linux-kernel - Re: [paulmck-rcu:dev.2025.08.13a] [tracing] 364ac25d46: WARNING:at_arch/x86/mm/fault.c:#do_user_addr

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: <d1ee722b-eb90-4b7e-9c2f-2db7d3b33ce9@paulmck-laptop>
Date: Wed, 3 Sep 2025 03:31:31 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Oliver Sang <oliver.sang@...el.com>
Cc: oe-lkp@...ts.linux.dev, lkp@...el.com, linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-trace-kernel@...r.kernel.org
Subject: Re: [paulmck-rcu:dev.2025.08.13a] [tracing]  364ac25d46:
 WARNING:at_arch/x86/mm/fault.c:#do_user_addr_fault

On Wed, Sep 03, 2025 at 09:34:38AM +0800, Oliver Sang wrote:
> hi, Paul,
> 
> On Fri, Aug 29, 2025 at 08:07:41AM -0700, Paul E. McKenney wrote:
> > On Thu, Aug 21, 2025 at 01:26:45PM +0800, kernel test robot wrote:
> > > 
> > > hi, Paul,
> > > 
> > > we also noticed there is similar commit in newer branch
> > >   dev.2025.08.14a
> > >   dev.2025.08.19a
> > > but we didn't finish any bisect for them so far.
> > > 
> > > if the issue is already known and fixed in newer version, please just ignore
> > > this report. sorry if any inconvenience.
> > > 
> > > below full report FYI.
> > > 
> > > 
> > > Hello,
> > > 
> > > kernel test robot noticed "WARNING:at_arch/x86/mm/fault.c:#do_user_addr_fault" on:
> > > 
> > > commit: 364ac25d46eea504eb90229d2a1f92e18c1a1eae ("tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast")
> > > https://git.kernel.org/cgit/linux/kernel/git/paulmck/linux-rcu.git dev.2025.08.13a
> > > 
> > > in testcase: boot
> > > 
> > > config: i386-randconfig-004-20250819
> > > compiler: clang-20
> > > test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G
> > > 
> > > (please refer to attached dmesg/kmsg for entire log/backtrace)
> > 
> > Thank you for your testing efforts, and apologies for being slow!
> > 
> > Could you please try the diagnostic patch at the end of this email?
> > 
> > 							Thanx, Paul
> 
> by applying the patch, the issue gone. but since you said this is a 'diagnostic
> patch', not sure if it's a real fix. anyway:
> 
> Tested-by: kernel test robot <oliver.sang@...el.com>

Thank you very much!  This tells me that something on the code path from
the tracepoint to the BPF program needs to have preemption disabled.
I will leave the diagnostic patch in my tree, and will be looking into
what the real fix should be.

							Thanx, Paul

> [...]
> 
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <oliver.sang@...el.com>
> > > | Closes: https://lore.kernel.org/oe-lkp/202508211038.c93e8603-lkp@intel.com
> 
> [...]
> 
> > > The kernel config and materials to reproduce are available at:
> > > https://download.01.org/0day-ci/archive/20250821/202508211038.c93e8603-lkp@intel.com
> > > -- 
> > > 0-DAY CI Kernel Test Service
> > > https://github.com/intel/lkp-tests/wiki
> > 
> > 
> > commit 2d6142ce44dca77fb173bb96850634b169277214
> > Author: Paul E. McKenney <paulmck@...nel.org>
> > Date:   Thu Aug 28 12:56:42 2025 -0700
> > 
> >     EXP tracing: Diagnostic for __DECLARE_TRACE() use of SRCU-fast
> >     
> >     This patch is intended to test the theory that preemption needs to be
> >     disabled in some portion of the tracing infrastructure extending from
> >     the __DECLARE_TRACE() macro to the target BPF program.
> >     
> >     Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
> > 
> > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> > index a22c1ab88560b8..c422e4c5ed51ed 100644
> > --- a/include/linux/tracepoint.h
> > +++ b/include/linux/tracepoint.h
> > @@ -273,7 +273,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
> >  	static inline void __do_trace_##name(proto)			\
> >  	{								\
> >  		if (cond) {						\
> > -			guard(srcu_fast_notrace)(&tracepoint_srcu);	\
> > +			guard(preempt_notrace)();			\
> >  			__DO_TRACE_CALL(name, TP_ARGS(args));		\
> >  		}							\
> >  	}								\