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KASAN: use-after-free Read in l2tp_session_create

Status: fixed on 2018/07/20 18:40
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+065d0fc357520c8f6039@syzkaller.appspotmail.com
Fix commit: 6b9f34239b00 l2tp: fix races in tunnel creation
First crash: 2596d, last: 2529d
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
KASAN: use-after-free Read in l2tp_session_create 4 (5) 2018/07/20 09:49
▶ ▼ Similar bugs (3)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-44 KASAN: use-after-free Read in l2tp_session_create C 10 2371d 2569d 0/2 closed as invalid on 2019/03/26 00:01
android-49 KASAN: use-after-free Read in l2tp_session_create C 2 2371d 2143d 0/3 public: reported C repro on 2019/04/14 08:51
linux-4.14 KASAN: use-after-free Read in l2tp_session_create syz inconclusive 7 840d 2022d 0/1 upstream: reported syz repro on 2019/08/13 00:46

Sample crash report:
device eql entered promiscuous mode
==================================================================
BUG: KASAN: use-after-free in l2tp_session_create+0x9aa/0xb80 net/l2tp/l2tp_core.c:1749
Read of size 4 at addr ffff8801cca736a8 by task syz-executor1/5528

CPU: 0 PID: 5528 Comm: syz-executor1 Not tainted 4.16.0-rc2+ #323
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+0x194/0x257 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+0x23b/0x360 mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 l2tp_session_create+0x9aa/0xb80 net/l2tp/l2tp_core.c:1749
 pppol2tp_connect+0xed7/0x1dd0 net/l2tp/l2tp_ppp.c:748
 SYSC_connect+0x213/0x4a0 net/socket.c:1639
 SyS_connect+0x24/0x30 net/socket.c:1620
 do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x453da9
RSP: 002b:00007fd3883bac68 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007fd3883bb6d4 RCX: 0000000000453da9
RDX: 000000000000002e RSI: 0000000020e92000 RDI: 0000000000000015
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000005c R14: 00000000006f0940 R15: 0000000000000000

Allocated by task 5528:
 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
 kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3607
 kmalloc include/linux/slab.h:512 [inline]
 kzalloc include/linux/slab.h:701 [inline]
 l2tp_tunnel_create+0x5e1/0x17f0 net/l2tp/l2tp_core.c:1545
 pppol2tp_connect+0x14b1/0x1dd0 net/l2tp/l2tp_ppp.c:707
 SYSC_connect+0x213/0x4a0 net/socket.c:1639
 SyS_connect+0x24/0x30 net/socket.c:1620
 do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 5539:
 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]
 kfree+0xd9/0x260 mm/slab.c:3800
 __rcu_reclaim kernel/rcu/rcu.h:167 [inline]
 rcu_do_batch kernel/rcu/tree.c:2674 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2933 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2900 [inline]
 rcu_process_callbacks+0xe94/0x17f0 kernel/rcu/tree.c:2917
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801cca735c0
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 232 bytes inside of
 512-byte region [ffff8801cca735c0, ffff8801cca737c0)
The buggy address belongs to the page:
page:ffffea0007329cc0 count:1 mapcount:0 mapping:ffff8801cca730c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cca730c0 0000000000000000 0000000100000006
raw: ffffea0006d3ebe0 ffffea0007212f60 ffff8801db000940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cca73580: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8801cca73600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801cca73680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8801cca73700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801cca73780: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================

