From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@elte.hu>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anton Arapov <anton@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] uprobes: write_opcode()->__replace_page() can race with try_to_unmap()
Date: Fri, 08 Jun 2012 10:47:07 +0200 [thread overview]
Message-ID: <1339145227.23343.42.camel@twins> (raw)
In-Reply-To: <20120607170041.GC31974@redhat.com>
On Thu, 2012-06-07 at 19:00 +0200, Oleg Nesterov wrote:
> write_opcode() gets old_page via get_user_pages() and then calls
> __replace_page() which assumes that this old_page is still mapped
> after pte_offset_map_lock().
>
> This is not true if this old_page was already try_to_unmap()'ed,
> and in this case everything __replace_page() does with old_page
> is wrong. Just for example, put_page() is not balanced.
>
> I think it is possible to teach __replace_page() to handle this
> unlikely case correctly, but this patch simply changes it to use
> page_check_address() and return -EAGAIN if it fails. The caller
> should notice this error code and retry.
Note that replace_page() was nicked from ksm, does that suffer a similar
problem?
next prev parent reply other threads:[~2012-06-08 8:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-07 16:59 [PATCH 0/3] uprobes fixes for 3.5 Oleg Nesterov
2012-06-07 17:00 ` [PATCH 1/3] uprobes: valid_vma() should reject VM_HUGETLB Oleg Nesterov
2012-06-15 6:22 ` Srikar Dronamraju
2012-06-07 17:00 ` [PATCH 2/3] uprobes: __copy_insn() should ensure a_ops->readpage != NULL Oleg Nesterov
2012-06-15 6:25 ` Srikar Dronamraju
2012-06-15 12:10 ` Ingo Molnar
2012-06-07 17:00 ` [PATCH 3/3] uprobes: write_opcode()->__replace_page() can race with try_to_unmap() Oleg Nesterov
2012-06-08 8:47 ` Peter Zijlstra [this message]
2012-06-08 10:03 ` Oleg Nesterov
2012-06-08 16:55 ` Oleg Nesterov
2012-06-15 6:12 ` Srikar Dronamraju
2012-06-15 12:11 ` Ingo Molnar
2012-06-15 15:48 ` Oleg Nesterov
2012-06-16 7:11 ` Ingo Molnar
2012-06-08 14:03 ` oom-killer is crazy? (Was: [PATCH 0/3] uprobes fixes for 3.5) Oleg Nesterov
2012-06-08 14:26 ` Dave Jones
2012-06-08 15:04 ` Oleg Nesterov
2012-06-08 20:21 ` [patch for-3.5-rc1] mm, oom: fix badness score underflow David Rientjes
2012-06-09 22:25 ` KOSAKI Motohiro
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1339145227.23343.42.camel@twins \
--to=peterz@infradead.org \
--cc=ananth@in.ibm.com \
--cc=anton@redhat.com \
--cc=hughd@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=masami.hiramatsu.pt@hitachi.com \
--cc=mingo@elte.hu \
--cc=oleg@redhat.com \
--cc=srikar@linux.vnet.ibm.com \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.