On Thu 10-08-17 15:23:05, Colm MacCárthaigh wrote: > On Thu, Aug 10, 2017 at 3:05 PM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: > >> Too late for that. VM_DONTFORK is already implemented > >> through MADV_DONTFORK & MADV_DOFORK, in a way that is > >> very similar to the MADV_WIPEONFORK from these patches. > > > > Yeah, those two seem to be breaking the "madvise as an advise" semantic as > > well but that doesn't mean we should follow that pattern any further. > > I would imagine that many of the crypto applications using > MADV_WIPEONFORK will also be using MADV_DONTDUMP. In cases where it's > for protecting secret keys, I'd like to use both in my code, for > example. Though that doesn't really help decide this. > > There is also at least one case for being able to turn WIPEONFORK > on/off with an existing page; a process that uses privilege separation > often goes through the following flow: > > 1. [ Access privileged keys as a power user and initialize memory ] > 2. [ Fork a child process that actually does the work ] > 3. [ Child drops privileges and uses the memory to do work ] > 4. [ Parent hangs around to re-spawn a child if it crashes ] > > In that mode it would be convenient to be able to mark the memory as > WIPEONFORK in the child, but not the parent. I am not sure I understand. The child will have an own VMA so chaging the attribute will not affect parent. Or did I misunderstand your example? -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
