linux-kernel - Re: [PATCH] uprobes: fix incorrect lockdep condition in filter

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Message-ID: <aXpMhBIc6qBd5poV@gmail.com>
Date: Wed, 28 Jan 2026 09:51:20 -0800
From: Breno Leitao <leitao@...ian.org>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>, 
	Masami Hiramatsu <mhiramat@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
	Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>, 
	Adrian Hunter <adrian.hunter@...el.com>, James Clark <james.clark@...aro.org>, 
	Andrii Nakryiko <andrii@...nel.org>, linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, kernel-team@...a.com, stable@...r.kernel.org
Subject: Re: [PATCH] uprobes: fix incorrect lockdep condition in
 filter_chain()

On Wed, Jan 28, 2026 at 09:23:45AM -0800, Andrii Nakryiko wrote:
> On Wed, Jan 28, 2026 at 5:51 AM Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > On 01/28, Breno Leitao wrote:
> > >
> > > The list_for_each_entry_rcu() in filter_chain() uses
> > > rcu_read_lock_trace_held() as the lockdep condition, but the function
> > > holds consumer_rwsem, not the RCU trace lock.
> > >
> > > This gives me the following output when running with some locking debug
> > > option enabled:
> > >
> > >   kernel/events/uprobes.c:1141 RCU-list traversed in non-reader section!!
> > >     filter_chain
> > >     register_for_each_vma
> > >     uprobe_unregister_nosync
> > >     __probe_event_disable
> > >
> > > Remove the incorrect lockdep condition since the rwsem provides
> > > sufficient protection for the list traversal.
> >
> > I hope Andrii will recheck, but looks obviously correct to me.
> 
> yeah, I did, and it also looks obviously correct to me, I didn't need
> to use rcu flavor there in the first place, I think.
> 
> Acked-by: Andrii Nakryiko <andrii@...nel.org>
> 
> >
> > > Fixes: 87195a1ee332a ("uprobes: switch to RCU Tasks Trace flavor for better performance")
> >
> > This commit just change the __list_check_rcu() condition...
> >
> > Perhaps
> > Fixes: cc01bd044e6a ("uprobes: travers uprobe's consumer list locklessly under SRCU protection")
> >
> 
> yep, this one is the earliest change adding unnecessary rcu flavor of
> list_for_each_entry

Ack. I will respin with the correct "fixes" tag.

--breno