Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg dumps"

From	Kees Cook <keescook@chromium.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg dumps"
Date	2017-08-18 01:10 +0200
Message-ID	<ufC5j-3fa-1@gated-at.bofh.it> (permalink)
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On Wed, Aug 16, 2017 at 6:29 PM, Sergey Senozhatsky
<sergey.senozhatsky.work@gmail.com> wrote:
> can we accidentally "leak" kernel pointers or some other critical
> info? kptr_restrict requires CAP_SYSLOG and pstore read used to
> require CAP_SYSLOG, but it seems that now we can bypass it by
> letting "entirely unprivileged groups" to read pstore. is there
> something to be concerned about (or at least mention it in the
> commit messages)?

I can expand the commit message a bit more, sure. There may be
sensitive things in pstorefs, and it's up to a system builder to
decide how they want to deal with that risk. Most users of pstore
don't mount with update_ms=N so pstorefs contains (mostly) old
addresses. Without this change, though, a builder can't give
permissions to an unprivileged crash dump process without also giving
it CAP_SYSLOG which has much MORE privilege that it would need
(reading and wiping _current_ dmesg, for example).

-Kees

-- 
Kees Cook
Pixel Security

Thread

Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg  dumps" Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-16 10:00 +0200
  Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg dumps" Kees Cook <keescook@chromium.org> - 2017-08-16 17:40 +0200
    Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg  dumps" Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-17 03:30 +0200
      Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg dumps" Kees Cook <keescook@chromium.org> - 2017-08-18 01:10 +0200
        Re: [PATCH 2/2] Revert "pstore: Honor dmesg_restrict sysctl on dmesg  dumps" Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-18 01:30 +0200

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