On Wed, Sep 11, 2019 at 04:16:36PM +0200, Christian Brauner wrote: > 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: > > > What are the user-visible runtime effects of this bug?
The userspace can set -1 as an exit_signal, and that will break process signalling and reaping. > > > 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. > > Sigh, I spoke to soon... Hm, this is placed in _do_fork(). There's a > chance that this might be visible in legacy clone if anyone passes in an > invalid signal greater than NSIG right now somehow, they'd now get > EINVAL if I'm seeing this right. > > So an alternative might be to only fix this in clone3() only right now > and get this patch into 5.3 to not release clone3() with this bug from > legacy clone duplicated. > And we defer the actual legacy clone fix until after next merge window > having it stew in linux-next for a couple of rcs. Distros often pull in > rcs so if anyone notices a regression for legacy clone we'll know about > it... valid_signal() checks at process exit time when the parent is > supposed to be notifed will catch faulty signals anyway so it's not that > big of a deal. As the patch is written, only copy_clone_args_from_user is touched (which is used only by clone3 and not legacy clone), and the check added replicates legacy clone behaviour: userspace can set 0..CSIGNAL as an exit_signal. Having ability to set exit_signal in NSIG..CSIGNAL renge seems to be a bug, but at least it seems to be harmless one and indeed may be addressed separately in the future.
