linux-kernel - Re: [PATCH] Uprobes: Fix kernel oops with delayed_uprobe

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Date:   Tue, 4 Dec 2018 00:58:03 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     Oleg Nesterov <oleg@...hat.com>, srikar@...ux.vnet.ibm.com,
        mhiramat@...nel.org, liu.song.a23@...il.com, peterz@...radead.org,
        mingo@...hat.com, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-kernel@...r.kernel.org,
        ananth@...ux.vnet.ibm.com, alexis.berlemont@...il.com,
        naveen.n.rao@...ux.vnet.ibm.com,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
        linux@...linux.org.uk, ralf@...ux-mips.org, paul.burton@...s.com
Subject: Re: [PATCH] Uprobes: Fix kernel oops with delayed_uprobe_remove()

On Mon, 3 Dec 2018 11:52:41 +0530
Ravi Bangoria <ravi.bangoria@...ux.ibm.com> wrote:

> Hi Steve,
> 
> Please pull this patch.
> 

Please send a v2 version of the patch with the updated change log. And
should it have a Fixes and be tagged for stable?

-- Steve

> Thanks.
> 
> On 11/15/18 6:13 PM, Oleg Nesterov wrote:
> > On 11/15, Ravi Bangoria wrote:  
> >>
> >> 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  
> > 
> > Thanks, looks good,
> > 
> > Oleg.
> >