[+Cc userfaultfd developers and linux-mm] The reproducer hits the BUG_ON() in userfaultfd_release(): BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); On Sun, Jul 15, 2018 at 05:19:03PM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 37b5dca2898d Merge tag 'rtc-4.18-2' of git://git.kernel.or.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=12aaf3b2400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=25856fac4e580aa7 > dashboard link: https://syzkaller.appspot.com/bug?extid=121be635a7a35ddb7dcb > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=11176d62400000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1362b368400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+121be635a7a35ddb7dcb@xxxxxxxxxxxxxxxxxxxxxxxxx > > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > random: sshd: uninitialized urandom read (32 bytes read) > ------------[ cut here ]------------ > kernel BUG at fs/userfaultfd.c:883! > invalid opcode: 0000 [#1] SMP KASAN > CPU: 0 PID: 4708 Comm: syz-executor086 Not tainted 4.18.0-rc4+ #148 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:userfaultfd_release+0x5fb/0x770 fs/userfaultfd.c:882 > Code: 00 31 c0 48 8b 4d d0 65 48 33 0c 25 28 00 00 00 0f 85 a1 00 00 00 48 > 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 75 be a0 ff <0f> 0b 4c 89 f7 e8 > 0b 9e de ff e9 11 fc ff ff 4c 89 e7 e8 5e 9d de > RSP: 0018:ffff8801d8407a80 EFLAGS: 00010293 > RAX: ffff8801d8742080 RBX: dffffc0000000000 RCX: ffffffff81db4a59 > RDX: 0000000000000000 RSI: ffffffff81db4ccb RDI: 0000000000000000 > RBP: ffff8801d8407bd0 R08: ffff8801d8742080 R09: 0000000000000000 > R10: ffff8801d87428b8 R11: 16fb0df9f74494d6 R12: ffff8801d89a3b58 > R13: 0000000000000000 R14: ffff8801d89a3a50 R15: 0000000000000000 > FS: 0000000000ed6880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f45c6b81e78 CR3: 00000001acb61000 CR4: 00000000001406f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > __fput+0x355/0x8b0 fs/file_table.c:209 > ____fput+0x15/0x20 fs/file_table.c:243 > task_work_run+0x1ec/0x2a0 kernel/task_work.c:113 > tracehook_notify_resume include/linux/tracehook.h:192 [inline] > exit_to_usermode_loop+0x313/0x370 arch/x86/entry/common.c:166 > prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] > syscall_return_slowpath arch/x86/entry/common.c:268 [inline] > do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x405471 > Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 54 17 00 00 c3 48 > 83 ec 08 e8 6a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 > c2 e8 b3 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 > RSP: 002b:00007ffcad3db600 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 > RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000405471 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005 > RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 > R10: 00007ffcad3db610 R11: 0000000000000293 R12: 00000000006dbc3c > R13: 00000000006dbda0 R14: 0000000000000008 R15: 0000000000000001 > Modules linked in: > Dumping ftrace buffer: > (ftrace buffer empty) > ---[ end trace 638e68cedadb8eda ]--- > RIP: 0010:userfaultfd_release+0x5fb/0x770 fs/userfaultfd.c:882 > Code: 00 31 c0 48 8b 4d d0 65 48 33 0c 25 28 00 00 00 0f 85 a1 00 00 00 48 > 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 75 be a0 ff <0f> 0b 4c 89 f7 e8 > 0b 9e de ff e9 11 fc ff ff 4c 89 e7 e8 5e 9d de > RSP: 0018:ffff8801d8407a80 EFLAGS: 00010293 > RAX: ffff8801d8742080 RBX: dffffc0000000000 RCX: ffffffff81db4a59 > RDX: 0000000000000000 RSI: ffffffff81db4ccb RDI: 0000000000000000 > RBP: ffff8801d8407bd0 R08: ffff8801d8742080 R09: 0000000000000000 > R10: ffff8801d87428b8 R11: 16fb0df9f74494d6 R12: ffff8801d89a3b58 > R13: 0000000000000000 R14: ffff8801d89a3a50 R15: 0000000000000000 > FS: 0000000000ed6880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f45c6b81e78 CR3: 00000001acb61000 CR4: 00000000001406f0 > 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@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this bug report. See: > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with > syzbot. > syzbot can test patches for this bug, for details see: > https://goo.gl/tpsmEJ#testing-patches > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/000000000000dcb1a1057112c66a%40google.com. > For more options, visit https://groups.google.com/d/optout.
