linux-kernel - Re: [PATCH] tracing: Fix tracing_marker may trigger page fault during preempt

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Message-Id: <20250902010115.e20bb3beb9341aa5cb651009@kernel.org>
Date: Tue, 2 Sep 2025 01:01:15 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Luo Gengkun
 <luogengkun@...weicloud.com>, mhiramat@...nel.org,
 mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, Will Deacon <will@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, Mark Rutland <mark.rutland@....com>,
 Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] tracing: Fix tracing_marker may trigger page fault
 during preempt_disable

On Fri, 29 Aug 2025 18:13:11 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Fri, 29 Aug 2025 20:53:40 +0100
> Catalin Marinas <catalin.marinas@....com> wrote:
> valid user address.
> > 
> > BTW, arm64 also bails out early in do_page_fault() if in_atomic() but I
> > suspect that's not the case here.
> > 
> > Adding Al Viro since since he wrote a large part of uaccess.h.
> > 
> 
> So, __copy_from_user_inatomic() is supposed to be called if
> pagefault_disable() has already been called? If this is the case, can we
> add more comments to this code? I've been using the inatomic() version this
> way in preempt disabled locations since 2016.

Ah, OK. it is internal version... plz ignore my previous mail.

Thanks,

> 
> Looks like it needs to be converted to copy_from_user_nofault().
> 
> Luo, this version of the patch looks legit, no need for a v2.
> 
> I just wanted to figure out why __copy_from_user_inatomic() wasn't atomic.
> If anything, it needs to be better documented.
> 
> -- Steve


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>