f3c66d4e144a0904ea9b95d23ed9f8eb38c11bfb l2tp: prevent creation of sessions on terminated tunnels 9ee369a405c57613d7c83a3967780c3e30c52ecc l2tp: initialise session's refcount before making it reachable dbdbc73b44782e22b3b4b6e8b51e7a3d245f3086 l2tp: fix duplicate session creation 61b9a047729bb230978178bca6729689d0c50ca2 l2tp: fix race in l2tp_recv_common()
For v3.18+. It requires some minor backporting.
Without these, I'm seeing a null pointer in l2tp_session_create. These logs are from a 3.18 kernel, although I was able to hit it on a 4.4 kernel I tested as well.
[ 376.388847] c1 11731 Unable to handle kernel NULL pointer dereference at virtual address 0000006c [ 376.388892] c1 11731 pgd = ffffffc093138000 [ 376.388908] [0000006c] *pgd=000000010add3003, *pud=000000010add3003, *pmd=0000000000000000 [ 376.388955] c1 11731 Internal error: Oops: 96000006 [#1] PREEMPT SMP [ 376.388987] c1 11731 CPU: 1 PID: 11731 Comm: 0 Tainted: G B W 3.18.31-g3021f2f-00001-gea07e56-dirty #35 [ 376.389005] c1 11731 Hardware name: HTC Corporation. MSM8996pro v1.1 + PMI8996 Marlin A (DT) [ 376.389024] c1 11731 task: ffffffc09f582880 ti: ffffffc089ea4000 task.ti: ffffffc089ea4000 [ 376.389062] c1 11731 PC is at l2tp_session_create+0x39c/0x5b8 [ 376.389081] c1 11731 LR is at l2tp_session_create+0x394/0x5b8 [ 376.389097] c1 11731 pc : [<ffffffc00127bbd4>] lr : [<ffffffc00127bbcc>] pstate: 20000145 [ 376.389112] c1 11731 sp : ffffffc089ea7ca0 [ 376.389127] x29: ffffffc089ea7ca0 x28: ffffffc03982fbf8 [ 376.389154] x27: 0000000000000000 x26: ffffffc03982fca0 [ 376.389180] x25: ffffffc099190ea8 x24: ffffffc03982fca8 [ 376.389205] x23: ffffffc03982fbf0 x22: 0000000000000000 [ 376.389230] x21: ffffffc03982fc98 x20: ffffffc099190e00 [ 376.389254] x19: ffffffc03982fb80 x18: ffffffc001bd00e0 [ 376.389277] x17: 0000000033293c44 x16: 000000006e1d9948 [ 376.389301] x15: 0000000000000000 x14: 000000000000000a [ 376.389324] x13: ffffffc0b982fc03 x12: 0000000000000000 [ 376.389347] x11: 0000000000000000 x10: ffffffc03982fc0d [ 376.389370] x9 : 00000000fffffffb x8 : ffffff8807305fb0 [ 376.389393] x7 : fcfcfcfcfcfcfcfc x6 : ffffffc03982fba4 [ 376.389415] x5 : 000000000000ffff x4 : ffffffc0019480db [ 376.389438] x3 : 1ffffff8132321e9 x2 : dfffff9000000000 [ 376.389461] x1 : 0000000000000000 x0 : 000000000000006c [ 376.389486] c1 11731 [ 376.389486] c1 11731 PC: 0xffffffc00127bad4: [ 376.389504] bad4 7900627b 91004b00 97bd0420 7940271b 9100d260 97bd043a 79006a7b 91004300 [ 376.389574] baf4 97bd041a 7940231b 9100ca60 97bd0434 7900667b 91007300 97bd044e b9401f1b [ 376.389641] bb14 91008260 97bd0469 b900227b 91005301 91006260 b9801f02 