search

containers / libkrun

A dynamic library providing Virtualization-based process isolation capabilities
Apache License 2.0
898 stars 74 forks source link

Out of range slice panic for `init` virtio reads. #136

Closed Reisen closed 1 year ago

Reisen commented 1 year ago

I'm testing out libkrun with podman and ran into the following error:

$ podman run --runtime=/usr/local/bin/krun --rm docker.io/hello-world
panicked at 'range end index 733184 out of range for slice of length 732776', src/devices/src/virtio/fs/linux/passthrough.rs:987:29

Which I noticed 732776 is the size of my init binary. Indeed this seems to happen specifically when the read is detected against the init file's inode.

I believe this may be related to this check in setupmapping? Which I'm guessing would normally lead to a SIGBUS error when trying to read beyond the end of a partially filled page. I worked around this by padding my init with 0's:

truncate -s 733184 init/init

This does work, but it is a bit of a nasty hack. I'm guessing the main cause here is an off by one page mapping bug of some kind but I am not familiar at all with virtio/fuse so I'm making wild guesses, but it happens with the standard suggested build process.

EDIT:

Just spotted #132 -- I'm assuming this is related, just for context this is happening on master for me, my page size for reference:

$ getconf PAGESIZE
4096
slp commented 1 year ago

Thanks for the report! There was a bug in that piece of code. Userspace may request to read beyond the end of the file, and we must return as many bytes as possible. Could you please check if #138 fixes the problem for you?