From: Ziyang Xuan william.xuanziyang@huawei.com

We get a bug during ltp can_filter test as following.

=========================================== [60919.264984] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 [60919.265223] PGD 8000003dda726067 P4D 8000003dda726067 PUD 3dda727067 PMD 0 [60919.265443] Oops: 0000 [#1] SMP PTI [60919.265550] CPU: 30 PID: 3638365 Comm: can_filter Kdump: loaded Tainted: G W 4.19.90+ #1 [60919.266068] RIP: 0010:selinux_socket_sock_rcv_skb+0x3e/0x200 [60919.293289] RSP: 0018:ffff8d53bfc03cf8 EFLAGS: 00010246 [60919.307140] RAX: 0000000000000000 RBX: 000000000000001d RCX: 0000000000000007 [60919.320756] RDX: 0000000000000001 RSI: ffff8d5104a8ed00 RDI: ffff8d53bfc03d30 [60919.334319] RBP: ffff8d9338056800 R08: ffff8d53bfc29d80 R09: 0000000000000001 [60919.347969] R10: ffff8d53bfc03ec0 R11: ffffb8526ef47c98 R12: ffff8d53bfc03d30 [60919.350320] perf: interrupt took too long (3063 > 2500), lowering kernel.perf_event_max_sample_rate to 65000 [60919.361148] R13: 0000000000000001 R14: ffff8d53bcf90000 R15: 0000000000000000 [60919.361151] FS: 00007fb78b6b3600(0000) GS:ffff8d53bfc00000(0000) knlGS:0000000000000000 [60919.400812] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [60919.413730] CR2: 0000000000000010 CR3: 0000003e3f784006 CR4: 00000000007606e0 [60919.426479] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [60919.439339] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [60919.451608] PKRU: 55555554 [60919.463622] Call Trace: [60919.475617] <IRQ> [60919.487122] ? update_load_avg+0x89/0x5d0 [60919.498478] ? update_load_avg+0x89/0x5d0 [60919.509822] ? account_entity_enqueue+0xc5/0xf0 [60919.520709] security_sock_rcv_skb+0x2a/0x40 [60919.531413] sk_filter_trim_cap+0x47/0x1b0 [60919.542178] ? kmem_cache_alloc+0x38/0x1b0 [60919.552444] sock_queue_rcv_skb+0x17/0x30 [60919.562477] raw_rcv+0x110/0x190 [can_raw] [60919.572539] can_rcv_filter+0xbc/0x1b0 [can] [60919.582173] can_receive+0x6b/0xb0 [can] [60919.591595] can_rcv+0x31/0x70 [can] [60919.600783] __netif_receive_skb_one_core+0x5a/0x80 [60919.609864] process_backlog+0x9b/0x150 [60919.618691] net_rx_action+0x156/0x400 [60919.627310] ? sched_clock_cpu+0xc/0xa0 [60919.635714] __do_softirq+0xe8/0x2e9 [60919.644161] do_softirq_own_stack+0x2a/0x40 [60919.652154] </IRQ> [60919.659899] do_softirq.part.17+0x4f/0x60 [60919.667475] __local_bh_enable_ip+0x60/0x70 [60919.675089] __dev_queue_xmit+0x539/0x920 [60919.682267] ? finish_wait+0x80/0x80 [60919.689218] ? finish_wait+0x80/0x80 [60919.695886] ? sock_alloc_send_pskb+0x211/0x230 [60919.702395] ? can_send+0xe5/0x1f0 [can] [60919.708882] can_send+0xe5/0x1f0 [can] [60919.715037] raw_sendmsg+0x16d/0x268 [can_raw]

It's because raw_setsockopt() concurrently with unregister_netdevice_many(). Concurrent scenario as following.

cpu0 cpu1 raw_bind raw_setsockopt unregister_netdevice_many unlist_netdevice dev_get_by_index raw_notifier raw_enable_filters ...... can_rx_register can_rcv_list_find(..., net->can.rx_alldev_list)

......

sock_close raw_release(sock_a)

......

can_receive can_rcv_filter(net->can.rx_alldev_list, ...) raw_rcv(skb, sock_a) BUG

After unlist_netdevice(), dev_get_by_index() return NULL in raw_setsockopt(). Function raw_enable_filters() will add sock and can_filter to net->can.rx_alldev_list. Then the sock is closed. Followed by, we sock_sendmsg() to a new vcan device use the same can_filter. Protocol stack match the old receiver whose sock has been released on net->can.rx_alldev_list in can_rcv_filter(). Function raw_rcv() uses the freed sock. UAF BUG is triggered.

We can find that the key issue is that net_device has not been protected in raw_setsockopt(). Use rtnl_lock to protect net_device in raw_setsockopt().

Fixes: c18ce101f2e4 ("[CAN]: Add raw protocol") Link: https://lore.kernel.org/r/20210722070819.1048263-1-william.xuanziyang@huawei... Cc: linux-stable stable@vger.kernel.org Signed-off-by: Ziyang Xuan william.xuanziyang@huawei.com Acked-by: Oliver Hartkopp socketcan@hartkopp.net Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de --- net/can/raw.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/net/can/raw.c b/net/can/raw.c index ed4fcb7ab0c3..cd5a49380116 100644 --- a/net/can/raw.c +++ b/net/can/raw.c @@ -546,10 +546,18 @@ static int raw_setsockopt(struct socket *sock, int level, int optname, return -EFAULT; }

+ rtnl_lock(); lock_sock(sk);

- if (ro->bound && ro->ifindex) + if (ro->bound && ro->ifindex) { dev = dev_get_by_index(sock_net(sk), ro->ifindex); + if (!dev) { + if (count > 1) + kfree(filter); + err = -ENODEV; + goto out_fil; + } + }

if (ro->bound) { /* (try to) register the new filters */ @@ -588,6 +596,7 @@ static int raw_setsockopt(struct socket *sock, int level, int optname, dev_put(dev);

release_sock(sk); + rtnl_unlock();

break;

@@ -600,10 +609,16 @@ static int raw_setsockopt(struct socket *sock, int level, int optname,

err_mask &= CAN_ERR_MASK;

+ rtnl_lock(); lock_sock(sk);

- if (ro->bound && ro->ifindex) + if (ro->bound && ro->ifindex) { dev = dev_get_by_index(sock_net(sk), ro->ifindex); + if (!dev) { + err = -ENODEV; + goto out_err; + } + }

/* remove current error mask */ if (ro->bound) { @@ -627,6 +642,7 @@ static int raw_setsockopt(struct socket *sock, int level, int optname, dev_put(dev);

release_sock(sk); + rtnl_unlock();

break;