From: Colin Cross <ccross@google.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: "Matthew Wilcox" <willy@infradead.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
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Subject: Re: [PATCH v7 3/3] mm: add a field to store names for private anonymous memory
Date: Thu, 3 Sep 2020 08:59:38 -0700 [thread overview]
Message-ID: <CAMbhsRSxKd-tj2q4a1eDfavdPyKBDCKG_F4x55zYKBUceu_ruA@mail.gmail.com> (raw)
In-Reply-To: <20200903135806.ceoivs5pzlchg6uj@black.fi.intel.com>
On Thu, Sep 3, 2020 at 6:58 AM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Thu, Sep 03, 2020 at 02:43:40PM +0100, Matthew Wilcox wrote:
> > On Thu, Sep 03, 2020 at 04:25:37PM +0300, Kirill A. Shutemov wrote:
> > > IIUC, it gives userspace direct control of content of /proc/$PID/maps and
> > > /proc/$PID/smaps. There's no verification of the given string whatsoever.
> > > I'm sure security experts would find clever usage of the feature :P
> >
> > What, you think that naming a VMA
> > "\n55bc3e0f9000-55bc3e0fb000 r--p 00000000 fd:01 16777285 /bin/cat" might cause problems?
The data is wrapped inside "[anon: ]", which limits the ability to
masquerade as a real file.
> Something that would cause buffer overrun or out-of-bound access in a
> privilaged parser can be even more interesting. :)
This is the same as /proc/pid/cmdline, which has no sanitization.
It's also limited to 255 bytes, which should hopefully limit the
opportunity for a buffer overrun.
> > Would it be enough to restrict the characters to isalnum()?
>
> I guess.
>
> But current design stores userspace pointer and there's time-of-check vs.
> time-of-use problem.
It copies from userspace into a kernel buffer at read time, any
desired sanitization could easily be added there.
> --
> Kirill A. Shutemov
>
next prev parent reply other threads:[~2020-09-03 15:59 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 16:14 [PATCH v7 0/3] Anonymous VMA naming patches Sumit Semwal
2020-09-01 16:14 ` [PATCH v7 1/3] mm: rearrange madvise code to allow for reuse Sumit Semwal
2020-09-01 16:14 ` [PATCH v7 2/3] mm: memory: Add access_remote_vm_locked variant Sumit Semwal
2020-09-01 16:14 ` [PATCH v7 3/3] mm: add a field to store names for private anonymous memory Sumit Semwal
2020-09-03 13:25 ` Kirill A. Shutemov
2020-09-03 13:43 ` Matthew Wilcox
2020-09-03 13:58 ` Kirill A. Shutemov
2020-09-03 15:59 ` Colin Cross [this message]
2020-09-03 17:31 ` Kees Cook
2020-09-03 17:54 ` Colin Cross
2020-09-03 18:00 ` Dave Hansen
2020-09-03 18:00 ` Kees Cook
2020-09-03 18:09 ` Dave Hansen
2020-09-03 18:26 ` Colin Cross
2020-09-03 18:40 ` Dave Hansen
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