On Wed, Sep 11, 2019 at 03:52:36PM +0200, Christian Brauner wrote: > On Wed, Sep 11, 2019 at 06:48:52AM -0700, Andrew Morton wrote: > > 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? > > No, as I said in my other mail clone3() is not in any released kernel > yet. clone3() is going to be released in v5.3.
Applied yesteday. This is now fixed and included in mainline. Thanks! Christian
