linux-kernel - Re: [PATCH] perf: Fix oops when kthread execs user process

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190529161955.GZ2623@hirez.programming.kicks-ass.net>
Date:   Wed, 29 May 2019 18:19:55 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Will Deacon <will.deacon@....com>
Cc:     Young Xiao <92siuyang@...il.com>, linux@...linux.org.uk,
        mark.rutland@....com, mingo@...hat.com, bp@...en8.de,
        hpa@...or.com, x86@...nel.org, kan.liang@...ux.intel.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        ravi.bangoria@...ux.vnet.ibm.com, mpe@...erman.id.au,
        acme@...hat.com, eranian@...gle.com, fweisbec@...il.com,
        jolsa@...hat.com
Subject: Re: [PATCH] perf: Fix oops when kthread execs user process

On Wed, May 29, 2019 at 03:35:10PM +0100, Will Deacon wrote:
> On Wed, May 29, 2019 at 03:25:15PM +0200, Peter Zijlstra wrote:
> > On Wed, May 29, 2019 at 02:05:21PM +0100, Will Deacon wrote:
> > > On Wed, May 29, 2019 at 02:55:57PM +0200, Peter Zijlstra wrote:
> > 
> > > >  	if (user_mode(regs)) {
> > > 
> > > Hmm, so it just occurred to me that Mark's observation is that the regs
> > > can be junk in some cases. In which case, should we be checking for
> > > kthreads first?
> > 
> > task_pt_regs() can return garbage, but @regs is the exception (or
> > perf_arch_fetch_caller_regs()) regs, and for those user_mode() had
> > better be correct.
> 
> So what should we report for the idle task?

If an interrupt hits the idle task, @regs would be !user_mode(regs),
we'll find current->flags & PF_KTHREAD (idle not having passed through
exec()) and therefore we'll take ABI_NONE for the user regs.

Or am I not getting it?