"Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx> writes: > On 09/10/2023 14:37, Kees Cook wrote: >> On Fri, Oct 06, 2023 at 02:07:16PM +0200, David Hildenbrand wrote: >>> On 07.09.23 22:24, Guilherme G. Piccoli wrote: >>>> Currently the kernel provides a symlink to the executable binary, in the >>>> form of procfs file exe_file (/proc/self/exe_file for example). But what >>>> happens in interpreted scenarios (like binfmt_misc) is that such link >>>> always points to the *interpreter*. For cases of Linux binary emulators, >>>> like FEX [0] for example, it's then necessary to somehow mask that and >>>> emulate the true binary path. >>> >>> I'm absolutely no expert on that, but I'm wondering if, instead of modifying >>> exe_file and adding an interpreter file, you'd want to leave exe_file alone >>> and instead provide an easier way to obtain the interpreted file. >>> >>> Can you maybe describe why modifying exe_file is desired (about which >>> consumers are we worrying? ) and what exactly FEX does to handle that (how >>> does it mask that?). >>> >>> So a bit more background on the challenges without this change would be >>> appreciated. >> >> Yeah, it sounds like you're dealing with a process that examines >> /proc/self/exe_file for itself only to find the binfmt_misc interpreter >> when it was run via binfmt_misc? >> >> What actually breaks? Or rather, why does the process to examine >> exe_file? I'm just trying to see if there are other solutions here that >> would avoid creating an ambiguous interface... >> > > Thanks Kees and David! Did Ryan's thorough comment addressed your > questions? Do you have any take on the TODOs? > > I can maybe rebase against 6.7-rc1 and resubmit , if that makes sense! > But would be better having the TODOs addressed, I guess. Currently there is a mechanism in the kernel for changing /proc/self/exe. Would that be reasonable to use in this case? It came from the checkpoint/restart work, but given that it is already implemented it seems like the path of least resistance to get your binfmt_misc that wants to look like binfmt_elf to use that mechanism. Eric
