syzbot


KASAN: use-after-free Read in pppol2tp_session_init

Status: auto-closed as invalid on 2020/12/20 11:25
Reported-by: syzbot+bd33c6379d2f0f4a7217@syzkaller.appspotmail.com
First crash: 676d, last: 676d
similar bugs (1):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: use-after-free Read in pppol2tp_session_init (2) C 10 11d 531d 0/1 upstream: reported C repro on 2021/01/14 16:13

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: use-after-free in sk_dst_get include/net/sock.h:1769 [inline]
BUG: KASAN: use-after-free in pppol2tp_session_init+0x4b4/0x4d0 net/l2tp/l2tp_ppp.c:616
Read of size 8 at addr ffff88808e811268 by task syz-executor.0/17532

CPU: 0 PID: 17532 Comm: syz-executor.0 Not tainted 4.14.194-syzkaller #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+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
 __read_once_size include/linux/compiler.h:183 [inline]
 sk_dst_get include/net/sock.h:1769 [inline]
 pppol2tp_session_init+0x4b4/0x4d0 net/l2tp/l2tp_ppp.c:616
 pppol2tp_connect+0xd11/0x1370 net/l2tp/l2tp_ppp.c:790
 SYSC_connect net/socket.c:1655 [inline]
 SyS_connect+0x1f4/0x240 net/socket.c:1636
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45d4d9
RSP: 002b:00007feb18234c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00000000000025c0 RCX: 000000000045d4d9
RDX: 000000000000002e RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffd68c0329f R14: 00007feb182359c0 R15: 000000000118cf4c

Allocated by task 17513:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
 sk_prot_alloc+0x5f/0x290 net/core/sock.c:1461
 sk_alloc+0x36/0xcd0 net/core/sock.c:1521
 inet6_create net/ipv6/af_inet6.c:183 [inline]
 inet6_create+0x2df/0xe20 net/ipv6/af_inet6.c:110
 __sock_create+0x303/0x620 net/socket.c:1275
 sock_create net/socket.c:1315 [inline]
 SYSC_socket net/socket.c:1345 [inline]
 SyS_socket+0xd1/0x1b0 net/socket.c:1325
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 3654:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758
 sk_prot_free net/core/sock.c:1502 [inline]
 __sk_destruct+0x42a/0x6e0 net/core/sock.c:1582
 sk_destruct net/core/sock.c:1597 [inline]
 __sk_free+0xd9/0x2d0 net/core/sock.c:1605
 sk_free+0x2b/0x40 net/core/sock.c:1616
 sock_put include/net/sock.h:1662 [inline]
 l2tp_session_free+0x1a0/0x200 net/l2tp/l2tp_core.c:1718
 l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:303 [inline]
 pppol2tp_session_destruct+0xcd/0x110 net/l2tp/l2tp_ppp.c:467
 __sk_destruct+0x49/0x6e0 net/core/sock.c:1557
 sk_destruct net/core/sock.c:1597 [inline]
 __sk_free+0xd9/0x2d0 net/core/sock.c:1605
 sk_free+0x2b/0x40 net/core/sock.c:1616
 sock_put include/net/sock.h:1662 [inline]
 pppol2tp_put_sk+0x4c/0x60 net/l2tp/l2tp_ppp.c:476
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2699 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline]
 rcu_process_callbacks+0x780/0x1180 kernel/rcu/tree.c:2946
 __do_softirq+0x254/0xa1d kernel/softirq.c:288

The buggy address belongs to the object at ffff88808e811040
 which belongs to the cache UDPv6 of size 1728
The buggy address is located 552 bytes inside of
 1728-byte region [ffff88808e811040, ffff88808e811700)
The buggy address belongs to the page:
page:ffffea00023a0440 count:1 mapcount:0 mapping:ffff88808e811040 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff88808e811040 0000000000000000 0000000100000002
raw: ffffea00027aec60 ffff88809b116448 ffff88809b227a80 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808e811100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808e811180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88808e811200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff88808e811280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808e811300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci2-linux-4-14 2020/08/22 11:24 linux-4.14.y 6a24ca2506d6 6436ce4b .config log report