Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
liveupdate: validate session type before performing operation
The sessions ioctls are not applicable to all session types. PRESERVE_FD is only applicable to outgoing sessions. RETRIEVE_FD and FINISH are only valid for incoming session. Calling a incoming ioctl on an outgoing session is invalid and can cause file handlers to run into unexpected errors.
For example, a user can create a (outgoing) session, preserve a memfd, and then immediately do a retrieve without doing a kexec in between. This would result in memfd’s retrieve handler to run. The handlers expects to be called from a post-kexec context, and will try to do a kho_restore_vmalloc() or kho_restore_folio() to try and restore memory.
KHO catches this (thanks to KHO_PAGE_MAGIC) and returns an error, but since this is considered an internal error and KHO throws out a bunch of WARN()s.
Associate a type with each ioctl op and validate the type in luo_session_ioctl() before dispatching the ioctl handler to make sure the op is being called for the right session type.
Details
- Affected product:
- Debian 10 ELS
- Affected packages:
- linux @ 4.19.0