Hello,

syzbot found the following crash on:

HEAD commit: 0be0ee71 vfs: properly and reliably lock f_pos in fdget_po.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=12c49ef2e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=330a1f54d1edb817 dashboard link: https://syzkaller.appspot.com/bug?extid=131d2229316b7012ac06 compiler: clang version 9.0.0 (/home/glider/llvm/clang 80fee25776c2fb61e74c1ecb1a523375c2500b69) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13bb67cee00000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12460136e00000

The bug was bisected to:

commit 8ae5bcdc5d98a99e59f194101e7acd2e9d055758 Author: Vivien Didelot vivien.didelot@savoirfairelinux.com Date: Fri May 19 21:00:54 2017 +0000

net: dsa: add MDB notifier

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=17ec2f5ae00000 final crash: https://syzkaller.appspot.com/x/report.txt?x=141c2f5ae00000 console output: https://syzkaller.appspot.com/x/log.txt?x=101c2f5ae00000

IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+131d2229316b7012ac06@syzkaller.appspotmail.com Fixes: 8ae5bcdc5d98 ("net: dsa: add MDB notifier")

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 CPU: 1 PID: 7989 Comm: kworker/1:4 Not tainted 5.4.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: krxrpcd rxrpc_peer_keepalive_worker RIP: 0010:smack_socket_sendmsg+0x5b/0x480 security/smack/smack_lsm.c:3675 Code: e8 fa 03 6b fe 4c 89 e8 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 ef e8 74 46 a4 fe 4d 8b 65 00 48 83 c3 18 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 56 46 a4 fe 4c 8b 33 49 8d 9e 08 RSP: 0018:ffff88808a58f9c8 EFLAGS: 00010206 RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff8880a1270280 RDX: 0000000000000000 RSI: ffff88808a58fb18 RDI: 0000000000000000 RBP: ffff88808a58fa80 R08: ffffffff83442500 R09: ffff88808a58fb86 R10: ffffed10114b1f72 R11: 0000000000000000 R12: ffff8880a124c114 R13: ffff88808a58fb18 R14: dffffc0000000000 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe2d48c9e78 CR3: 0000000098a23000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: security_socket_sendmsg+0x6c/0xd0 security/security.c:2013 sock_sendmsg net/socket.c:655 [inline] kernel_sendmsg+0x77/0x140 net/socket.c:678 rxrpc_send_keepalive+0x254/0x3c0 net/rxrpc/output.c:655 rxrpc_peer_keepalive_dispatch net/rxrpc/peer_event.c:376 [inline] rxrpc_peer_keepalive_worker+0x76e/0xb40 net/rxrpc/peer_event.c:437 process_one_work+0x7ef/0x10e0 kernel/workqueue.c:2269 worker_thread+0xc01/0x1630 kernel/workqueue.c:2415 kthread+0x332/0x350 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Modules linked in: ---[ end trace 8b748724da7e3b28 ]--- RIP: 0010:smack_socket_sendmsg+0x5b/0x480 security/smack/smack_lsm.c:3675 Code: e8 fa 03 6b fe 4c 89 e8 48 c1 e8 03 42 80 3c 38 00 74 08 4c 89 ef e8 74 46 a4 fe 4d 8b 65 00 48 83 c3 18 48 89 d8 48 c1 e8 03 <42> 80 3c 38 00 74 08 48 89 df e8 56 46 a4 fe 4c 8b 33 49 8d 9e 08 RSP: 0018:ffff88808a58f9c8 EFLAGS: 00010206 RAX: 0000000000000003 RBX: 0000000000000018 RCX: ffff8880a1270280 RDX: 0000000000000000 RSI: ffff88808a58fb18 RDI: 0000000000000000 RBP: ffff88808a58fa80 R08: ffffffff83442500 R09: ffff88808a58fb86 R10: ffffed10114b1f72 R11: 0000000000000000 R12: ffff8880a124c114 R13: ffff88808a58fb18 R14: dffffc0000000000 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe2d48c9e78 CR3: 0000000098a23000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

--- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. For information about bisection process see: https://goo.gl/tpsmEJ#bisection syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches