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KASAN: use-after-free Read in pppol2tp_connect (2)

Status: fixed on 2018/03/23 18:14
Subsystems: net
[Documentation on labels]
Fix commit: 17cfe79a65f9 l2tp: do not accept arbitrary sockets
First crash: 2811d, last: 2796d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-49 KASAN: use-after-free Read in pppol2tp_connect 19 8 2654d 2859d 0/3 auto-closed as invalid on 2019/02/22 12:37
android-44 KASAN: use-after-free Read in pppol2tp_connect 19 C 28 2636d 2410d 0/2 public: reported C repro on 2019/04/13 00:00
linux-4.14 KASAN: use-after-free Read in pppol2tp_connect 19 syz inconclusive 7 1997d 2245d 0/1 upstream: reported syz repro on 2019/09/25 11:59
upstream KASAN: use-after-free Read in pppol2tp_connect (3) net 19 C 22 2776d 2794d 5/29 fixed on 2018/05/08 18:30
upstream KASAN: use-after-free Read in pppol2tp_connect net 19 C 25 2813d 2862d 4/29 fixed on 2018/03/06 13:29

Sample crash report:
l2tp_core: tunl 3: fd 3 wrong protocol, got 1, expected 17
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:188 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1766 [inline]
BUG: KASAN: use-after-free in pppol2tp_session_init net/l2tp/l2tp_ppp.c:587 [inline]
BUG: KASAN: use-after-free in pppol2tp_connect+0x1a98/0x1dd0 net/l2tp/l2tp_ppp.c:747
Read of size 8 at addr ffff8801ae8dea68 by task syzkaller185111/6389

CPU: 1 PID: 6389 Comm: syzkaller185111 Not tainted 4.16.0-rc5+ #354
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23c/0x360 mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 __read_once_size include/linux/compiler.h:188 [inline]
 sk_dst_get include/net/sock.h:1766 [inline]
 pppol2tp_session_init net/l2tp/l2tp_ppp.c:587 [inline]
 pppol2tp_connect+0x1a98/0x1dd0 net/l2tp/l2tp_ppp.c:747
 SYSC_connect+0x213/0x4a0 net/socket.c:1639
 SyS_connect+0x24/0x30 net/socket.c:1620
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x446bf9
RSP: 002b:00007fa8b6eaedb8 EFLAGS: 00000293 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00000000006e29e4 RCX: 0000000000446bf9
RDX: 0000000000000032 RSI: 0000000020e71000 RDI: 0000000000000006
RBP: 00000000006e29e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 00007ffd59befb1f R14: 00007fa8b6eaf9c0 R15: 0000000000000009

Allocated by task 6389:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3541
 sk_prot_alloc+0x65/0x2a0 net/core/sock.c:1465
 sk_alloc+0x105/0x1440 net/core/sock.c:1525
 inet6_create+0x44d/0x10f0 net/ipv6/af_inet6.c:183
 __sock_create+0x4d4/0x850 net/socket.c:1285
 sock_create net/socket.c:1325 [inline]
 SYSC_socket net/socket.c:1355 [inline]
 SyS_socket+0xeb/0x1d0 net/socket.c:1335
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 28:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kmem_cache_free+0x83/0x2a0 mm/slab.c:3743
 sk_prot_free net/core/sock.c:1506 [inline]
 __sk_destruct+0x628/0x920 net/core/sock.c:1590
 sk_destruct+0x47/0x80 net/core/sock.c:1598
 __sk_free+0xf1/0x2b0 net/core/sock.c:1609
 sk_free+0x2a/0x40 net/core/sock.c:1620
 sock_put include/net/sock.h:1658 [inline]
 l2tp_tunnel_free net/l2tp/l2tp_core.c:153 [inline]
 l2tp_tunnel_dec_refcount net/l2tp/l2tp_core.h:267 [inline]
 l2tp_tunnel_del_work+0x474/0x6a0 net/l2tp/l2tp_core.c:1291
 process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113
 worker_thread+0x223/0x1990 kernel/workqueue.c:2247
 kthread+0x33c/0x400 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

The buggy address belongs to the object at ffff8801ae8de840
 which belongs to the cache UDPv6 of size 1664
The buggy address is located 552 bytes inside of
 1664-byte region [ffff8801ae8de840, ffff8801ae8deec0)
The buggy address belongs to the page:
page:ffffea0006ba3780 count:1 mapcount:0 mapping:ffff8801ae8de140 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801ae8de140 0000000000000000 0000000100000002
raw: ffffea0006b5f9e0 ffffea0006c2dd60 ffff8801d1af8d80 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ae8de900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ae8de980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801ae8dea00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801ae8dea80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ae8deb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/03/15 14:31 upstream 0aa3fdb8b3a6 08dacaa0 .config console log report syz C ci-upstream-kasan-gce
2018/03/15 14:27 upstream 0aa3fdb8b3a6 08dacaa0 .config console log report syz ci-upstream-kasan-gce-386
2018/03/20 17:11 upstream 1b5f3ba415fe 72c33b66 .config console log report ci-upstream-kasan-gce
2018/03/19 13:19 upstream c698ca527893 7e7d7ed2 .config console log report ci-upstream-kasan-gce
2018/03/18 11:19 upstream 8f5fd927c3a7 08dacaa0 .config console log report ci-upstream-kasan-gce
2018/03/15 07:43 upstream 3032f8c504d2 08dacaa0 .config console log report ci-upstream-kasan-gce
2018/03/14 15:02 upstream fc6eabbbf8ef 08dacaa0 .config console log report ci-upstream-kasan-gce
2018/03/23 05:08 net-next-old 6686c459e144 2e9d9054 .config console log report ci-upstream-net-kasan-gce
2018/03/12 01:07 net-next-old f44b1886a5f8 36d1c454 .config console log report ci-upstream-net-kasan-gce
2018/03/07 20:09 net-next-old 30855ffc29b9 a5e76540 .config console log report ci-upstream-net-kasan-gce
* Struck through repros no longer work on HEAD.