Crashes (119):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/02/21 09:09 upstream af3e79d29555 04cbdbd1 .config console log report ci-upstream-kasan-gce
2018/02/21 04:15 upstream af3e79d29555 04cbdbd1 .config console log report ci-upstream-kasan-gce
2018/02/21 03:19 upstream af3e79d29555 04cbdbd1 .config console log report ci-upstream-kasan-gce
2018/02/19 22:55 upstream 91ab883eb213 c1f526e3 .config console log report ci-upstream-kasan-gce
2018/02/18 17:18 upstream c786427f57b6 833f78c7 .config console log report ci-upstream-kasan-gce
2018/02/18 03:53 upstream ee78ad7848a7 833f78c7 .config console log report ci-upstream-kasan-gce
2018/02/17 12:11 upstream 1e3510b2b053 c8b3f7c1 .config console log report ci-upstream-kasan-gce
2018/02/17 05:40 upstream 1a2a7d3ee659 c8b3f7c1 .config console log report ci-upstream-kasan-gce
2018/02/16 00:03 upstream 1388c80438e6 c8b3f7c1 .config console log report ci-upstream-kasan-gce
2018/02/14 17:56 upstream 61f14c015f5b 17061fc0 .config console log report ci-upstream-kasan-gce
2018/02/14 10:11 upstream 61f14c015f5b 88bc17df .config console log report ci-upstream-kasan-gce
2018/02/12 22:19 upstream 178e834c47b0 88bc17df .config console log report ci-upstream-kasan-gce
2018/02/12 20:57 upstream 178e834c47b0 88bc17df .config console log report ci-upstream-kasan-gce
2018/02/11 21:27 upstream d48fcbd864a0 4e9b726d .config console log report ci-upstream-kasan-gce
2018/02/08 17:41 upstream 581e400ff935 9fb5ec43 .config console log report ci-upstream-kasan-gce
2018/02/07 09:44 upstream cbd7b8a76b79 66c15deb .config console log report ci-upstream-kasan-gce
2018/02/06 01:40 upstream 2deb41b24532 a1bc9d40 .config console log report ci-upstream-kasan-gce
2018/02/05 04:23 upstream 35277995e179 a1bc9d40 .config console log report ci-upstream-kasan-gce
2018/02/02 18:19 upstream 4bf772b14675 632a8c2c .config console log report ci-upstream-kasan-gce
2018/02/02 15:29 upstream 4bf772b14675 826b35d6 .config console log report ci-upstream-kasan-gce
2018/02/02 11:06 upstream 4bf772b14675 826b35d6 .config console log report ci-upstream-kasan-gce
2018/02/01 16:35 upstream 255442c93843 67bd3383 .config console log report ci-upstream-kasan-gce
2018/01/31 10:15 upstream 72906f38934a 02553e22 .config console log report ci-upstream-kasan-gce
2018/01/30 22:40 upstream 72906f38934a a899be78 .config console log report ci-upstream-kasan-gce
2018/01/30 22:37 upstream 72906f38934a a899be78 .config console log report ci-upstream-kasan-gce
2018/01/30 08:07 upstream 6304672b7f0a 08d47756 .config console log report ci-upstream-kasan-gce
2018/01/30 01:59 upstream d8a5b80568a9 08d47756 .config console log report ci-upstream-kasan-gce
2018/01/29 15:21 upstream d8a5b80568a9 08d47756 .config console log report ci-upstream-kasan-gce
2018/01/29 02:52 upstream 24b1cccf9229 08d47756 .config console log report ci-upstream-kasan-gce
2018/01/28 03:39 upstream c4e0ca7fa241 08146b1a .config console log report ci-upstream-kasan-gce
2018/01/27 11:11 upstream c4e0ca7fa241 1d18b112 .config console log report ci-upstream-kasan-gce
2018/01/26 17:30 upstream 993ca2068b04 1d18b112 .config console log report ci-upstream-kasan-gce
2018/01/26 13:20 upstream 993ca2068b04 1d18b112 .config console log report ci-upstream-kasan-gce
2018/01/25 03:07 upstream 5132ede0fe80 866f1102 .config console log report ci-upstream-kasan-gce
2018/01/22 22:37 upstream 0d665e7b109d 228e3d95 .config console log report ci-upstream-kasan-gce
2018/01/20 14:49 upstream 8dd903d2cf7b fbbdcd92 .config console log report ci-upstream-kasan-gce
2018/01/19 13:41 upstream dda3e15231b3 161c1d64 .config console log report ci-upstream-kasan-gce
2018/01/19 11:37 upstream dda3e15231b3 161c1d64 .config console log report ci-upstream-kasan-gce
2018/01/16 13:52 upstream a8750ddca918 4198e588 .config console log report ci-upstream-kasan-gce
2018/03/24 09:29 upstream 99fec39e7725 2e9d9054 .config console log report ci-upstream-kasan-gce-386
2018/03/10 21:41 upstream 3266b5bd97ea 36d1c454 .config console log report ci-upstream-kasan-gce-386
2018/02/16 15:27 upstream 1388c80438e6 c8b3f7c1 .config console log report ci-upstream-kasan-gce-386
2018/02/15 08:24 upstream e525de3ab046 77ed06bf .config console log report ci-upstream-kasan-gce-386
2018/03/21 22:20 net-next-old 454bfe97837a f63eeee9 .config console log report ci-upstream-net-kasan-gce
* Struck through repros no longer work on HEAD.