linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: srikar@linux.vnet.ibm.com, rostedt@goodmis.org,
	mhiramat@kernel.org, liu.song.a23@gmail.com,
	peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
	alexander.shishkin@linux.intel.com, jolsa@redhat.com,
	namhyung@kernel.org, linux-kernel@vger.kernel.org,
	ananth@linux.vnet.ibm.com, alexis.berlemont@gmail.com,
	naveen.n.rao@linux.vnet.ibm.com,
	linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org,
	linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com,
	Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Subject: Re: [PATCH] Uprobes: Fix kernel oops with delayed_uprobe_remove()
Date: Thu, 15 Nov 2018 09:36:42 +0530	[thread overview]
Message-ID: <556c2aa5-550d-d96f-7ed2-549d8f3d803b@linux.ibm.com> (raw)
In-Reply-To: <20181114160600.GD13885@redhat.com>

Hi Oleg,

On 11/14/18 9:36 PM, Oleg Nesterov wrote:
> On 11/14, Ravi Bangoria wrote:
>>
>> syzbot reported a kernel crash with delayed_uprobe_remove():
>>   https://lkml.org/lkml/2018/11/1/1244
>>
>> Backtrace mentioned in the link points to a race between process
>> exit and uprobe_unregister(). Fix it by locking delayed_uprobe_lock
>> before calling delayed_uprobe_remove() from put_uprobe().
> 
> The patch looks good to me, but could you update the changelog?
> 
> Please explain that the exiting task calls uprobe_clear_state() which
> can race with delayed_uprobe_remove(). IIUC this is the only problem
> solved by this patch, right?

Right. Is this better:

There could be a race between task exit and probe unregister:

  exit_mm()
  mmput()
  __mmput()                     uprobe_unregister()
  uprobe_clear_state()          put_uprobe()
  delayed_uprobe_remove()       delayed_uprobe_remove()

put_uprobe() is calling delayed_uprobe_remove() without taking
delayed_uprobe_lock and thus the race sometimes results in a
kernel crash. Fix this by taking delayed_uprobe_lock before
calling delayed_uprobe_remove() from put_uprobe().

Detailed crash log can be found at:
  https://lkml.org/lkml/2018/11/1/1244


  reply	other threads:[~2018-11-15  4:07 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-14  8:19 [PATCH] Uprobes: Fix kernel oops with delayed_uprobe_remove() Ravi Bangoria
2018-11-14 16:06 ` Oleg Nesterov
2018-11-15  4:06   ` Ravi Bangoria [this message]
2018-11-15 12:43     ` Oleg Nesterov
2018-12-03  6:22       ` Ravi Bangoria
2018-12-04  5:58         ` Steven Rostedt
2018-12-05  3:34           ` [PATCH v2] " Ravi Bangoria
2018-12-05 10:01             ` Srikar Dronamraju
2018-12-05 14:39             ` Oleg Nesterov

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=556c2aa5-550d-d96f-7ed2-549d8f3d803b@linux.ibm.com \
    --to=ravi.bangoria@linux.ibm.com \
    --cc=acme@kernel.org \
    --cc=alexander.shishkin@linux.intel.com \
    --cc=alexis.berlemont@gmail.com \
    --cc=ananth@linux.vnet.ibm.com \
    --cc=jolsa@redhat.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mips@linux-mips.org \
    --cc=linux@armlinux.org.uk \
    --cc=liu.song.a23@gmail.com \
    --cc=mhiramat@kernel.org \
    --cc=mingo@redhat.com \
    --cc=namhyung@kernel.org \
    --cc=naveen.n.rao@linux.vnet.ibm.com \
    --cc=oleg@redhat.com \
    --cc=paul.burton@mips.com \
    --cc=peterz@infradead.org \
    --cc=ralf@linux-mips.org \
    --cc=rostedt@goodmis.org \
    --cc=srikar@linux.vnet.ibm.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).