linux-kernel - Re: [PATCH v3 1/2] mm/page_idle: Add per-pid idle page tracking using virtual indexing

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: <CAEXW_YQN+htU-LpYQ_jxepVdRhO0byw1pWFrsbU2XsH=8FDKLA@mail.gmail.com>
Date:   Tue, 30 Jul 2019 09:06:36 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brendan Gregg <bgregg@...flix.com>,
        Christian Hansen <chansen3@...co.com>,
        Daniel Colascione <dancol@...gle.com>,
        Florian Mayer <fmayer@...gle.com>,
        John Dias <joaodias@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        kernel-team <kernel-team@...roid.com>,
        Linux API <linux-api@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux FS Devel <linux-fsdevel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>, Michal Hocko <mhocko@...e.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Minchan Kim <minchan@...nel.org>,
        Namhyung Kim <namhyung@...gle.com>,
        Roman Gushchin <guro@...com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>, Wei Wang <wvw@...gle.com>
Subject: Re: [PATCH v3 1/2] mm/page_idle: Add per-pid idle page tracking using
 virtual indexing

On Fri, Jul 26, 2019 at 11:23 AM Joel Fernandes (Google)
<joel@...lfernandes.org> wrote:
>
> The page_idle tracking feature currently requires looking up the pagemap
> for a process followed by interacting with /sys/kernel/mm/page_idle.
> Looking up PFN from pagemap in Android devices is not supported by
> unprivileged process and requires SYS_ADMIN and gives 0 for the PFN.
>
> This patch adds support to directly interact with page_idle tracking at
> the PID level by introducing a /proc/<pid>/page_idle file.  It follows
> the exact same semantics as the global /sys/kernel/mm/page_idle, but now
> looking up PFN through pagemap is not needed since the interface uses
> virtual frame numbers, and at the same time also does not require
> SYS_ADMIN.
>
> In Android, we are using this for the heap profiler (heapprofd) which
> profiles and pin points code paths which allocates and leaves memory
> idle for long periods of time. This method solves the security issue
> with userspace learning the PFN, and while at it is also shown to yield
> better results than the pagemap lookup, the theory being that the window
> where the address space can change is reduced by eliminating the
> intermediate pagemap look up stage. In virtual address indexing, the
> process's mmap_sem is held for the duration of the access.
>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
>
> ---
> v2->v3:
> Fixed a bug where I was doing a kfree that is not needed due to not
> needing to do GFP_ATOMIC allocations.
>
> v1->v2:
> Mark swap ptes as idle (Minchan)
> Avoid need for GFP_ATOMIC (Andrew)
> Get rid of idle_page_list lock by moving list to stack

I believe all suggestions have been addressed.  Do these look good now?

thanks,

 - Joel



> Internal review -> v1:
> Fixes from Suren.
> Corrections to change log, docs (Florian, Sandeep)
>
>  fs/proc/base.c            |   3 +
>  fs/proc/internal.h        |   1 +
>  fs/proc/task_mmu.c        |  57 +++++++
>  include/linux/page_idle.h |   4 +
>  mm/page_idle.c            | 340 +++++++++++++++++++++++++++++++++-----
>  5 files changed, 360 insertions(+), 45 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 77eb628ecc7f..a58dd74606e9 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -3021,6 +3021,9 @@ static const struct pid_entry tgid_base_stuff[] = {
>         REG("smaps",      S_IRUGO, proc_pid_smaps_operations),
>         REG("smaps_rollup", S_IRUGO, proc_pid_smaps_rollup_operations),