On Tue, 10 Sep 2019 18:58:52 +0100 Eugene Syromiatnikov <e...@redhat.com> wrote:
> Previously, higher 32 bits of exit_signal fields were lost when > copied to the kernel args structure (that uses int as a type for the > respective field). Moreover, as Oleg has noted[1], exit_signal is used > unchecked, so it has to be checked for sanity before use; for the legacy > syscalls, applying CSIGNAL mask guarantees that it is at least non-negative; > however, there's no such thing is done in clone3() code path, and that can > break at least thread_group_leader. > > Checking user-passed exit_signal against ~CSIGNAL mask solves both > of these problems. > > [1] https://lkml.org/lkml/2019/9/10/467 > > * kernel/fork.c (copy_clone_args_from_user): Fail with -EINVAL if > args.exit_signal has bits set outside CSIGNAL mask. > (_do_fork): Note that exit_signal is expected to be checked for the > sanity by the caller. > > Fixes: 7f192e3cd316 ("fork: add clone3") What are the user-visible runtime effects of this bug? Relatedly, should this fix be backported into -stable kernels? If so, why?
