Date: Wed, 21 Nov 2018 20:12:32 +0200 From: Igor Stoppa <igor.stoppa@...il.com> To: Tycho Andersen <tycho@...ho.ws> Cc: Julian Stecklina <jsteckli@...zon.de>, kernel-hardening@...ts.openwall.com, Liran Alon <liran.alon@...cle.com>, Jonathan Adams <jwadams@...gle.com>, David Woodhouse <dwmw2@...radead.org> Subject: Re: [RFC PATCH 0/6] Process-local memory allocations On 21/11/2018 19:48, Tycho Andersen wrote: > On Wed, Nov 21, 2018 at 07:18:17PM +0200, Igor Stoppa wrote: >> Hi, >> >> On 21/11/2018 01:26, Tycho Andersen wrote: [...] >>> This seems similar in spirit to prmem: >>> https://email@example.com/T/#u >>> >>> Basically, we have some special memory that we want to leave unmapped >>> (read only) most of the time, but map it (writable) sometimes. I >>> wonder if we should merge the APIs in to one >>> >>> spmemalloc(size, flags, PRLOCAL) >>> >>> type thing? Could we share some infrastructure then? >> >> For what I can understand from the intro only, this seems to focus on >> "local" information, related to processes, while prmem was mostly aimed, at >> least at this stage, at system-level features, like LSM or SELinux. >> Those have probably little value, for protection from reading. >> And they are used quite often, typically on a critical path. >> The main thing is to prevent rogue writes, but reads are not a problem. >> Hiding/unhiding them even from read operations might not be so useful. >> >> However other components, like the kernel keyring, are used less frequently >> and might be worth protecting them even from read operations. > > Right, the goals are different, but the idea is basically the same. We > allocate memory in some "special" way. I'm just wondering if we'll be > adding more of these special ways in the future, and if it's worth > synchronizing the APIs so that it's easy for people to use. Yes, I agree. I do not see much use for this "locality" in most of the use cases that I have looked into, apart from maybe the kernel keyring, but it might be possible to add a "scope" property to a memory pool, if it is associated to some very specific code. Doing it for system-level components, however, might introduce too big an overhead. In these cases, the scope would stay global. But I really need to see the code, before I can say more. -- igor
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