syzbot


BUG: unable to handle kernel NULL pointer dereference in l2tp_session_free

Status: upstream: reported C repro on 2019/12/27 14:04
Reported-by: syzbot+9ea85809e818c6933f7b@syzkaller.appspotmail.com
First crash: 1641d, last: 1492d
Fix bisection the fix commit could be any of (bisect log):
  01364dad1d45 Linux 4.14.174
  4139fb08c05f Linux 4.14.187
  
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-44 BUG: unable to handle kernel NULL pointer dereference in l2tp_session_free C 23 2130d 1900d 0/2 public: reported C repro on 2019/04/13 00:00
android-49 BUG: unable to handle kernel NULL pointer dereference in l2tp_session_free C 2818 2126d 1901d 0/3 public: reported C repro on 2019/04/12 00:00
Last patch testing requests (2)
Created Duration User Patch Repo Result
2022/12/15 12:31 10m retest repro linux-4.14.y report log
2022/08/29 17:27 11m retest repro linux-4.14.y report log
Fix bisection attempts (2)
Created Duration User Patch Repo Result
2020/06/23 10:47 31m (4) bisect fix linux-4.14.y job log (2)
2020/05/03 20:05 24m bisect fix linux-4.14.y job log (0) log

Sample crash report:
audit: type=1400 audit(1584781951.932:36): avc:  denied  { map } for  pid=7523 comm="syz-executor775" path="/root/syz-executor775765992" dev="sda1" ino=16484 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
BUG: unable to handle kernel NULL pointer dereference at 0000000000000080
IP: refcount_dec_and_test arch/x86/include/asm/refcount.h:75 [inline]
IP: sock_put include/net/sock.h:1657 [inline]
IP: l2tp_session_free+0x113/0x200 net/l2tp/l2tp_core.c:1714
PGD 0 P4D 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 0 PID: 7525 Comm: syz-executor775 Not tainted 4.14.174-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8880a946c180 task.stack: ffff888088d88000
RIP: 0010:refcount_dec_and_test arch/x86/include/asm/refcount.h:75 [inline]
RIP: 0010:sock_put include/net/sock.h:1657 [inline]
RIP: 0010:l2tp_session_free+0x113/0x200 net/l2tp/l2tp_core.c:1714
RSP: 0018:ffff888088d8fbc0 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff8880a67842c0 RCX: 0000000000000000
RDX: 1ffff11014cf0889 RSI: ffff8880a946ca00 RDI: ffff8880a6784448
RBP: ffff88809903dac0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88809903dad0
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88809b4a4290
FS:  00000000017a9880(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000080 CR3: 0000000007c6a000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 l2tp_session_dec_refcount_1 net/l2tp/l2tp_core.h:300 [inline]
 pppol2tp_session_destruct+0xcd/0x110 net/l2tp/l2tp_ppp.c:460
 __sk_destruct+0x49/0x640 net/core/sock.c:1556
 sk_destruct+0x97/0xc0 net/core/sock.c:1596
 __sk_free+0x4c/0x220 net/core/sock.c:1604
 sk_free+0x2b/0x40 net/core/sock.c:1615
 sock_put include/net/sock.h:1658 [inline]
 pppol2tp_release+0x247/0x2f0 net/l2tp/l2tp_ppp.c:501
 __sock_release+0xcd/0x2b0 net/socket.c:602
 sock_close+0x15/0x20 net/socket.c:1139
 __fput+0x25f/0x790 fs/file_table.c:210
 task_work_run+0x113/0x190 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x9f2/0x2b00 kernel/exit.c:858
 do_group_exit+0x100/0x310 kernel/exit.c:955
 SYSC_exit_group kernel/exit.c:966 [inline]
 SyS_exit_group+0x19/0x20 kernel/exit.c:964
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x43ff48
RSP: 002b:00007fff68d6a498 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ff48
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004bf7d0 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000020000040 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d1180 R14: 0000000000000000 R15: 0000000000000000
Code: 97 fb 48 8d bb 88 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 d2 00 00 00 4c 8b ab 88 01 00 00 <f0> 41 ff 8d 80 00 00 00 0f 88 24 80 7b 00 74 70 e8 b8 d9 97 fb 
RIP: refcount_dec_and_test arch/x86/include/asm/refcount.h:75 [inline] RSP: ffff888088d8fbc0
RIP: sock_put include/net/sock.h:1657 [inline] RSP: ffff888088d8fbc0
RIP: l2tp_session_free+0x113/0x200 net/l2tp/l2tp_core.c:1714 RSP: ffff888088d8fbc0
CR2: 0000000000000080
---[ end trace d8b0b59e1be263bf ]---

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/03/21 09:15 linux-4.14.y 01364dad1d45 aa6c6a55 .config console log report syz C ci2-linux-4-14
2020/05/24 10:47 linux-4.14.y a41ba30d9df2 96c92ad3 .config console log report ci2-linux-4-14
2020/04/03 20:01 linux-4.14.y 4520f06b03ae 5ed396e6 .config console log report ci2-linux-4-14
2020/03/21 08:41 linux-4.14.y 01364dad1d45 aa6c6a55 .config console log report ci2-linux-4-14
2019/12/27 14:03 linux-4.14.y e1f7d50ae3a3 be5c2c81 .config console log report ci2-linux-4-14
* Struck through repros no longer work on HEAD.