On Wed 09-12-20 14:38:42, Jan Kara wrote: > Hello! > > so I was debugging the dnotify crash below (it's 100% reproducible for me) > and I came to the following. The reproducer opens 'file0' on FUSE > filesystem which is a directory at that point. Then it attached dnotify > mark to the directory 'file0' and then it does something to the FUSE fs > which I don't understand but the result is that when FUSE is unmounted the > 'file0' inode is actually a regular file (note that I've verified this is > really the same inode pointer). This then confuses dnotify which doesn't > tear down its structures properly and eventually crashes. So my question > is: How can an inode on FUSE filesystem morph from a dir to a regular file? > I presume this could confuse much more things than just dnotify? > > Before I dwelve more into FUSE internals, any idea Miklos what could have > gone wrong and how to debug this further? I've got an idea where to look and indeed it is the fuse_do_getattr() call that finds attributes returned by the server are inconsistent so it calls make_bad_inode() which, among other things, does: inode->i_mode = S_IFREG; Indeed calling make_bad_inode() on a live inode doesn't look like a good idea. IMHO FUSE needs to come up with some other means of marking the inode as stale. Miklos? Honza > On Mon 23-11-20 02:05:16, syzbot wrote: > > syzbot found the following issue on: > > > > HEAD commit: 27bba9c5 Merge tag 'scsi-fixes' of git://git.kernel.org/pu.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=11b82225500000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=330f3436df12fd44 > > dashboard link: https://syzkaller.appspot.com/bug?extid=f427adf9324b92652ccc > > compiler: gcc (GCC) 10.1.0-syz 20200507 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11d3f015500000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17162d4d500000 > > > > Bisection is inconclusive: the issue happens on the oldest tested release. > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16570525500000 > > final oops: https://syzkaller.appspot.com/x/report.txt?x=15570525500000 > > console output: https://syzkaller.appspot.com/x/log.txt?x=11570525500000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+f427adf9324b92652ccc@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50 > > ------------[ cut here ]------------ > > kernel BUG at fs/notify/dnotify/dnotify.c:118! > > invalid opcode: 0000 [#1] PREEMPT SMP KASAN > > CPU: 1 PID: 648 Comm: kworker/u4:4 Not tainted 5.10.0-rc4-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Workqueue: events_unbound fsnotify_mark_destroy_workfn > > RIP: 0010:dnotify_free_mark fs/notify/dnotify/dnotify.c:118 [inline] > > RIP: 0010:dnotify_free_mark+0x4b/0x60 fs/notify/dnotify/dnotify.c:112 > > Code: 80 3c 02 00 75 26 48 83 bd 80 00 00 00 00 75 15 e8 0a d3 a0 ff 48 89 ee 48 8b 3d 68 8c 1d 0b 5d e9 aa 06 e2 ff e8 f5 d2 a0 ff <0f> 0b e8 ae 4d e2 ff eb d3 66 90 66 2e 0f 1f 84 00 00 00 00 00 41 > > RSP: 0018:ffffc90002f1fc38 EFLAGS: 00010293 > > RAX: 0000000000000000 RBX: ffffffff8958ae60 RCX: 1ffff920005e3f95 > > RDX: ffff888012601a40 RSI: ffffffff81cf5ceb RDI: ffff88801aea2080 > > RBP: ffff88801aea2000 R08: 0000000000000001 R09: ffffffff8ebb170f > > R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880171a2000 > > R13: ffffc90002f1fc98 R14: ffff88801aea2010 R15: ffff88801aea2018 > > FS: 0000000000000000(0000) GS:ffff8880b9f00000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 000056045fa95978 CR3: 0000000012121000 CR4: 00000000001506e0 > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Call Trace: > > fsnotify_final_mark_destroy+0x71/0xb0 fs/notify/mark.c:205 > > fsnotify_mark_destroy_workfn+0x1eb/0x340 fs/notify/mark.c:840 > > process_one_work+0x933/0x15a0 kernel/workqueue.c:2272 > > worker_thread+0x64c/0x1120 kernel/workqueue.c:2418 > > kthread+0x3af/0x4a0 kernel/kthread.c:292 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 > > Modules linked in: > > > > > > --- > > This report 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 issue. 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 issue, for details see: > > https://goo.gl/tpsmEJ#testing-patches > -- > Jan Kara <jack@xxxxxxxx> > SUSE Labs, CR -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
