linux-kernel - Re: [RFC PATCH v4 4/4] tracing: Add might_fault() check in __DO

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Message-ID: <CADKFtnT59wzKxob03OOOfvVh67MQkpWvzvfmzv3D-_bGeM=rJA@mail.gmail.com>
Date: Mon, 28 Oct 2024 13:40:26 -0700
From: Jordan Rife <jrife@...gle.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>, Steven Rostedt <rostedt@...dmis.org>, 
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, 
	Michael Jeanson <mjeanson@...icios.com>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>, Alexei Starovoitov <ast@...nel.org>, Yonghong Song <yhs@...com>, 
	"Paul E . McKenney" <paulmck@...nel.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Namhyung Kim <namhyung@...nel.org>, 
	bpf@...r.kernel.org, Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [RFC PATCH v4 4/4] tracing: Add might_fault() check in
 __DO_TRACE() for syscall

> I'm still awaiting for Jordan (or someone else) to come back with
testing results before I feel confident dropping the RFC tag.

I can test this later today. Considering there needs to be a fix on
the BPF side to fully resolve the use-after-free issue reported by
syzbot, I may combine your v4 patch with the bandaid fix which chains
call_rcu->call_rcu_tasks_trace I made earlier while running the
reproducer locally. This should give some confidence that your patch
addresses issues on the tracepoint side until we can combine it with
Andrii's fix for BPF that consumes tracepoint_is_faultable(). I'm open
to other suggestions as well if you would like me to test something
else.

-Jordan