CVE-2024-42318 Information

Description

In the Linux kernel the following vulnerability has been resolved:

landlock: Don’t lose track of restrictions on cred_transfer

When a process’ cred struct is replaced this almost always invokes the cred_prepare LSM hook; but in one special case (when KEYCTL_SESSION_TO_PARENT updates the parent’s credentials) the cred_transfer LSM hook is used instead. Landlock only implements the cred_prepare hook not cred_transfer so KEYCTL_SESSION_TO_PARENT causes all information on Landlock restrictions to be lost.

This basically means that a process with the ability to use the fork() and keyctl() syscalls can get rid of all Landlock restrictions on itself.

Fix it by adding a cred_transfer hook that does the same thing as the existing cred_prepare hook. (Implemented by having hook_cred_prepare() call hook_cred_transfer() so that the two functions are less likely to accidentally diverge in the future.)

Reference

https://git.kernel.org/stable/c/0d74fd54db0bd0c0c224bef0da8fc95ea9c9f36c https://git.kernel.org/stable/c/16896914bace82d7811c62f3b6d5320132384f49 https://git.kernel.org/stable/c/b14cc2cf313bd29056fadbc8ecd7f957cf5791ff https://git.kernel.org/stable/c/39705a6c29f8a2b93cf5b99528a55366c50014d1 https://lore.kernel.org/all/20240817.shahka3Ee1iy@digikod.net/