97bd05c4 9100a300 [ 376.389708] bb34 97bd0444 b9402b1b 9100b260 97bd045f b9002e7b 91008301 91009260 b9802b02 [ 376.389777] bb54 97bd05ba 97baedb0 9104a278 aa1903e0 97bd0438 b940aa80 7100081f 540009c1 [ 376.389843] bb74 97baeda9 aa1803e0 97bd048b 90ffffe0 91383000 f9009660 97baeda3 b940aa81 [ 376.389910] bb94 aa1303e0 97fffb38 91020262 885f7c40 11000400 88017c40 35ffffa1 9104a282 [ 376.389976] bbb4 885f7c40 11000400 88017c40 35ffffa1 91052280 97bd045b f940a680 9101b000 [ 376.390042] bbd4 885f7c01 11000421 88027c01 35ffffa2 9100629b aa1b03e0 94028720 52800020 [ 376.390107] bbf4 72b3c6e0 1b007ec0 b9006ba0 f94037a0 d35c7c16 910012c0 8b160e96 f90033a0 [ 376.390174] bc14 8b000e80 97bd0447 f94012d8 aa1703e0 97bd0461 f9003a78 b40000b8 97baed7a [ 376.390240] bc34 91002300 97bd045c f9000717 97baed76 f90012d7 aa1c03e0 97bd0457 f94033a0 [ 376.390306] bc54 8b000e80 f9003e60 aa1b03e0 94028827 aa1903e0 97bd03f7 b940aa80 7100081f [ 376.390372] bc74 54000920 97baed68 91048280 97bd042d f9409296 b50001d6 97baed63 e7f001f2 [ 376.390439] bc94 97baed61 aa1503e0 97bd0408 12bfe000 17ffff16 97baed5c aa1803e0 97bd043e [ 376.390508] bcb4 b0ffffe0 910f2000 17ffffb3 97baed56 d00065e0 b943a814 97ba0a9c 9134a2c0 [ 376.390576] c1 11731 [ 376.390576] c1 11731 LR: 0xffffffc00127bacc: [ 376.390594] bacc 9100c260 97bd0440 7900627b 91004b00 97bd0420 7940271b 9100d260 97bd043a [ 376.390662] baec 79006a7b 91004300 97bd041a 7940231b 9100ca60 97bd0434 7900667b 91007300 [ 376.390728] bb0c 97bd044e b9401f1b 91008260 97bd0469 b900227b 91005301 91006260 b9801f02 [ 376.390795] bb2c 97bd05c4 9100a300 97bd0444 b9402b1b 9100b260 97bd045f b9002e7b 91008301 [ 376.390862] bb4c 91009260 b9802b02 97bd05ba 97baedb0 9104a278 aa1903e0 97bd0438 b940aa80 [ 376.390929] bb6c 7100081f 540009c1 97baeda9 aa1803e0 97bd048b 90ffffe0 91383000 f9009660 [ 376.390995] bb8c 97baeda3 b940aa81 aa1303e0 97fffb38 91020262 885f7c40 11000400 88017c40 [ 376.391061] bbac 35ffffa1 9104a282 885f7c40 11000400 88017c40 35ffffa1 91052280 97bd045b [ 376.391128] bbcc f940a680 9101b000 885f7c01 11000421 88027c01 35ffffa2 9100629b aa1b03e0 [ 376.391195] bbec 94028720 52800020 72b3c6e0 1b007ec0 b9006ba0 f94037a0 d35c7c16 910012c0 [ 376.391262] bc0c 8b160e96 f90033a0 8b000e80 97bd0447 f94012d8 aa1703e0 97bd0461 f9003a78 [ 376.391328] bc2c b40000b8 97baed7a 91002300 97bd045c f9000717 97baed76 f90012d7 aa1c03e0 [ 376.391394] bc4c 97bd0457 f94033a0 8b000e80 f9003e60 aa1b03e0 94028827 aa1903e0 97bd03f7 [ 376.391461] bc6c b940aa80 7100081f 54000920 97baed68 91048280 97bd042d f9409296 b50001d6 [ 376.391528] bc8c 97baed63 e7f001f2 97baed61 aa1503e0 97bd0408 12bfe000 17ffff16 