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.)

kernel.org https://git.kernel.org/stable/c/0d74fd54db0bd0c0c224bef0da8fc95ea9c9f36c [No types assigned]

kernel.org https://git.kernel.org/stable/c/16896914bace82d7811c62f3b6d5320132384f49 [No types assigned]

kernel.org https://git.kernel.org/stable/c/39705a6c29f8a2b93cf5b99528a55366c50014d1 [No types assigned]

kernel.org https://git.kernel.org/stable/c/b14cc2cf313bd29056fadbc8ecd7f957cf5791ff [No types assigned]