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KASAN: use-after-free Read in pppol2tp_connect

Status: upstream: reported syz repro on 2019/09/25 11:59
Reported-by: syzbot+1103ad221a6999d73f67@syzkaller.appspotmail.com
First crash: 1884d, last: 1636d
Fix bisection the fix commit could be any of (bisect log):
  f6e27dbb1afa Linux 4.14.146
  4139fb08c05f Linux 4.14.187
   
▶ ▼ Similar bugs (5)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-49 KASAN: use-after-free Read in pppol2tp_connect 8 2293d 2498d 0/3 auto-closed as invalid on 2019/02/22 12:37
android-44 KASAN: use-after-free Read in pppol2tp_connect C 28 2276d 2049d 0/2 public: reported C repro on 2019/04/13 00:00
upstream KASAN: use-after-free Read in pppol2tp_connect (2) net C 10 2435d 2451d 4/28 fixed on 2018/03/23 18:14
upstream KASAN: use-after-free Read in pppol2tp_connect (3) net C 22 2415d 2433d 5/28 fixed on 2018/05/08 18:30
upstream KASAN: use-after-free Read in pppol2tp_connect net C 25 2452d 2501d 4/28 fixed on 2018/03/06 13:29
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2023/01/01 12:31 12m retest repro linux-4.14.y report log
2022/09/01 06:27 10m retest repro linux-4.14.y report log
▶ ▼ Fix bisection attempts (6)
Created Duration User Patch Repo Result
2020/06/29 09:45 29m (3) bisect fix linux-4.14.y OK (2) job log
2020/05/30 09:23 22m bisect fix linux-4.14.y OK (0) job log log
2020/04/10 12:50 23m bisect fix linux-4.14.y OK (0) job log log
2020/02/15 02:13 24m bisect fix linux-4.14.y OK (0) job log log
2020/01/16 00:23 24m bisect fix linux-4.14.y OK (0) job log log
2019/12/16 18:36 24m bisect fix linux-4.14.y OK (0) job log log

Sample crash report:
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
l2tp_core: tunl 4: sockfd_lookup(fd=4) returned -9
==================================================================
BUG: KASAN: use-after-free in pppol2tp_connect+0x169c/0x18b0 net/l2tp/l2tp_ppp.c:764
Read of size 8 at addr ffff888073c39858 by task syz-executor.5/8995

CPU: 0 PID: 8995 Comm: syz-executor.5 Not tainted 4.14.146 #0
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+0x138/0x197 lib/dump_stack.c:53
 print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 pppol2tp_connect+0x169c/0x18b0 net/l2tp/l2tp_ppp.c:764
 SYSC_connect+0x1f6/0x2d0 net/socket.c:1655
 SyS_connect+0x24/0x30 net/socket.c:1636
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x459a29
RSP: 002b:00007fabb543ac78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459a29
RDX: 0000000000000026 RSI: 0000000020000180 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fabb543b6d4
R13: 00000000004bff90 R14: 00000000004d1f00 R15: 00000000ffffffff

Allocated by task 8995:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc mm/kasan/kasan.c:551 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
 __do_kmalloc mm/slab.c:3720 [inline]
 __kmalloc+0x15d/0x7a0 mm/slab.c:3729
 kmalloc include/linux/slab.h:493 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 l2tp_session_create+0x38/0x1600 net/l2tp/l2tp_core.c:1791
 pppol2tp_connect+0x11bf/0x18b0 net/l2tp/l2tp_ppp.c:721
 SYSC_connect+0x1f6/0x2d0 net/socket.c:1655
 SyS_connect+0x24/0x30 net/socket.c:1636
 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 9004:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x45/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xcc/0x270 mm/slab.c:3815
 l2tp_session_free+0x176/0x210 net/l2tp/l2tp_core.c:1714
 l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:300 [inline]
 l2tp_tunnel_closeall+0x2ca/0x380 net/l2tp/l2tp_core.c:1345
 l2tp_udp_encap_destroy+0x99/0x100 net/l2tp/l2tp_core.c:1366
 udpv6_destroy_sock+0xb3/0xd0 net/ipv6/udp.c:1444
 sk_common_release+0x6b/0x310 net/core/sock.c:2984
 udp_lib_close+0x16/0x20 include/net/udp.h:203
 inet_release+0xec/0x1c0 net/ipv4/af_inet.c:425
 inet6_release+0x53/0x80 net/ipv6/af_inet6.c:450
 __sock_release+0xce/0x2b0 net/socket.c:602
 sock_close+0x1b/0x30 net/socket.c:1139
 __fput+0x275/0x7a0 fs/file_table.c:210
 ____fput+0x16/0x20 fs/file_table.c:244
 task_work_run+0x114/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x1da/0x220 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x4bc/0x640 arch/x86/entry/common.c:297
 entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff888073c39840
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
 512-byte region [ffff888073c39840, ffff888073c39a40)
The buggy address belongs to the page:
page:ffffea0001cf0e40 count:1 mapcount:0 mapping:ffff888073c390c0 index:0x0
flags: 0x1fffc0000000100(slab)
raw: 01fffc0000000100 ffff888073c390c0 0000000000000000 0000000100000006
raw: ffffea00025a6520 ffffea0001d129a0 ffff8880aa800940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888073c39700: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
 ffff888073c39780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888073c39800: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                    ^
 ffff888073c39880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888073c39900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/09/25 10:58 linux-4.14.y f6e27dbb1afa e38a6630 .config console log report syz ci2-linux-4-14
2020/04/30 09:22 linux-4.14.y 050272a0423e 2dd552a5 .config console log report ci2-linux-4-14
2020/03/11 11:43 linux-4.14.y 78d697fc93f9 e103bc9e .config console log report ci2-linux-4-14
2020/03/04 23:16 linux-4.14.y 78d697fc93f9 576fb9bc .config console log report ci2-linux-4-14
2020/03/03 20:37 linux-4.14.y 78d697fc93f9 1f73b64b .config console log report ci2-linux-4-14
2020/02/27 21:48 linux-4.14.y 98db2bf27b9e c88c7b75 .config console log report ci2-linux-4-14
2020/02/25 22:41 linux-4.14.y 98db2bf27b9e 4c886d6a .config console log report ci2-linux-4-14
* Struck through repros no longer work on HEAD.