On Tue May 21, 2024 at 5:29 PM EEST, Tycho Andersen wrote: > On Tue, May 21, 2024 at 01:12:57AM +0300, Jarkko Sakkinen wrote: > > On Tue May 21, 2024 at 12:13 AM EEST, Tycho Andersen wrote: > > > On Mon, May 20, 2024 at 12:25:27PM -0700, Jonathan Calmels wrote: > > > > On Mon, May 20, 2024 at 07:30:14AM GMT, Tycho Andersen wrote: > > > > > there is an ongoing effort (started at [0]) to constify the first arg > > > > > here, since you're not supposed to write to it. Your usage looks > > > > > correct to me, so I think all it needs is a literal "const" here. > > > > > > > > Will do, along with the suggestions from Jarkko > > > > > > > > > > + struct ctl_table t; > > > > > > + unsigned long mask_array[2]; > > > > > > + kernel_cap_t new_mask, *mask; > > > > > > + int err; > > > > > > + > > > > > > + if (write && (!capable(CAP_SETPCAP) || > > > > > > + !capable(CAP_SYS_ADMIN))) > > > > > > + return -EPERM; > > > > > > > > > > ...why CAP_SYS_ADMIN? You mention it in the changelog, but don't > > > > > explain why. > > > > > > > > No reason really, I was hoping we could decide what we want here. > > > > UMH uses CAP_SYS_MODULE, Serge mentioned adding a new cap maybe. > > > > > > I don't have a strong preference between SETPCAP and a new capability, > > > but I do think it should be just one. SYS_ADMIN is already god mode > > > enough, IMO. > > > > Sometimes I think would it make more sense to invent something > > completely new like capabilities but more modern and robust, instead of > > increasing complexity of a broken mechanism (especially thanks to > > CAP_MAC_ADMIN). > > > > I kind of liked the idea of privilege tokens both in Symbian and Maemo > > (have been involved professionally in both). Emphasis on the idea not > > necessarily on implementation. > > > > Not an LSM but like something that you could use in the place of POSIX > > caps. Probably quite tedious effort tho because you would need to pull > > the whole industry with the new thing... > > And then we have LSM hooks, (ns_)capable(), __secure_computing() plus > a new set of hooks for this new thing sprinkled around. I guess > kernel developers wouldn't be excited about it, let alone the rest of > the industry :) > > Thinking out loud: I wonder if fixing the seccomp TOCTOU against > pointers would help here. I guess you'd still have issues where your > policy engine resolves a path arg to open() and that inode changes > between the decision and the actual vfs access, you have just changed > the TOCTOU. > > Or even scarier: what if you could change the return value at any > kprobe? :) I had one crazy idea related to seccomp filters once. What if there was way to compose tokens that would be just a seccomp filter like the one that you pass to PR_SET_SECCOMP but presented with a file descriptor? Then you could send these with SCM_RIGHTS to other processes and they could upgrade their existing filter with them. So it would be a kind of extension mechanism for a seccomp filter. Not something I'm seriously suggesting but though to flush this out now that we are on these topics anyhow ;-) > Tycho PS. Sorry if my language was a bit harsh earlier but I think I had also a point related to at least to the patch set presentation. I.e. you are very precise describing the mechanism but motivation and bringing topic somehow to a context is equally important :-) BR, Jarkko
