> On May 12, 2021, at 10:26 PM, YiFei Zhu <zhuyifei1999@xxxxxxxxx> wrote: > > On Wed, May 12, 2021 at 5:36 PM Alexei Starovoitov > <alexei.starovoitov@xxxxxxxxx> wrote: >> Typically the verifier does all the checks at load time to avoid >> run-time overhead during program execution. Then at attach time we >> check that attach parameters provided at load time match exactly >> to those at attach time. ifindex, attach_btf_id, etc fall into this category. >> Doing something similar it should be possible to avoid >> doing get_dumpable() at run-time. > > Do you mean to move the check of dumpable to load time instead of > runtime? I do not think that makes sense. A process may arbitrarily > set its dumpable attribute during execution via prctl. A process could > do set itself to non-dumpable, before interacting with sensitive > information that would better not be possible to be dumped (eg. > ssh-agent does this [1]). Therefore, being dumpable at one point in > time does not indicate anything about whether it stays dumpable at a > later point in time. Besides, seccomp filters are inherited across > clone and exec, attaching to many tasks with no option to detach. What > should the load-time check of task dump-ability be against? The > current task may only be the tip of an iceburg. > > [1] https://github.com/openssh/openssh-portable/blob/2dc328023f60212cd29504fc05d849133ae47355/ssh-agent.c#L1398 > > First things first: why are you checking dumpable at all? Once you figure out why and whether it’s needed, you may learn something about what task to check. I don’t think checking dumpable makes any sense.
