On Wed, Nov 29, 2017 at 11:59 AM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote: > On Wed, 2017-11-29 at 09:34 -0800, Eric Dumazet wrote: >> On Wed, Nov 29, 2017 at 9:31 AM, Stephen Smalley <sds@xxxxxxxxxxxxx> >> wrote: >> > On Wed, 2017-11-29 at 21:26 +1100, James Morris wrote: >> > > I'm seeing a kernel stack corruption bug (detected via gcc) when >> > > running >> > > the SELinux testsuite on a 4.15-rc1 kernel, in the 2nd >> > > inet_socket >> > > test: >> > > >> > > https://github.com/SELinuxProject/selinux-testsuite/blob/master/t >> > > ests >> > > /inet_socket/test >> > > >> > > # Verify that unauthorized client cannot communicate with the >> > > server. >> > > $result = system >> > > "runcon -t test_inet_bad_client_t -- $basedir/client stream >> > > 127.0.0.1 65535 2>&1"; >> > > >> > > This correctlly causes an access control error in the Netlabel >> > > code, >> > > and >> > > the bug seems to be triggered during the ICMP send: >> > > >> > > [ 339.806024] SELinux: failure in selinux_parse_skb(), unable to >> > > parse packet >> > > [ 339.822505] Kernel panic - not syncing: stack-protector: >> > > Kernel >> > > stack is corrupted in: ffffffff81745af5 >> > > [ 339.822505] >> > > [ 339.852250] CPU: 4 PID: 3642 Comm: client Not tainted 4.15.0- >> > > rc1- >> > > test #15 >> > > [ 339.868498] Hardware name: LENOVO 10FGS0VA1L/30BC, BIOS >> > > FWKT68A 01/19/2017 >> > > [ 339.885060] Call Trace: >> > > [ 339.896875] <IRQ> >> > > [ 339.908103] dump_stack+0x63/0x87 >> > > [ 339.920645] panic+0xe8/0x248 >> > > [ 339.932668] ? ip_push_pending_frames+0x33/0x40 >> > > [ 339.946328] ? icmp_send+0x525/0x530 >> > > [ 339.958861] ? kfree_skbmem+0x60/0x70 >> > > [ 339.971431] __stack_chk_fail+0x1b/0x20 >> > > [ 339.984049] icmp_send+0x525/0x530 >> > > [ 339.996205] ? netlbl_skbuff_err+0x36/0x40 >> > > [ 340.008997] ? selinux_netlbl_err+0x11/0x20 >> > > [ 340.021816] ? selinux_socket_sock_rcv_skb+0x211/0x230 >> > > [ 340.035529] ? security_sock_rcv_skb+0x3b/0x50 >> > > [ 340.048471] ? sk_filter_trim_cap+0x44/0x1c0 >> > > [ 340.061246] ? tcp_v4_inbound_md5_hash+0x69/0x1b0 >> > > [ 340.074562] ? tcp_filter+0x2c/0x40 >> > > [ 340.086400] ? tcp_v4_rcv+0x820/0xa20 >> > > [ 340.098329] ? ip_local_deliver_finish+0x71/0x1a0 >> > > [ 340.111279] ? ip_local_deliver+0x6f/0xe0 >> > > [ 340.123535] ? ip_rcv_finish+0x3a0/0x3a0 >> > > [ 340.135523] ? ip_rcv_finish+0xdb/0x3a0 >> > > [ 340.147442] ? ip_rcv+0x27c/0x3c0 >> > > [ 340.158668] ? inet_del_offload+0x40/0x40 >> > > [ 340.170580] ? __netif_receive_skb_core+0x4ac/0x900 >> > > [ 340.183285] ? rcu_accelerate_cbs+0x5b/0x80 >> > > [ 340.195282] ? __netif_receive_skb+0x18/0x60 >> > > [ 340.207288] ? process_backlog+0x95/0x140 >> > > [ 340.218948] ? net_rx_action+0x26c/0x3b0 >> > > [ 340.230416] ? __do_softirq+0xc9/0x26a >> > > [ 340.241625] ? do_softirq_own_stack+0x2a/0x40 >> > > [ 340.253368] </IRQ> >> > > [ 340.262673] ? do_softirq+0x50/0x60 >> > > [ 340.273450] ? __local_bh_enable_ip+0x57/0x60 >> > > [ 340.285045] ? ip_finish_output2+0x175/0x350 >> > > [ 340.296403] ? ip_finish_output+0x127/0x1d0 >> > > [ 340.307665] ? nf_hook_slow+0x3c/0xb0 >> > > [ 340.318230] ? ip_output+0x72/0xe0 >> > > [ 340.328524] ? ip_fragment.constprop.54+0x80/0x80 >> > > [ 340.340070] ? ip_local_out+0x35/0x40 >> > > [ 340.350497] ? ip_queue_xmit+0x15c/0x3f0 >> > > [ 340.361060] ? __kmalloc_reserve.isra.40+0x31/0x90 >> > > [ 340.372484] ? __skb_clone+0x2e/0x130 >> > > [ 340.382633] ? tcp_transmit_skb+0x558/0xa10 >> > > [ 340.393262] ? tcp_connect+0x938/0xad0 >> > > [ 340.403370] ? ktime_get_with_offset+0x4c/0xb0 >> > > [ 340.414206] ? tcp_v4_connect+0x457/0x4e0 >> > > [ 340.424471] ? __inet_stream_connect+0xb3/0x300 >> > > [ 340.435195] ? inet_stream_connect+0x3b/0x60 >> > > [ 340.445607] ? SYSC_connect+0xd9/0x110 >> > > [ 340.455455] ? __audit_syscall_entry+0xaf/0x100 >> > > [ 340.466112] ? syscall_trace_enter+0x1d0/0x2b0 >> > > [ 340.476636] ? __audit_syscall_exit+0x209/0x290 >> > > [ 340.487151] ? SyS_connect+0xe/0x10 >> > > [ 340.496453] ? do_syscall_64+0x67/0x1b0 >> > > [ 340.506078] ? entry_SYSCALL64_slow_path+0x25/0x25 >> > > [ 340.516693] Kernel Offset: disabled >> > > [ 340.526393] Rebooting in 11 seconds.. >> > > >> > > This is mostly reliable, and I'm only seeing it on bare metal >> > > (not in >> > > a >> > > virtualbox vm). >> > > >> > > The SELinux skb parse error at the start only sometimes appears, >> > > and >> > > looking at the code, I suspect some kind of memory corruption >> > > being >> > > the >> > > cause at that point (basic packet header checks). >> > > >> > > I bisected the bug down to the following change: >> > > >> > > commit bffa72cf7f9df842f0016ba03586039296b4caaf >> > > Author: Eric Dumazet <edumazet@xxxxxxxxxx> >> > > Date: Tue Sep 19 05:14:24 2017 -0700 >> > > >> > > net: sk_buff rbnode reorg >> > > ... >> > > >> > > >> > > Anyone else able to reproduce this, or have any ideas on what's >> > > happening? >> > >> > So far I haven't been able to reproduce with 4.15-rc1 or -linus. >> > >> >> You might try adding KASAN in the picture ? ( CONFIG_KASAN=y ) > > Good idea: > > ================================================================== > BUG: > KASAN: stack-out-of-bounds in __ip_options_echo+0x430/0x5e0 > Write of > size 44 at addr ffff8803bc1c7560 by task ksoftirqd/1/16 > > CPU: 1 PID: 16 > Comm: ksoftirqd/1 Not tainted 4.15.0-rc1 #27 > Hardware name: Dell Inc. > Latitude E7470/0VNKRJ, BIOS 1.16.4 06/02/2017 > Call Trace: > > dump_stack+0x5c/0x7c > print_address_description+0x6a/0x280 > > kasan_report+0x254/0x370 > ? __ip_options_echo+0x430/0x5e0 > > memcpy+0x34/0x50 > __ip_options_echo+0x430/0x5e0 > icmp_send+0x48d/0x7a0 > > ? icmpv4_global_allow+0x50/0x50 > ? > selinux_netlbl_sk_security_reset+0x20/0x20 > ? avc_has_perm+0x238/0x260 > > ? avc_has_perm_noaudit+0x1d0/0x1d0 > ? selinux_peerlbl_enabled+0x50/0x50 > ? deref_stack_reg+0xd0/0xd0 > ? __save_stack_trace+0x82/0x100 > > selinux_socket_sock_rcv_skb+0x341/0x350 > ? > selinux_sock_rcv_skb_compat+0x200/0x200 > ? depot_save_stack+0x12f/0x460 > ? pskb_expand_head+0x9d/0x4d0 > ? save_stack+0x92/0xa0 > ? > kasan_kmalloc+0xa0/0xd0 > ? __kmalloc_node_track_caller+0xf5/0x290 > ? > skb_copy_and_csum_dev+0x142/0x180 > ? ip_rcv_finish+0x323/0x690 > ? > __netif_receive_skb_core+0xe16/0x13d0 > ? process_backlog+0x10a/0x280 > ? > net_rx_action+0x3ec/0x5a0 > ? __do_softirq+0x13f/0x36d > ? > __wake_up_common_lock+0xd7/0x130 > ? tcp_md5_do_lookup+0x27/0x240 > > security_sock_rcv_skb+0x47/0x60 > sk_filter_trim_cap+0x45/0x4b0 > ? > tcp4_proc_exit+0x11/0x11 > tcp_filter+0x5b/0x90 > > tcp_v4_rcv+0x108a/0x1360 > ip_local_deliver_finish+0xf7/0x300 > > ip_local_deliver+0xf2/0x1a0 > ? ip_call_ra_chain+0x220/0x220 > ? > ip_rcv_finish+0x690/0x690 > ? ip_rcv_finish+0x1b9/0x690 > > ip_rcv+0x4a6/0x660 > ? ip_local_deliver+0x1a0/0x1a0 > ? > inet_del_offload+0x40/0x40 > ? cpumask_next_and+0x4e/0x70 > ? > ip_local_deliver+0x1a0/0x1a0 > __netif_receive_skb_core+0xe16/0x13d0 > ? > netdev_info+0x100/0x100 > ? __accumulate_pelt_segments+0x47/0xd0 > ? > find_busiest_group+0x1100/0x1100 > ? > __update_load_avg_se.isra.31+0x34e/0x360 > ? > __update_load_avg_se.isra.31+0x201/0x360 > ? > __accumulate_pelt_segments+0x47/0xd0 > ? process_backlog+0x10a/0x280 > > process_backlog+0x10a/0x280 > net_rx_action+0x3ec/0x5a0 > ? > napi_complete_done+0x180/0x180 > ? __schedule+0x4e0/0xd50 > ? > sched_clock_cpu+0x14/0xe0 > __do_softirq+0x13f/0x36d > ? > takeover_tasklets+0x2b0/0x2b0 > run_ksoftirqd+0x25/0x40 > > smpboot_thread_fn+0x212/0x2b0 > ? sort_range+0x20/0x20 > ? > schedule+0x50/0xc0 > kthread+0x174/0x1c0 > ? sort_range+0x20/0x20 > ? > kthread_create_worker_on_cpu+0xc0/0xc0 > ret_from_fork+0x1f/0x30 > > The > buggy address belongs to the page: > page:ffffea000ef071c0 count:0 > mapcount:0 mapping: (null) index:0x0 > flags: 0x17ffffc0000000() > raw: 0017ffffc0000000 0000000000000000 0000000000000000 > 00000000ffffffff > raw: ffffea000ef071e0 ffffea000ef071e0 > 0000000000000000 0000000000000000 > page dumped because: kasan: bad > access detected > > Memory state around the buggy address: > > ffff8803bc1c7480: 00 00 00 f2 f2 f2 f2 00 00 00 00 00 00 00 f4 f2 > > ffff8803bc1c7500: f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 00 > >>ffff8803bc1c7580: 00 f4 f4 00 00 00 00 00 00 00 00 00 00 00 00 00 > > ^ > ffff8803bc1c7600: 00 00 f1 f1 f1 f1 04 f4 f4 f4 f2 > f2 f2 f2 00 f4 > ffff8803bc1c7680: f4 f4 f2 f2 f2 f2 00 00 00 00 f2 f2 > f2 f2 00 00 > > ================================================================== > > Disabling lock debugging due to kernel taint > SELinux: failure in > selinux_parse_skb(), unable to parse packet I suspect this exposes an ancient bug, caused by fact that TCP moves IP[6]CB in skb->cb[] Basically the 2nd tcp_filter() added in commit 8fac365f63c866a00015fa13932d8ffc584518b8 ("tcp: Add a tcp_filter hook before handle ack packet") was not expecting selinux code being called a 2nd time, while skb->cb[] has been mangled [1] [1] memmove(&TCP_SKB_CB(skb)->header.h4, IPCB(skb), sizeof(struct inet_skb_parm));
