Re: Kernel 4.19.47 with commit 8715ce033eb37f539e73b1570bf56404b21d46cd failed to execute NX-protected page

[Sasha Levin <sashal@kernel.org>]

On Wed, Jun 05, 2019 at 03:04:26PM +0100, Daniel Dao wrote:
>Hi there,
>
>We are testing kernel 4.19.47 with some tools utilizing kprobe,
>resulting in panics that look like:
>
>[ 1085.318031] kernel tried to execute NX-protected page - exploit
>attempt? (uid: 65534)
>[ 1085.334028] BUG: unable to handle kernel paging request at ffffffffc0428000
>[ 1085.349128] PGD 13a3e10067 P4D 13a3e10067 PUD 13a3e12067 PMD
>c1e860067 PTE 8000000bbd075061
>[ 1085.365779] Oops: 0011 [#1] SMP KASAN PTI
>[ 1085.377879] CPU: 30 PID: 29734 Comm: nginx-fl Tainted: G    B
>O      4.19.47-cloudflare-kasan-2019.6.0 #2019.6.0
>[ 1085.396652] Hardware name: Quanta Computer Inc QuantaPlex
>T41S-2U/S2S-MB, BIOS S2S_3B10.03 06/21/2018
>[ 1085.414041] RIP: 0010:0xffffffffc0428000
>[ 1085.425965] Code: Bad RIP value.
>[ 1085.436832] RSP: 0018:ffff88a015e2fb18 EFLAGS: 00010246
>[ 1085.449853] RAX: 0000000000000003 RBX: ffff889f73448900 RCX: 0000000000000218
>[ 1085.464719] RDX: ffff889fe4893c00 RSI: 0000000000000002 RDI: ffff889f73448900
>[ 1085.479626] RBP: ffff88a015e2fe18 R08: 0000000000000006 R09: 0000000000000000
>[ 1085.494677] R10: 000000008a08850a R11: 0000000000000000 R12: ffff889f7344890c
>[ 1085.509890] R13: ffff889f73448c54 R14: ffff889f73448c7a R15: 0000000000002c19
>[ 1085.525252] FS:  00007f51582f5680(0000) GS:ffff88a03fb80000(0000)
>knlGS:0000000000000000
>[ 1085.541810] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>[ 1085.555812] CR2: ffffffffc0427fd6 CR3: 0000002039fee004 CR4: 00000000001606e0
>[ 1085.571154] Call Trace:
>[ 1085.581676]  ? tcp_set_state+0x5/0x5b0
>[ 1085.593532]  ? tcp_v4_connect+0xbd7/0x2000
>[ 1085.605809]  ? tcp_sk_init+0x1220/0x1220
>[ 1085.617810]  ? selinux_socket_connect_helper.isra.55+0x277/0x400
>[ 1085.631808]  ? sock_poll+0x218/0x300
>[ 1085.643407]  ? selinux_netcache_avc_callback+0x30/0x30
>[ 1085.656701]  ? __inet_stream_connect+0x630/0xbd0
>[ 1085.669508]  ? expand_files.part.9+0x640/0x640
>[ 1085.682145]  ? ipip_gro_complete+0x110/0x110
>[ 1085.694627]  ? __inet_stream_connect+0xbd0/0xbd0
>[ 1085.707397]  ? inet_stream_connect+0x53/0xa0
>[ 1085.719830]  ? __sys_connect+0x1f6/0x270
>[ 1085.731964]  ? __ia32_sys_accept+0xb0/0xb0
>[ 1085.744201]  ? mutex_lock+0x85/0xe0
>[ 1085.755815]  ? ep_show_fdinfo+0x3c0/0x3c0
>[ 1085.767916]  ? syscall_trace_enter+0x566/0xc30
>[ 1085.780429]  ? __x64_sys_epoll_ctl+0x237/0x1080
>[ 1085.792883]  ? exit_to_usermode_loop+0x140/0x140
>[ 1085.805425]  ? __audit_syscall_exit+0x73e/0xa30
>[ 1085.817925]  ? __x64_sys_connect+0x6f/0xb0
>[ 1085.829915]  ? do_syscall_64+0x8e/0x280
>[ 1085.841539]  ? prepare_exit_to_usermode+0xe1/0x140
>[ 1085.854067]  ? entry_SYSCALL_64_after_hwframe+0x44/0xa9
>[ 1085.867000] Modules linked in: xt_length xt_connlimit nf_conncount
>xt_hashlimit iptable_security sch_fq md_mod dm_crypt algif_skcipher
>af_alg dm_mod dax ip6table_nat nf_nat_ipv6 ip6table_mangle
>ip6table_security ip6table_raw xt_nat iptable_nat nf_nat_ipv4 nf_nat
>xt_TPROXY nf_tproxy_ipv6 nf_tproxy_ipv4 xt_connmark iptable_mangle
>xt_owner ip6table_filter ip6_tables xt_CT xt_socket nf_socket_ipv4
>nf_socket_ipv6 iptable_raw nfnetlink_log xt_NFLOG xt_bpf xt_comment
>xt_conntrack xt_mark xt_multiport xt_set xt_tcpudp ipt_GLBREDIRECT(O)
>nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 fou ip6_udp_tunnel
>udp_tunnel iptable_filter bpfilter ip_set_hash_netport ip_set_hash_net
>ip_set_hash_ip ip_set nfnetlink sit ipip tunnel4 ip_tunnel tun 8021q
>garp stp mrp llc sb_edac x86_pkg_temp_thermal kvm_intel kvm irqbypass
>[ 1085.996378]  crc32_pclmul crc32c_intel pcbc aesni_intel aes_x86_64
>ipmi_ssif crypto_simd cryptd glue_helper intel_cstate intel_uncore
>sfc(O) intel_rapl_perf tpm_tis tpm_tis_core mdio tpm ipmi_si
>ipmi_devintf ipmi_msghandler efivarfs ip_tables x_tables
>
>Reproducible steps on my local machine are as follow:
>1. Run kernel 4.19.47
>2. We are going to test kprobe on tcp_set_state using
>https://github.com/iovisor/bcc/blob/master/tools/tcplife.py. But
>probably any workload utilizing kprobe would work
>    - Run some workload that creating tcp connections. I'm runing
>`python -m SimpleHTTPServer` and `wrk -d60s -c10
>http://localhost:8000`
>    - Run the script
>https://github.com/iovisor/bcc/blob/master/tools/tcplife.py. Expect it
>to not crash the kernel and producing some output
>
>Reverting commit 8715ce033eb37f539e73b1570bf56404b21d46cd makes it
>work for me locally. I also tested kernel
>5.2.0-rc3-00024-g788a024921c4 locally (latest Linus tree) and not
>seeing the issue, so maybe somewhere along the backporting process, we
>failed to backport all the required patches ?

Uh, that might indeed be the case. Could you try cherry picking the
following 3 patches on top of your 4.19 tree and trying again?

git cherry-pick d2a68c4effd821f0871d20368f76b609349c8a3b 3c0dab44e22782359a0a706cbce72de99a22aa75 7298e24f904224fa79eb8fd7e0fbd78950ccf2db

--
Thanks,
Sasha