|6||6||The 0xdeadbeef in the panics here implies that someone is freeing kernel memory that's still in use/referenced somewhere. The main difference when cdda is invoked via userlandfs rather than via the kernel directly is that most of the meat of cdda runs in userland. However, userlandfs must still forward all of the kernel/VFS interactions back and forth (i.e. when the ripper requests to open a file, read a block, etc.). As such, there are two likely possibilities here. Either 1) cdda isn't doing some bookkeeping correctly when it interacts with the VFS, such as calling put_vnode() in a case where it shouldn't, or 2) the way cdda is interacting with the VFS is triggering a corner case/bug in the VFS itself. An outside edge case is that it could also be an issue with the ATAPI code, but that would suggest a similar problem could be triggered with data CDs, which to my knowledge has not been reported to be the case, so that one seems less likely.