Messages in this thread | | | Subject | Re: general protection fault in open_fs_devices | From | Anand Jain <> | Date | Thu, 7 Jun 2018 00:28:48 +0800 |
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On 06/06/2018 09:17 PM, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: af6c5d5e01ad Merge branch 'for-4.18' of > git://git.kernel.o.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1732a6f7800000 > kernel config: https://syzkaller.appspot.com/x/.config?x=12ff770540994680 > dashboard link: > https://syzkaller.appspot.com/bug?extid=909a5177749d7990ffa4 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=16ba31f7800000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16d4ac8f800000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+909a5177749d7990ffa4@syzkaller.appspotmail.com > > random: sshd: uninitialized urandom read (32 bytes read) > BTRFS: device fsid ecf6f2a2-2997-48ae-b81e-1b00920efd9a devid 0 transid > 0 /dev/loop0 > print_req_error: I/O error, dev loop1, sector 128 > kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN > CPU: 0 PID: 4540 Comm: syz-executor962 Not tainted 4.17.0+ #86 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > RIP: 0010:open_fs_devices+0x7e8/0xc60 fs/btrfs/volumes.c:1124
Which means there was some other thread which freed our %fs_devices. As this thread is still in open_ctree() so the contending thread can't be the ioctl(). So btrfs_free_stale_devices() is the only thread which can free our %fs_devices in this case.
This is fixed in [1] in the mailing list.
[1] [PATCH 3/3] btrfs: fix race between mkfs and mount
Thanks, Anand
> Code: 48 8b 85 e0 fe ff ff 41 c7 87 14 01 00 00 01 00 00 00 48 8d b8 a0 > 00 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 01 04 00 00 48 8b 85 e0 fe ff ff 49 8d 7f 50 48 > RSP: 0018:ffff8801d06971d8 EFLAGS: 00010206 > RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff82c386af > RDX: 0000000000000014 RSI: ffffffff82c386bd RDI: 00000000000000a0 > RBP: ffff8801d0697348 R08: ffff8801ad4fc580 R09: ffff8801d0697240 > R10: ffffed003a0d2e5c R11: ffff8801d06972e7 R12: ffff8801ad4f8158 > R13: ffff8801ad4f80d8 R14: dffffc0000000000 R15: ffff8801ad4f8080 > FS: 00000000017dd880(0000) GS:ffff8801dae00000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000ede000 CR3: 00000001adaac000 CR4: 00000000001406f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > btrfs_open_devices+0xc0/0xd0 fs/btrfs/volumes.c:1155 > btrfs_mount_root+0x91f/0x1e70 fs/btrfs/super.c:1568 > mount_fs+0xae/0x328 fs/super.c:1277 > vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037 > vfs_kern_mount+0x40/0x60 fs/namespace.c:1027 > btrfs_mount+0x4a1/0x213e fs/btrfs/super.c:1661 > mount_fs+0xae/0x328 fs/super.c:1277 > vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037 > vfs_kern_mount fs/namespace.c:1027 [inline] > do_new_mount fs/namespace.c:2518 [inline] > do_mount+0x564/0x30b0 fs/namespace.c:2848 > ksys_mount+0x12d/0x140 fs/namespace.c:3064 > __do_sys_mount fs/namespace.c:3078 [inline] > __se_sys_mount fs/namespace.c:3075 [inline] > __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075 > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x4431fa > Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd e5 fb ff c3 66 2e > 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 > f0 ff ff 0f 83 da e5 fb ff c3 66 0f 1f 84 00 00 00 00 00 > RSP: 002b:00007ffc2d953358 EFLAGS: 00000297 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004431fa > RDX: 0000000020000080 RSI: 0000000020000040 RDI: 00007ffc2d953370 > RBP: 0000000000000004 R08: 00000000200000c0 R09: 000000000000000a > R10: 0000000000000000 R11: 0000000000000297 R12: 000000000000000d > R13: 0000000008100000 R14: 0030656c69662f2e R15: fe03f80fe03f80ff > Modules linked in: > Dumping ftrace buffer: > (ftrace buffer empty) > ---[ end trace d8b96c29a3ffd356 ]--- > RIP: 0010:open_fs_devices+0x7e8/0xc60 fs/btrfs/volumes.c:1124 > Code: 48 8b 85 e0 fe ff ff 41 c7 87 14 01 00 00 01 00 00 00 48 8d b8 a0 > 00 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 01 04 00 00 48 8b 85 e0 fe ff ff 49 8d 7f 50 48 > RSP: 0018:ffff8801d06971d8 EFLAGS: 00010206 > RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff82c386af > RDX: 0000000000000014 RSI: ffffffff82c386bd RDI: 00000000000000a0 > RBP: ffff8801d0697348 R08: ffff8801ad4fc580 R09: ffff8801d0697240 > R10: ffffed003a0d2e5c R11: ffff8801d06972e7 R12: ffff8801ad4f8158 > R13: ffff8801ad4f80d8 R14: dffffc0000000000 R15: ffff8801ad4f8080 > FS: 00000000017dd880(0000) GS:ffff8801dae00000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000ede000 CR3: 00000001adaac000 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@googlegroups.com. > > 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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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