Guillaume Nault eed4d839b0 l2tp: fix race while getting PMTU on PPP pseudo-wire ... Use dst_entry held by sk_dst_get() to retrieve tunnel's PMTU. The dst_mtu(__sk_dst_get(tunnel->sock)) call was racy. __sk_dst_get() could return NULL if tunnel->sock->sk_dst_cache was reset just before the call, thus making dst_mtu() dereference a NULL pointer: [ 1937.661598] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 [ 1937.664005] IP: [<ffffffffa049db88>] pppol2tp_connect+0x33d/0x41e [l2tp_ppp] [ 1937.664005] PGD daf0c067 PUD d9f93067 PMD 0 [ 1937.664005] Oops: 0000 [#1] SMP [ 1937.664005] Modules linked in: l2tp_ppp l2tp_netlink l2tp_core ip6table_filter ip6_tables iptable_filter ip_tables ebtable_nat ebtables x_tables udp_tunnel pppoe pppox ppp_generic slhc deflate ctr twofish_generic twofish_x86_64_3way xts lrw gf128mul glue_helper twofish_x86_64 twofish_common blowfish_generic blowfish_x86_64 blowfish_common des_generic cbc xcbc rmd160 sha512_generic hmac crypto_null af_key xfrm_algo 8021q garp bridge stp llc tun atmtcp clip atm ext3 mbcache jbd iTCO_wdt coretemp kvm_intel iTCO_vendor_support kvm pcspkr evdev ehci_pci lpc_ich mfd_core i5400_edac edac_core i5k_amb shpchp button processor thermal_sys xfs crc32c_generic libcrc32c dm_mod usbhid sg hid sr_mod sd_mod cdrom crc_t10dif crct10dif_common ata_generic ahci ata_piix tg3 libahci libata uhci_hcd ptp ehci_hcd pps_core usbcore scsi_mod libphy usb_common [last unloaded: l2tp_core] [ 1937.664005] CPU: 0 PID: 10022 Comm: l2tpstress Tainted: G O 3.17.0-rc1 #1 [ 1937.664005] Hardware name: HP ProLiant DL160 G5, BIOS O12 08/22/2008 [ 1937.664005] task: ffff8800d8fda790 ti: ffff8800c43c4000 task.ti: ffff8800c43c4000 [ 1937.664005] RIP: 0010:[<ffffffffa049db88>] [<ffffffffa049db88>] pppol2tp_connect+0x33d/0x41e [l2tp_ppp] [ 1937.664005] RSP: 0018:ffff8800c43c7de8 EFLAGS: 00010282 [ 1937.664005] RAX: ffff8800da8a7240 RBX: ffff8800d8c64600 RCX: 000001c325a137b5 [ 1937.664005] RDX: 8c6318c6318c6320 RSI: 000000000000010c RDI: 0000000000000000 [ 1937.664005] RBP: ffff8800c43c7ea8 R08: 0000000000000000 R09: 0000000000000000 [ 1937.664005] R10: ffffffffa048e2c0 R11: ffff8800d8c64600 R12: ffff8800ca7a5000 [ 1937.664005] R13: ffff8800c439bf40 R14: 000000000000000c R15: 0000000000000009 [ 1937.664005] FS: 00007fd7f610f700(0000) GS:ffff88011a600000(0000) knlGS:0000000000000000 [ 1937.664005] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 1937.664005] CR2: 0000000000000020 CR3: 00000000d9d75000 CR4: 00000000000027e0 [ 1937.664005] Stack: [ 1937.664005] ffffffffa049da80 ffff8800d8fda790 000000000000005b ffff880000000009 [ 1937.664005] ffff8800daf3f200 0000000000000003 ffff8800c43c7e48 ffffffff81109b57 [ 1937.664005] ffffffff81109b0e ffffffff8114c566 0000000000000000 0000000000000000 [ 1937.664005] Call Trace: [ 1937.664005] [<ffffffffa049da80>] ? pppol2tp_connect+0x235/0x41e [l2tp_ppp] [ 1937.664005] [<ffffffff81109b57>] ? might_fault+0x9e/0xa5 [ 1937.664005] [<ffffffff81109b0e>] ? might_fault+0x55/0xa5 [ 1937.664005] [<ffffffff8114c566>] ? rcu_read_unlock+0x1c/0x26 [ 1937.664005] [<ffffffff81309196>] SYSC_connect+0x87/0xb1 [ 1937.664005] [<ffffffff813e56f7>] ? sysret_check+0x1b/0x56 [ 1937.664005] [<ffffffff8107590d>] ? trace_hardirqs_on_caller+0x145/0x1a1 [ 1937.664005] [<ffffffff81213dee>] ? trace_hardirqs_on_thunk+0x3a/0x3f [ 1937.664005] [<ffffffff8114c262>] ? spin_lock+0x9/0xb [ 1937.664005] [<ffffffff813092b4>] SyS_connect+0x9/0xb [ 1937.664005] [<ffffffff813e56d2>] system_call_fastpath+0x16/0x1b [ 1937.664005] Code: 10 2a 84 81 e8 65 76 bd e0 65 ff 0c 25 10 bb 00 00 4d 85 ed 74 37 48 8b 85 60 ff ff ff 48 8b 80 88 01 00 00 48 8b b8 10 02 00 00 <48> 8b 47 20 ff 50 20 85 c0 74 0f 83 e8 28 89 83 10 01 00 00 89 [ 1937.664005] RIP [<ffffffffa049db88>] pppol2tp_connect+0x33d/0x41e [l2tp_ppp] [ 1937.664005] RSP <ffff8800c43c7de8> [ 1937.664005] CR2: 0000000000000020 [ 1939.559375] ---[ end trace 82d44500f28f8708 ]--- Fixes: f34c4a35d8 ("l2tp: take PMTU from tunnel UDP socket") Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2014-09-05 14:40:18 -07:00
..
Kconfig	l2tp: Call udp_sock_create	2014-07-14 16:12:15 -07:00
l2tp_core.c	l2tp: Call udp_sock_create	2014-07-14 16:12:15 -07:00
l2tp_core.h	l2tp: Add support for zero IPv6 checksums	2014-05-23 16:28:53 -04:00
l2tp_debugfs.c	ipv6: make lookups simpler and faster	2013-10-09 00:01:25 -04:00
l2tp_eth.c	net: set name_assign_type in alloc_netdev()	2014-07-15 16:12:48 -07:00
l2tp_ip6.c	net: use inet6_iif instead of IP6CB()->iif	2014-07-31 22:37:06 -07:00
l2tp_ip.c	net: Eliminate no_check from protosw	2014-05-23 16:28:53 -04:00
l2tp_netlink.c	l2tp: Add support for zero IPv6 checksums	2014-05-23 16:28:53 -04:00
l2tp_ppp.c	l2tp: fix race while getting PMTU on PPP pseudo-wire	2014-09-05 14:40:18 -07:00
Makefile	l2tp: introduce L2TPv3 IP encapsulation support for IPv6	2012-05-01 09:30:55 -04:00