97baed5c [ 376.391594] bcac aa1803e0 97bd043e b0ffffe0 910f2000 17ffffb3 97baed56 d00065e0 b943a814 [ 376.391663] c1 11731 [ 376.391663] c1 11731 SP: 0xffffffc089ea7ba0: [ 376.391680] 7ba0 019480db ffffffc0 0000ffff 00000000 3982fba4 ffffffc0 fcfcfcfc fcfcfcfc [ 376.391747] 7bc0 07305fb0 ffffff88 fffffffb 00000000 3982fc0d ffffffc0 00000000 00000000 [ 376.391814] 7be0 00000000 00000000 b982fc03 ffffffc0 0000000a 00000000 00000000 00000000 [ 376.391880] 7c00 6e1d9948 00000000 33293c44 00000000 01bd00e0 ffffffc0 3982fb80 ffffffc0 [ 376.391947] 7c20 99190e00 ffffffc0 3982fc98 ffffffc0 00000000 00000000 3982fbf0 ffffffc0 [ 376.392013] 7c40 3982fca8 ffffffc0 99190ea8 ffffffc0 3982fca0 ffffffc0 00000000 00000000 [ 376.392078] 7c60 3982fbf8 ffffffc0 89ea7ca0 ffffffc0 0127bbcc ffffffc0 89ea7ca0 ffffffc0 [ 376.392144] 7c80 0127bbd4 ffffffc0 20000145 00000000 3982fc98 ffffffc0 00000000 00000000 [ 376.392212] 7ca0 89ea7d10 ffffffc0 0127dc2c ffffffc0 4261c200 ffffffc0 00000000 00000000 [ 376.392278] 7cc0 00000000 00000000 00000000 00000000 00000004 00000000 fffffff4 00000000 [ 376.392344] 7ce0 4261c230 ffffffc0 00000004 00000000 00000002 00000000 4261c212 ffffffc0 [ 376.392410] 7d00 89ea7d10 ffffffc0 00000000 ffffffc0 89ea7e00 ffffffc0 00ffd790 ffffffc0 [ 376.392478] 7d20 2aff8400 ffffffc0 00000026 00000000 3cf07980 ffffffc0 01bd0000 ffffffc0 [ 376.392544] 7d40 0127d9cc ffffffc0 00000015 00000000 00000119 00000000 000000cb 00000000 [ 376.392611] 7d60 01326000 ffffffc0 89ea4000 ffffffc0 01bd0000 ffffffc0 4261c448 ffffffc0 [ 376.392680] 7d80 00000003 00000000 99190e00 ffffffc0 ffffffff ffffffff 000cfb30 ffffffc0 [ 376.392747] c1 11731 [ 376.392765] c1 11731 Process 0 (pid: 11731, stack limit = 0xffffffc089ea4058) [ 376.392784] c1 11731 Context switch saved registers(0xffffffc09f582ec0 to 0xffffffc09f582f28) [ 376.392804] c1 11731 2ec0: a5f51b00 ffffffc0 9f582880 ffffffc0 89ea4000 ffffffc0 23966c00 ffffffc0 [ 376.392824] c1 11731 2ee0: 7345e780 ffffffc0 01c20000 ffffffc0 89ea7ac0 ffffffc0 019fe400 ffffffc0 [ 376.392842] c1 11731 2f00: 019fe400 ffffffc0 a5f51b00 ffffffc0 89ea7aa0 ffffffc0 89ea7aa0 ffffffc0 [ 376.392857] c1 11731 2f20: 00087574 ffffffc0 [ 376.392870] c1 11731 Call trace: [ 376.392904] c1 11731 [<ffffffc00127bbd4>] l2tp_session_create+0x39c/0x5b8 [ 376.392923] c1 11731 [<ffffffc00127dc2c>] pppol2tp_connect+0x260/0x698 [ 376.392952] c1 11731 [<ffffffc000ffd790>] SyS_connect+0xcc/0x144 [ 376.392971] c1 11731 Code: 91052280 97bd045b f940a680 9101b000 (885f7c01) [ 376.402888] c1 11731 ---[ end trace 7e40566c5e647ab7 ]--- [ 376.446227] c1 11731 Kernel panic - not syncing: Fatal exception