Yes, probably. The lifetimes looked fishy to me to start with, but this might have made things worse. On Tue, Aug 08, 2023 at 05:50:02PM +0200, Christian Brauner wrote: > On Mon, Aug 07, 2023 at 08:24:36PM -0700, syzbot wrote: > > syzbot has bisected this issue to: > > > > commit 066d64b26a21a5b5c500a30f27f3e4b1959aac9e > > Author: Christoph Hellwig <hch@xxxxxx> > > Date: Wed Aug 2 15:41:23 2023 +0000 > > > > btrfs: open block devices after superblock creation > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15493371a80000 > > start commit: f7dc24b34138 Add linux-next specific files for 20230807 > > git tree: linux-next > > final oops: https://syzkaller.appspot.com/x/report.txt?x=17493371a80000 > > console output: https://syzkaller.appspot.com/x/log.txt?x=13493371a80000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=d7847c9dca13d6c5 > > dashboard link: https://syzkaller.appspot.com/bug?extid=26860029a4d562566231 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179704c9a80000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17868ba9a80000 > > > > Reported-by: syzbot+26860029a4d562566231@xxxxxxxxxxxxxxxxxxxxxxxxx > > Fixes: 066d64b26a21 ("btrfs: open block devices after superblock creation") > > > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > > I think the issue might be that before your patch the lifetime of: > @device was aligned with @device->s_fs_info but now that you're dropping > the uuid mutex after btrfs_scan_one_device() that isn't true anymore. So > it feels like: > > P1 P2 > lock_uuid_mutex; > device = btrfs_scan_one_device(); > fs_devices = device->fs_devices; > unlock_uuid_mutex; > // earlier mount that gets cleaned up > lock_uuid_mutex; > btrfs_close_devices(fs_devices); > unlock_uuid_mutex; > > lock_uuid_mutex; > btrfs_open_devices(fs_devices); // UAF > unlock_uuid_mutex; > > But I'm not entirely sure. ---end quoted text---
