From: Peter Zijlstra <peterz@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
John Dias <joaodias@google.com>, Min Chong <mchong@google.com>
Subject: Re: [PATCH] perf: protect group_leader from races that cause ctx
Date: Fri, 6 Jan 2017 10:32:51 +0100 [thread overview]
Message-ID: <20170106093251.GL3093@worktop> (raw)
In-Reply-To: <20170105231429.GA83592@beast>
On Thu, Jan 05, 2017 at 03:14:29PM -0800, Kees Cook wrote:
> From: John Dias <joaodias@google.com>
>
> When moving a group_leader perf event from a software-context to
> a hardware-context, there's a race in checking and updating that
> context. The existing locking solution doesn't work; note that it tries
> to grab a lock inside the group_leader's context object, which you can
> only get at by going through a pointer that should be protected from these
> races. If two threads trigger this operation simultaneously, the refcount
> of 'perf_event_context' will fall to zero and the object may be freed.
>
> To avoid that problem, and to produce a simple solution, we can just
> use a lock per group_leader to protect all checks on the group_leader's
> context. The new lock is grabbed and released when no context locks are
> held.
This Changelog really stinks. I'll go try and reverse engineer the thing
:-(
next prev parent reply other threads:[~2017-01-06 9:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-05 23:14 [PATCH] perf: protect group_leader from races that cause ctx Kees Cook
2017-01-06 9:32 ` Peter Zijlstra [this message]
2017-01-06 13:14 ` Peter Zijlstra
2017-01-06 20:39 ` Kees Cook
2017-01-07 16:29 ` John Dias
2017-01-09 23:16 ` Kees Cook
2017-01-10 8:46 ` Peter Zijlstra
2017-01-10 10:16 ` Ingo Molnar
2017-01-10 23:54 ` Kees Cook
2017-01-14 12:28 ` [tip:perf/urgent] perf/core: Fix concurrent sys_perf_event_open() vs. 'move_group' race tip-bot for Peter Zijlstra
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=20170106093251.GL3093@worktop \
--to=peterz@infradead.org \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=joaodias@google.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mchong@google.com \
--cc=mingo@redhat.com \
/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.