On Mon, Nov 23, 2020 at 10:25:13AM -0800, Linus Torvalds wrote: > On Mon, Nov 23, 2020 at 9:52 AM Oleg Nesterov <oleg@xxxxxxxxxx> wrote: > > > > Can anyone explain why does do_coredump() need unshare_files() at all? > > Hmm. It goes back to 2012, and it's placed just before calling > "->core_dump()", so I assume some core dumping function messed with > the file table back when.. > > I can't see anything like that currently. > > The alternative is that core-dumping just keeps the file table around > for a long while, and thus files don't actually close in a timely > manner. So it might not be a "correctness" issue as much as a latency > issue. IIRC, it was "weird architecture hooks might be playing silly buggers with some per-descriptor information they want in coredumps, better make sure it can't change under them"; it doesn't cost much and it reduced the analysis surface nicely. Had been a while ago, so the memories might be faulty... Anyway, that reasoning seems to be applicable right now - rather than keeping an eye on coredump logics on random architectures that might be looking at descriptor table in unsafe way, just make sure they have a stable private table and be done with that. How much is simplified by not doing it there, anyway?
