linux-kernel - Re: [PATCH v2 1/7] modules: Create rlimit for module space

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <657e6d0ada18e8ca0350bc6b3a80c49b3c0b341c.camel@intel.com>
Date:   Sat, 13 Oct 2018 00:04:14 +0000
From:   "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To:     "jannh@...gle.com" <jannh@...gle.com>
CC:     "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "jeyu@...nel.org" <jeyu@...nel.org>,
        "arjan@...ux.intel.com" <arjan@...ux.intel.com>,
        "linux-mips@...ux-mips.org" <linux-mips@...ux-mips.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "kristen@...ux.intel.com" <kristen@...ux.intel.com>,
        "Dock, Deneen T" <deneen.t.dock@...el.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "will.deacon@....com" <will.deacon@....com>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>
Subject: Re: [PATCH v2 1/7] modules: Create rlimit for module space

On Fri, 2018-10-12 at 19:22 +0200, Jann Horn wrote:
> On Fri, Oct 12, 2018 at 7:04 PM Edgecombe, Rick P
> <rick.p.edgecombe@...el.com> wrote:
> > On Fri, 2018-10-12 at 02:35 +0200, Jann Horn wrote:
> > > Why all the rbtree stuff instead of stashing a pointer in struct
> > > vmap_area, or something like that?
> > 
> > Since the tracking was not for all vmalloc usage, the intention was to not
> > bloat
> > the structure for other usages likes stacks. I thought usually there
> > wouldn't be
> > nearly as much module space allocations as there would be kernel stacks, but
> > I
> > didn't do any actual measurements on the tradeoffs.
> 
> I imagine that one extra pointer in there - pointing to your struct
> mod_alloc_user - would probably not be terrible. 8 bytes more per
> kernel stack shouldn't be so bad?

I looked into this and it starts to look a little messy. The nommu.c version of
vmalloc doesn't use or expose access to vmap_area or vm_struct. So it starts to
look like a bunch of IFDEFs to remove the rlimit in the nommu case or making a
stand in that maintains pretend vm struct's in nommu.c. I had actually
previously tried to at least pull the allocations size from vmalloc structs, but it broke on nommu.

Thought I would check back and see. How important do you think this is?