bisecting fixing commit since 01364dad1d4577e27a57729d41053f661bb8a5b9
building syzkaller on 84f999d6319b21d9567132bf7ed26507f6d24310
testing commit 01364dad1d4577e27a57729d41053f661bb8a5b9 with gcc (GCC) 8.1.0
kernel signature: 6062e2b5eea6392fc8803e446e2a18f2c30256c1816a2927fc0d4d05792633c6
run #0: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge
run #1: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge
run #2: crashed: WARNING: held lock freed in pppol2tp_release
run #3: crashed: WARNING: held lock freed in pppol2tp_release
run #4: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge
run #5: crashed: WARNING: held lock freed in pppol2tp_release
run #6: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge
run #7: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge
run #8: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge
run #9: crashed: KASAN: use-after-free Read in l2tp_session_queue_purge
testing current HEAD b850307b279cbd12ab8c654d1a3dfe55319cc475
testing commit b850307b279cbd12ab8c654d1a3dfe55319cc475 with gcc (GCC) 8.1.0
kernel signature: 62c168f0343868ddf84479f31870a251bc39b61cfc019c830e0f3efbdebdfc77
run #0: crashed: general protection fault in pppol2tp_session_init
run #1: crashed: general protection fault in pppol2tp_session_init
run #2: crashed: KASAN: use-after-free Read in pppol2tp_session_init
run #3: crashed: general protection fault in pppol2tp_session_init
run #4: crashed: general protection fault in pppol2tp_session_init
run #5: crashed: general protection fault in pppol2tp_session_init
run #6: crashed: general protection fault in pppol2tp_session_init
run #7: crashed: general protection fault in pppol2tp_session_init
run #8: crashed: general protection fault in pppol2tp_session_init
run #9: crashed: general protection fault in pppol2tp_session_init
revisions tested: 2, total time: 26m38.259341455s (build: 17m30.812842674s, test: 7m42.22215564s)
the crash still happens on HEAD
commit msg: Linux 4.14.184
crash: general protection fault in pppol2tp_session_init
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 30622 Comm: syz-executor.2 Not tainted 4.14.184-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff888094e94080 task.stack: ffff888097c38000
RIP: 0010:__read_once_size include/linux/compiler.h:183 [inline]
RIP: 0010:sk_dst_get include/net/sock.h:1766 [inline]
RIP: 0010:pppol2tp_session_init+0x1c1/0x480 net/l2tp/l2tp_ppp.c:616
RSP: 0018:ffff888097c3fb90 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8880a7f3f6c0 RCX: 1ffffffff0f74dad
RDX: 0000000000000045 RSI: ffffffff87040380 RDI: 0000000000000228
RBP: ffff888097c3fbb8 R08: ffff888094e94950 R09: 0000000000000000
R10: 0000000000000028 R11: ffff888094e94080 R12: 0000000000000000
R13: 000000000000779e R14: ffff88809fb8aec0 R15: ffff8880a7f3f850
FS:  00007f1a99a01700(0000) GS:ffff8880aed00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efd8e24c022 CR3: 00000000a5fff000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 pppol2tp_connect+0xd08/0x1480 net/l2tp/l2tp_ppp.c:790
 SYSC_connect+0x1e3/0x2a0 net/socket.c:1655
 SyS_connect+0x9/0x10 net/socket.c:1636
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45c849
RSP: 002b:00007f1a99a00c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f1a99a016d4 RCX: 000000000045c849
RDX: 000000000000002e RSI: 0000000020000000 RDI: 0000000000000004
RBP: 000000000076bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000008d R14: 00000000004c324b R15: 000000000076bf0c
Code: 5a 85 c0 74 0d 80 3d 10 94 c0 02 00 0f 84 0c 02 00 00 49 8d bc 24 28 02 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 8d 02 00 00 4d 8b b4 24 28 02 00 00 e8 98 74 
RIP: __read_once_size include/linux/compiler.h:183 [inline] RSP: ffff888097c3fb90
RIP: sk_dst_get include/net/sock.h:1766 [inline] RSP: ffff888097c3fb90
RIP: pppol2tp_session_init+0x1c1/0x480 net/l2tp/l2tp_ppp.c:616 RSP: ffff888097c3fb90
---[ end trace 03ff800eed9dba67 ]---