out;
> }
>
> + if (protocol == IPPROTO_TCP) {
> + __netns_tracker_free(xprt->xprt_net, &sock->sk->ns_tracker, false);
> + sock->sk->sk_net_refcnt = 1;
> + get_net_track(xprt->xprt_net, &sock->sk->ns_tracker, GFP_KERNEL);
> + sock_inuse_add(xprt->xprt_net, 1);
> + }
> +
> filp = sock_alloc_file(sock, O_NONBLOCK, NULL);
> if (IS_ERR(filp))
> return ERR_CAST(filp);
Acked-by: Jeff Layton <jlayton@...nel.org>
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