linux-kernel - Re: Prevent inconsistent CPU state after sequence of dlclose/dlopen

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: <20250110171112.GF4213@noisy.programming.kicks-ass.net>
Date: Fri, 10 Jan 2025 18:11:12 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: libc-alpha <libc-alpha@...rceware.org>,
	Florian Weimer <fweimer@...hat.com>,
	"carlos@...hat.com" <carlos@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86@...nel.org,
	paulmck <paulmck@...nel.org>,
	Michael Jeanson <mjeanson@...icios.com>
Subject: Re: Prevent inconsistent CPU state after sequence of dlclose/dlopen

On Fri, Jan 10, 2025 at 12:02:27PM -0500, Mathieu Desnoyers wrote:
> On 2025-01-10 11:54, Peter Zijlstra wrote:
> > On Fri, Jan 10, 2025 at 10:55:36AM -0500, Mathieu Desnoyers wrote:
> > > Hi,
> > > 
> > > I was discussing with Mark Rutland recently, and he pointed out that a
> > > sequence of dlclose/dlopen mapping new code at the same addresses in
> > > multithreaded environments is an issue on ARM, and possibly on Intel/AMD
> > > with the newer TLB broadcast maintenance.
> > 
> > What is the exact race? Should not munmap() invalidate the TLBs before
> > it allows overlapping mmap() to complete?
> 
> The race Mark mentioned (on ARM) is AFAIU the following scenario:
> 
> CPU 0                     CPU 1
> 
> - dlopen()
>   - mmap PROT_EXEC @addr
>                           - fetch insn @addr, CPU state expects unchanged insn.
>                           - execute unrelated code
> - dlclose(addr)
>   - munmap @addr
> - dlopen()
>   - mmap PROT_EXEC @addr
>                           - fetch new insn @addr. Incoherent CPU state.

Urgh.. Mark, is this because of non-coherent i-cache or somesuch misery?

But shouldn't flush_{,i}cache_range() or something along those lines not
handle this?